R
R420
http://www.beyond3d.com/forum/viewtopic.php?t=13470
http://forums.xbox-scene.com/index.php?showtopic=231928
Xenon Hardware Overview
By Pete Isensee, Development Lead, Xbox Advanced Technology Group
This documentation is an early release of the final documentation,
which may be changed substantially prior to final commercial release,
and is confidential and proprietary information of MS Corporation. It
is disclosed pursuant to a nondisclosure agreement between the
recipient and MS.
"Xenon" is the code name for the successor to the Xbox® game console
from MS. Xenon is expected to launch in 2005. This white paper is
designed to provide a brief overview of the primary hardware features
of the console from a game developer's standpoint.
Caveats
In some cases, sizes, speeds, and other details of the Xenon console
have not been finalized. Values not yet finalized are identified with
a "+" sign, indicating that the numbers may be larger than indicated
here. At the time of this writing, the final console is many months
from entering production. Based on our experience with Xbox, it's
likely that some of this information will change slightly for the
final console.
For additional information on various hardware components, see the
other relevant white papers.
Hardware Goals
Xenon was designed with the following goals in mind:
•Focus on innovation in silicon, particularly features that game
developers need. Although all Xenon hardware components are
technologically advanced, the hardware engineering effort has
concentrated on digital performance in the CPU and GPU.
•Maximize general purpose processing performance rather than
fixed-function hardware. This focus on general purpose processing puts
the power into the Xenon software libraries and tools. Rather than
being hamstrung by particular hardware designs, software libraries can
support the latest and most efficient techniques.
•Eliminate the performance issues of the past. On Xbox, the primary
bottlenecks were memory and CPU bandwidth. Xenon does not have these
limitations.
Basic Hardware Specifications
Xenon is powered by a 3.5+ GHz IBM PowerPC processor and a 500+ MHz
ATI graphics processor. Xenon has 256+ MB of unified memory. Xenon
runs a custom operating system based on MS® Windows NT®, similar to
the Xbox operating system. The graphics interface is a superset of MS®
Direct3D® version 9.0.
CPU
The Xenon CPU is a custom processor based on PowerPC technology. The
CPU includes three independent processors (cores) on a single die.
Each core runs at 3.5+ GHz. The Xenon CPU can issue two instructions
per clock cycle per core. At peak performance, Xenon can issue 21
billion instructions per second.
The Xenon CPU was designed by IBM in close consultation with the Xbox
team, leading to a number of revolutionary additions, including a dot
product instruction for extremely fast vector math and custom security
features built directly into the silicon to prevent piracy and
hacking.
Each core has two symmetric hardware threads (SMT), for a total of six
hardware threads available to games. Not only does the Xenon CPU
include the standard set of PowerPC integer and floating-point
registers (one set per hardware thread), the Xenon CPU also includes
128 vector (VMX) registers per hardware thread. This astounding number
of registers can drastically improve the speed of common mathematical
operations.
Each of the three cores includes a 32-KB L1 instruction cache and a
32-KB L1 data cache. The three cores share a 1-MB L2 cache. The L2
cache can be locked down in segments to improve performance. The L2
cache also has the very unusual feature of being directly readable
from the GPU, which allows the GPU to consume geometry and texture
data from L2 and main memory simultaneously.
Xenon CPU instructions are exposed to games through compiler
intrinsics, allowing developers to access the power of the chip using
C language notation.
GPU
The Xenon GPU is a custom 500+ MHz graphics processor from ATI. The
shader core has 48 Arithmetic Logic Units (ALUs) that can execute 64
simultaneous threads on groups of 64 vertices or pixels. ALUs are
automatically and dynamically assigned to either pixel or vertex
processing depending on load. The ALUs can each perform one vector and
one scalar operation per clock cycle, for a total of 96 shader
operations per clock cycle. Texture loads can be done in parallel to
ALU operations. At peak performance, the GPU can issue 48 billion
shader operations per second.
The GPU has a peak pixel fill rate of 4+ gigapixels/sec (16
gigasamples/sec with 4× antialiasing). The peak vertex rate is 500+
million vertices/sec. The peak triangle rate is 500+ million
triangles/sec. The interesting point about all of these values is that
they're not just theoretical—they are attainable with nontrivial
shaders.
Xenon is designed for high-definition output. Included directly on the
GPU die is 10+ MB of fast embedded dynamic RAM (EDRAM). A 720p frame
buffer fits very nicely here. Larger frame buffers are also possible
because of hardware-accelerated partitioning and predicated rendering
that has little cost other than additional vertex processing. Along
with the extremely fast EDRAM, the GPU also includes hardware
instructions for alpha blending, z-test, and antialiasing.
The Xenon graphics architecture is a unique design that implements a
superset of Direct3D version 9.0. It includes a number of important
extensions, including additional compressed texture formats and a
flexible tessellation engine. Xenon not only supports high-level
shading language (HLSL) model 3.0 for vertex and pixel shaders but
also includes advanced shader features well beyond model 3.0. For
instance, shaders use 32-bit IEEE floating-point math throughout.
Vertex shaders can fetch from textures, and pixel shaders can fetch
from vertex streams. Xenon shaders also have the unique ability to
directly access main memory, allowing techniques that have never
before been possible.
As with Xbox, Xenon will support precompiled push buffers ("command
buffers" in Xenon terminology), but to a much greater extent than the
Xbox console does. The Xbox team is exposing and documenting the
command buffer format so that games are able to harness the GPU much
more effectively.
In addition to an extremely powerful GPU, Xenon also includes a very
high-quality resize filter. This filter allows consumers to choose
whatever output mode they desire. Xenon automatically scales the
game's output buffer to the consumer-chosen resolution.
Memory and Bandwidth
Xenon has 256+ MB of unified memory, equally accessible to both the
GPU and CPU. The main memory controller resides on the GPU (the same
as in the Xbox architecture). It has 22.4+ GB/sec aggregate bandwidth
to RAM, distributed between reads and writes. Aggregate means that the
bandwidth may be used for all reading or all writing or any
combination of the two. Translated into game performance, the GPU can
consume a 512×512×32-bpp texture in only 47 microseconds.
The front side bus (FSB) bandwidth peak is 10.8 GB/sec for reads and
10.8 GB/sec for writes, over 20 times faster than for Xbox. Note that
the 22.4+ GB/sec main memory bandwidth is shared between the CPU and
GPU. If, for example, the CPU is using 2 GB/sec for reading and 1
GB/sec for writing on the FSB, the GPU has 19.4+ GB/sec available for
accessing RAM.
Eight pixels (where each pixel is color plus z = 8 bytes) can be sent
to the EDRAM every GPU clock cycle, for an EDRAM write bandwidth of 32
GB/sec. Each of these pixels can be expanded through multisampling to
4 samples, for up to 32 multisampled pixel samples per clock cycle.
With alpha blending, z-test, and z-write enabled, this is equivalent
to having 256 GB/sec of effective bandwidth! The important thing is
that frame buffer bandwidth will never slow down the Xenon GPU.
Audio
The Xenon CPU is a superb processor for audio, particularly with its
massive mathematