RELATED APPLICATIONS

The present application is related to U.S patent application Ser. Nos. 10/043,018 and 10/042,901, filed on Jan. 8, 2002 concurrently with, and assigned to the same assignee, as the present application.

FIELD OF THE INVENTION

This invention relates generally to computer graphics, and more particularly to virtualizing resources for computer graphics.

COPYRIGHT NOTICE/PERMISSION

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the software and data as described below and in the drawings hereto: Copyright© 1999-2002, Apple Computer, Inc., All Rights Reserved.

BACKGROUND OF THE INVENTION

A graphics kernel driver typically interfaces between graphics client drivers and graphics hardware to assign graphics resources to each client driver and to administer the submission of graphics commands to the graphics hardware. Each client driver has explicit knowledge of the graphics resources it is assigned and references the resources in its commands using the physical address of the resources. As more sophisticated graphics features are developed, the demand for graphics resources is ever increasing but the graphics resources are limited by the graphics hardware and other system constraints. The assigned resources cannot be shared among clients because the graphics hardware is not designed to handle resource contention among the clients. Additionally, the client drivers are required to manage their own internal resource conflicts. For example, they must handle their attempts to use more than available graphics memory.

SUMMARY OF THE INVENTION

Graphics resources are virtualized through an interface between graphics hardware and graphics clients. The interface allocates the graphics resources across multiple graphics clients, processes commands for access to the graphics resources from the graphics clients, and resolves conflicts for the graphics resources among the clients.

In one aspect, the interface is a graphics kernel that assigns an identifier to a resource when allocated by a graphics client and the client uses the identifier instead of an address for the resource when requesting access to the resource.

Because the native command structure for the graphics hardware is unaffected by the virtualization, neither the applications nor the hardware require modification to operate in conjunction with the present invention. Furthermore, because the virtualized resources appear as unlimited resources to the graphics clients, the clients can be simplified since, for example, they are no longer required to de-fragment or compact their assigned resources.

The present invention describes systems, methods, and machine-readable media of varying scope. In addition to the aspects of the present invention described in this summary, further aspects of the invention will become apparent by reference to the drawings and by reading the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A

is a diagram illustrating a graphics driver stack that incorporates the present invention;

FIG. 1B

is a diagram illustrating a system overview of one embodiment of processing in the driver stack of

FIG. 1A

;

FIGS. 2A-B

illustrate graphics command streams according to one embodiment of the invention;

FIGS. 3A-C

illustrate processing of command buffers according to embodiments of the invention;

FIG. 4A

is a flowchart of a graphics client driver method to be performed by a computer processor according to an embodiment of the invention;

FIG. 4B

is a flowchart of a graphics kernel driver method to be performed by a graphics processor according to an embodiment of the invention;

FIG. 5A

is a diagram of one embodiment of an operating environment suitable for practicing the present invention; and

FIG. 5B

is a diagram of one embodiment of a computer system suitable for use in the operating environment of FIG.

5

A.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of embodiments of the invention, reference is made to the accompanying drawings in which like references indicate similar elements, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, functional, and other changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

In one embodiment, the present invention is integrated into a graphics driver stack

100

as illustrated in

FIG. 1A. A

graphics kernel driver

101

interfaces between graphics client drivers

103

,

105

,

107

,

109

and graphics hardware

111

to virtualize limited graphics resources used by the graphics hardware

111

and manage contention among the client drivers for the resources. The virtualized resources appear as unlimited resources to the client drivers, which allows the client drivers to be simplified since, for example, they are no longer required to de-fragment or compact their assigned memory.

Graphics resources eligible for virtualization include any limited resource used by the graphics hardware

111

, such as graphics memory, either integrated in the graphics hardware

111

or allocated in system memory, GART (graphics address re-mapping table) entries, memory apertures for accessing video memory or registers, specialized memory areas for hierarchical depth buffers, among others. For the sake of clarity, the virtualization of graphics memory is used as an example throughout, but the invention is not so limited.

Referring now to an exemplary embodiment shown in

FIG. 1B

, the kernel driver

101

manages the allocation of memory among clients through a virtualization map

117

, such as a range allocation table. The virtualization map

117

indicates how graphics memory is currently allocated, including which block a client is using.

An application

115

calls an OpenGL engine

113

through an OpenGL API (application program interface)

119

to create an image. The OpenGL engine

113

, executing on the central processing unit (CPU) of the computer, determines how to divide the image processing work between the CPU and the graphics processor of the graphics hardware

111

, and sends the commands to be processed by the graphics processor to the OpenGL client driver

103

through a client driver API

121

. The client driver

103

, also executing on the CPU, evaluates the commands and determines that it needs graphics memory to create the image. The client driver

103

requests a block of memory from the kernel driver

101

through a kernel driver API call

123

. The kernel driver

101

, executing on the graphics processor, records the request in an entry in the virtualization map

117

, and associates an identifier with the entry. The kernel driver

101

returns the identifier to the client driver

103

for use in all commands that access the memory block. Because the native command structure for OpenGL and the graphics hardware is unaffected by the virtualization, neither the application

115

, the OpenGL engine

113

, nor the hardware

111

require modification to operate in conjunction with the present invention.

In one embodiment, the kernel driver

101

performs the actual physical allocation of memory when the client driver

103

submits a command that references the identifier. In another embodiment, the kernel driver

101

physically allocates the memory upon receiving the allocation request. In either case, when all physical memory is already allocated, the kernel driver

101

pages a corresponding amount of data currently in memory to a backing store and updates the virtualization map

117

. The kernel driver

101

uses the virtualization map

117

to determine how to page the data back into memory for subsequent processing. Details of the paging are described further below in conjunction with FIG.

4

B.

In one embodiment, the identifier is a “token” that represents the memory block and the client driver

103

creates tokenized commands by substituting the token for the memory address. When the client driver

103

submits a tokenized command to the graphics hardware

111

, the kernel driver

101

extracts the token, finds the address of the memory block represented by the token in the virtualization map

117

, and replaces the token with the real address. When the tokenized commands are submitted as part of a standard graphics command stream, the kernel driver

101

must parse the stream into its individual commands and evaluate most, if not all, the commands to determine which contain tokens. This can be a slow and expensive operation.

Therefore, in another embodiment, the client driver

103

formats the command stream as illustrated in

FIG. 2B. A

command stream

200

contains standard commands

203

,

205

, followed by a tokenized command

207

, followed by various other commands, and terminates with a tokenized command

209

. The stream

200

is prefaced with a “jump” packet

201

that points to the first tokenized command

207

in the stream

200

. The tokenized command

207

contains another jump packet that points to the next tokenized command in the stream

200

, and so on until the last jump packet in the stream is reached. The jump packets thus create a linked list of tokenized commands, allowing the kernel driver

101

to ignore the standard commands in the stream

200

without having to evaluate each command individually.

In one embodiment, the jump packets contain a packet type and an offset value relative to the current packet. Assuming a command stream

210

as illustrated in

FIG. 2B

, the kernel driver

101

reads the first command in the stream, which is a “start” jump packet

211

. The kernel driver

101

extracts the offset value from the start jump packet

211

and deletes the packet from the stream. The kernel driver

101

uses the offset value to jump to the next jump packet

219

, which is in the “load texture” command

217

. The kernel driver

101

extracts the next offset value and packet type from the jump packet

219

. The packet type identifies the packet

219

as a “texture” packet, indicating that the token

221

represents a block of memory containing texture data. The kernel driver

101

replaces the tokenized command

217

with a valid graphics command

225

containing the memory address

223

corresponding to the token

221

, and jumps to the jump packet in the next tokenized command in the stream. The resulting stream

220

received by the graphics hardware

111

contains “polygon”

213

and “change state”

215

commands unchanged from the stream

210

submitted by the client driver

103

, and a “load texture” command

225

as modified by the kernel driver

101

. Thus, the final processing of the command stream by the kernel driver only requires each jump packet to be read and written to and from memory while the majority of the command data generated by the client driver is not read or interpreted by the kernel driver.

Alternate embodiments in which the jump packets are not embedded in the tokenized commands in the stream or are submitted as a separate stream associated with the command stream are contemplated as within the scope of the invention.

When a particular region of graphics memory requested by a current client driver has been reused by a previous client driver, the kernel driver completes the use of the memory by the previous client driver, and prepares the resource for use by the current client driver. When the kernel driver processes a tokenized command, the graphics memory referenced by the token may be in one of two states: valid for immediate use by the client driver or not. If the memory is valid for immediate use, the kernel driver proceeds as previously described. If the memory is not valid for immediate use, the kernel driver refreshes the current client's data by allocating a new region of graphics memory and page the data into it. Before doing this however, the kernel driver submits all graphics commands in the current client's command stream up to the current jump packet to the graphics hardware before it starts allocating the new region of graphics memory for the current client because the process of allocation might result in the deallocation and paging of graphics memory previously referenced in the current command stream. Details of the refreshing of data are described further below in conjunction with FIG.

4

B.

Command buffers are commonly used to hold the command streams from multiple clients. As shown in

FIG. 3A

, as the client driver generates commands, the CPU fills the appropriate buffer

301

,

303

. When a buffer is full, it is placed in a processing queue for the graphics hardware, and the CPU assigns another buffer to the client driver. It will be appreciated that when jump packets are used, the client driver loads the start jump packet first in the buffer.

The command buffers allow multiple clients to create streams asynchronously to each other. The command buffers also allow the graphics hardware and the CPU to operate asynchronously, keeping both busy even though they typically operate at different speeds.

In one embodiment, the queued buffers are arranged as a linked list as shown in FIG.

3

B. The contents of the buffers

301

,

303

,

305

are read by the graphics hardware

111

as a linear stream of commands for execution in a serialized fashion, i.e., all the commands in one buffer are executed before the commands in the next buffer in the queue. The serialized, linear execution by the graphics hardware

111

provides the kernel driver

101

with an memory management timeline to follow in processing the commands that reference graphics memory. After processing by the kernel driver, the entire command stream is valid for consumption by the graphics hardware since the conflicts between clients due to reuse of memory have been resolved and the jump packets and tokenized commands have been replaced with valid graphics hardware commands.

In an alternate embodiment, the identifier for the memory block allocated to the client driver

103

is the physical address of the memory. Because the client expects memory address to be unchanged until it de-allocates the memory, the kernel driver

101

employs special graphics hardware features to manage the virtualization of memory. In one embodiment, the kernel driver

101

uses graphics semaphores that cause the graphics hardware to suspend processing of one buffer and switch to processing another buffer, thus interleaving the processing of the command buffers from different clients, and creating multiple inter-dependent linear timelines as illustrated in FIG.

3

C.

For example, assume client A places a command in buffer

307

that references memory also used by client C. When the kernel driver

101

reaches that command in buffer

307

, it inserts a reference to semaphore

313

before the command, effectively dividing the buffer

307

into command sequences

311

,

315

. The graphics hardware

111

processes command sequence

311

in buffer

307

until it reaches semaphore

313

, which directs it to switch to processing the next queued buffer

309

. While the graphics hardware

111

is processing buffer

309

, the kernel driver

101

pages the appropriate data back in and clears the semaphore

313

.

Similarly, assume client B places a command in buffer

309

that references memory also used by client D, so the kernel driver

101

inserts a reference to semaphore

321

in buffer

309

, creating command sequences

319

,

323

. When the graphics hardware

111

reaches semaphore

321

, it determines that semaphore

313

is clear and resumes processing buffer

307

at command sequence

315

. Because the kernel driver

101

has cleared semaphore

321

by the time the graphics hardware finishes processing command sequence

315

, the graphics hardware can now process command sequence

323

.

Next, the particular methods of the invention are described in terms of computer software with reference to a series of flowcharts. The methods to be performed by a processing system constitute computer programs made up of executable instructions illustrated as blocks (acts). Describing the methods by reference to a flowchart enables one skilled in the art to develop such programs including such instructions to carry out the methods on suitably configured hardware (the processing unit of the hardware executing the instructions from machine-readable media). The executable instructions may be written in a computer programming language or may be embodied in firmware logic. If written in a programming language conforming to a recognized standard, such instructions can be executed on a variety of hardware platforms and interface to a variety of operating systems. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. Furthermore, it is common in the art to speak of software, in one form or another (e.g., program, procedure, process, application, module, logic . . . ), as taking an action or causing a result. Such expressions are merely a shorthand way of saying that execution of the software by a machine causes the processor of the machine to perform an action or produce a result. It will be further appreciated that more or fewer processes may be incorporated into the methods illustrated in

FIGS. 4A-B

without departing from the scope of the invention and that no particular order is implied by the arrangement of blocks shown and described herein.

Referring first to

FIG. 4A

, the acts to be performed by a computer processor executing a client driver method

400

that tokenizes commands are shown. The client driver method

400

receives an image command (block

401

) and determines if graphics resources are required to process the command (block

403

). If the necessary resources have not been previously allocated, the method

400

requests the resources from the kernel driver (block

405

) and receives a token in return (block

407

). The method

400

creates the graphics commands to perform the image command at block

409

. The processing represented by block

409

includes creating the jump packets with the appropriate offsets and packet types, and inserting the jump packets and tokens in the commands. The particular packet types used by embodiments of the invention are dictated by the command set of the underlying graphics hardware. One exemplary set of packet types, called “op codes,” for graphics memory are shown in Table 1.

TABLE 1

Op Code

Remarks

kGLStreamStart

Start the stream

kGLStreamEnd

Terminate the stream

kGLStreamCopyColor

Copy an image between two draw buffers

kGLStreamCopyColor

Copy an image between two draw buffers with

Scale

scaling

kGLStreamDrawColor

Draw an image to the current draw buffer

kGLStreamTexture0

Set the current texture object on texture unit zero

kGLStreamTexture1

Set the current texture object on texture unit one

kGLStreamTexture2

Set the current texture object on texture unit two

kGLStreamTexture3

Set the current texture object on texture unit three

kGLStreamNoTex0

Remove any texture from texture unit zero

kGLStreamNoTex1

Remove any texture from texture unit one

kGLStreamNoTex2

Remove any texture from texture unit two

kGLStreamNoTex3

Remove any texture from texture unit three

kGLStreamVertex

Set the current vertex object

Buffer

kGLStreamNoVertex

Remove any current vertex object

Buffer

If there is no existing command buffer (block

411

), the method

400

starts a new buffer (block

413

) and inserts a start jump packet at the beginning of the buffer (block

415

) with an offset to the first tokenized command in the buffer. Each graphics command is loaded in the buffer (block

417

) until all graphics commands are buffered (block

419

) or the current buffer is full (block

421

). If the current buffer is full and more commands need to be buffered, the method

400

returns to block

413

to start a new buffer.

Referring now to

FIG. 4B

, the acts to be performed by a graphics processor executing a kernel driver method

430

corresponding to the client driver method

400

are shown. The kernel driver method

430

is illustrated as two parallel processing threads, one that interfaces with the client driver (starting at block

431

) and one that interfaces with the graphics hardware (starting at block

451

). It will be appreciated that the invention is not limited to such parallel processing implementations.

When the method

430

receives an allocation request from a client driver (block

431

), it determines if the requested amount of resource is available (block

433

). If not, the method

430

pages out a sufficient amount of data belonging to another client (block

435

). The method

430

allocates the resource, including assigning a token and updating its memory management information, such as the virtualization map

117

illustrated in FIG.

1

B. The token is returned to the requesting client driver at block

439

. The client driver method

430

waits until another request is received (block

441

) and returns to block

431

to process the new request.

When the client driver submits a buffer of commands to the graphics hardware for processing, the kernel driver method

430

extracts the offset and type from the next jump packet in the buffer (block

451

). If the next jump packet is the first jump packet, i.e., a start jump packet (block

453

), the method

430

deletes the start jump packet from the buffer (block

461

) and jumps to the jump packet defined by the offset (block

465

) to continue processing. Otherwise, the method

430

uses the jump packet type to locate the token in the command and determines if the resource corresponding to the token has been reused (block

455

). If so, the kernel driver method

430

refreshes the data required by the current command (block

457

). Because of the abstraction provided by the token, the kernel driver can page the data into a different available graphics resource or page out the data currently in the original resource and page in the data required by the current command. The token is replaced with the address of the resource (block

459

) and the jump packet is deleted (block

461

). If the current jump packet is the last in the buffer (block

463

), the method

430

waits for another buffer (block

467

) and returns to block

451

to process the new buffer. Otherwise, the next jump packet in the buffer is processed.

In an alternate embodiment, the processing represented by block

437

is a logical allocation of the resource to the client driver and the processing represented by blocks

433

through

435

is not performed. The kernel driver method

430

performs the physical allocation, and any necessary paging, when it encounters the first tokenized command that references the resource in the command buffer.

In one embodiment, the kernel driver method

430

uses system memory as its backing store for data that must be paged out of the virtualized graphics resources. The method

430

can request the CPU read the data into system memory, or it can request the graphics hardware to write the data to the system memory. The latter operation can be performed asynchronously with the CPU, but not all graphics hardware may be able to perform the operation or there may be incompatibilities between the graphics hardware and the CPU. When the operating system virtualizes system memory, the operating system may further page the data to mass storage. It will be appreciated that once the data has been written to system memory, a virtual memory operating system may further page the data to mass storage.

In one embodiment, what data to page into system memory is determined by various paging criteria, such as type of graphics resource, priority, and paging algorithm. Some resources, like graphics memory, are very expensive to page because the data contained in the graphics memory often must be copied into system memory. The priorities may be allocated within graphics resources types. For example, texture objects generally have a lower priority than frame buffers when paging graphics memory. Other resources, like GART entries may be paged inexpensively because the paging only requires the modification of the GART table, i.e., no data is actually relocated. Because the relative cost of paging different types of resources is quite different, different paging algorithms are used for each.

For example, when a client driver requests an allocation of graphics memory but there is not enough free contiguous memory to service the request, all graphics memory resources owned by all clients are candidates for paging. The first resources selected are owned by other clients because there may be an arbitrarily long period of time before the other clients are run again. When considering graphics memory owned by the requesting client driver, the kernel driver uses an algorithm that dynamically switches from LRU (least recently used) to MRU (most recently used) based on whether or not the client driver is overcommitted in its texture usage. An overcommitted application is an application that uses more texture memory in rendering a single frame than can be supplied by the graphics hardware. When a client driver that is not overcommitted runs out of graphics memory it is because some user input has caused the client driver to render a new scene so the LRU algorithm is used, based on the assumption that the least recently used memory resources may never be used again. When a client driver that is overcommitted runs out of graphics memory this means that it will do so cyclicly every frame, so the MRU algorithm is chosen because an LRU algorithm would result in every memory resource owned by the client driver being paged one or more times per frame.

GART entry paging is managed differently because the cost of changing GART entries is essentially unrelated to the size of the memory resource. The first candidates for paging are GART entries that may never be used again. For example, graphics memory texture objects each have a GART entry that was used to transfer the texture from system memory to graphics memory. Once the texture has been moved to graphics memory, the GART entry will never be used again unless the texture is paged from graphics memory and then reloaded. Therefore, it is likely that choosing such a GART entry for paging will have no performance cost. The remaining GART entries are categorized from highest to lowest priority for paging, with the lowest priority assigned to the GART entry for each client's command buffer, which must be mapped into GART for the client driver to use the graphics hardware at all.

One of skill in the art will appreciate that other types of graphics resources may have different algorithms for selecting which resources are candidates for paging that allow the resources to be transparently managed with respect to multiple clients as described above for graphics memory and GART.

In one embodiment, the kernel driver method

430

uses a collection of data objects, each of which represents an allocated resource, as a virtualization map. The tokens identify the data objects within the virtualization map. Each data object contains the address range for the corresponding resource. When the data in the resource is paged out, a “dirty” flag is set and a pointer to the backing store holding the data is stored in the object. It will be appreciated that the layer of abstraction between the client and the physical resources provided by the token allows the data to be paged into a resource address different than it previously occupied without the client driver being aware of the change.

The following description of

FIGS. 5A-B

is intended to provide an overview of computer hardware and other operating components suitable for performing the methods of the invention described above, but is not intended to limit the applicable environments. One of skill in the art will immediately appreciate that the invention can be practiced with other processing system configurations, including hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, and the like. The invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network.

FIG. 5A

shows several computer systems that are coupled together through a network

3

, such as the Internet. The term “Internet” as used herein refers to a network of networks which uses certain protocols, such as the TCP/IP protocol, and possibly other protocols such as, for example, the hypertext transfer protocol (HTTP) for hypertext markup language (HTML) documents that make up the World Wide Web (web). The physical connections of the Internet and the protocols and communication procedures of the Internet are well known to those of skill in the art. Access to the Internet

3

is typically provided by Internet service providers (ISP), such as the ISPs

5

and

7

. Users on client systems, such as client computer systems

21

,

25

,

35

, and

37

obtain access to the Internet through the Internet service providers, such as ISPs

5

and

7

. Access to the Internet allows users of the client computer systems to exchange information, receive and send e-mails, and view documents, such as documents which have been prepared in the HTML format. These documents are often provided by web servers, such as web server

9

which is considered to be “on” the Internet. Often these web servers are provided by the ISPs, such as ISP

5

, although a computer system can be set up and connected to the Internet without that system being also an ISP as is well known in the art.

The web server

9

is typically at least one computer system which operates as a server computer system and is configured to operate with the protocols of the World Wide Web and is coupled to the Internet. Optionally, the web server

9

can be part of an ISP which provides access to the Internet for client systems. The web server

9

is shown coupled to the server computer system

11

which itself is coupled to web content

10

, which can be considered a form of a media database. It will be appreciated that while two computer systems

9

and

11

are shown in

FIG. 5A

, the web server system

9

and the server computer system

11

can be one computer system having different software components providing the web server functionality and the server functionality provided by the server computer system

11

which will be described further below.

Client computer systems

21

,

25

,

35

, and

37

can each, with the appropriate web browsing software, view HTML pages provided by the web server

9

. The ISP

5

provides Internet connectivity to the client computer system

21

through the modem interface

23

which can be considered part of the client computer system

21

. The client computer system can be a personal computer system, a network computer, a Web TV system, or other such computer system. Similarly, the ISP

7

provides Internet connectivity for client systems

25

,

35

, and

37

, although as shown in

FIG. 5A

, the connections are not the same for these three computer systems. Client computer system

25

is coupled through a modem interface

27

while client computer systems

35

and

37

are part of a LAN. While

FIG. 5A

shows the interfaces

23

and

27

as generically as a “modem,” it will be appreciated that each of these interfaces can be an analog modem, ISDN modem, cable modem, satellite transmission interface (e.g. “Direct PC”), or other interfaces for coupling a computer system to other computer systems. Client computer systems

35

and

37

are coupled to a LAN

33

through network interfaces

39

and

41

, which can be Ethernet network or other network interfaces. The LAN

33

is also coupled to a gateway computer system

31

which can provide firewall and other Internet related services for the local area network. This gateway computer system

31

is coupled to the ISP

7

to provide Internet connectivity to the client computer systems

35

and

37

. The gateway computer system

31

can be a conventional server computer system. Also, the web server system

9

can be a conventional server computer system.

Alternatively, as well-known, a server computer system

43

can be directly coupled to the LAN

33

through a network interface

45

to provide files

47

and other services to the clients

35

,

37

, without the need to connect to the Internet through the gateway system

31

.

FIG. 5B

shows one example of a conventional computer system that can be used as a client computer system or a server computer system or as a web server system. It will also be appreciated that such a computer system can be used to perform many of the functions of an Internet service provider, such as ISP

5

. The computer system

51

interfaces to external systems through the modem or network interface

53

. It will be appreciated that the modem or network interface

53

can be considered to be part of the computer system

51

. This interface

53

can be an analog modem, ISDN modem, cable modem, token ring interface, satellite transmission interface (e.g. “Direct PC”), or other interfaces for coupling a computer system to other computer systems. The computer system

51

includes a processing unit

55

, which can be a conventional microprocessor such as an Intel Pentium microprocessor or Motorola Power PC microprocessor. Memory

59

is coupled to the processor

55

by a bus

57

. Memory

59

can be dynamic random access memory (DRAM) and can also include static RAM (SRAM). The bus

57

couples the processor

55

to the memory

59

and also to non-volatile storage

65

and to display controller

61

and to the input/output (I/O) controller

67

. The display controller

61

controls a display on a display device

63

, such as, for example, a cathode ray tube (CRT) or liquid crystal display, in accordance with the present invention. The input/output devices

69

can include a keyboard, disk drives, printers, a scanner, and other input and output devices, including a mouse or other pointing device. The display controller

61

and the I/O controller

67

can be implemented with conventional well known technology. A digital image input device

71

can be a digital camera which is coupled to an I/O controller

67

in order to allow images from the digital camera to be input into the computer system

51

. The non-volatile storage

65

is often a magnetic hard disk, an optical disk, or another form of storage for large amounts of data. Some of this data is often written, by a direct memory access process, into memory

59

during execution of software in the computer system

51

. One of skill in the art will immediately recognize that the terms “machine-readable medium” and “computer-readable medium” includes any type of storage device that is accessible by the processor

55

and also encompasses a carrier wave that encodes a data signal.

It will be appreciated that the computer system

51

is one example of many possible computer systems which have different architectures. For example, personal computers based on an Intel microprocessor often have multiple buses, one of which can be an input/output (I/O) bus for the peripherals and one that directly connects the processor

55

and the memory

59

(often referred to as a memory bus). The buses are connected together through bridge components that perform any necessary translation due to differing bus protocols.

Network computers are another type of computer system that can be used with the present invention. Network computers do not usually include a hard disk or other mass storage, and the executable programs are loaded from a network connection into the memory

59

for execution by the processor

55

. A Web TV system, which is known in the art, is also considered to be a computer system according to the present invention, but it may lack some of the features shown in

FIG. 5B

, such as certain input or output devices. A typical computer system will usually include at least a processor, memory, and a bus coupling the memory to the processor.

It will also be appreciated that the computer system

51

is controlled by operating system software which includes a file management system, such as a disk operating system, which is part of the operating system software. One example of an operating system software with its associated file management system software is the family of operating systems known as Mac® from Apple Computer, Inc. of Cupertino, Calif., and their associated file management systems. The file management system is typically stored in the non-volatile storage

65

and causes the processor

55

to execute the various acts required by the operating system to input and output data and to store data in memory, including storing files on the non-volatile storage

65

.

Virtualization of graphics resources has been described. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention. The terminology used in this application with respect to graphics is meant to include all environments that display images to a user. Therefore, it is manifestly intended that this invention be limited only by the following claims and equivalents thereof.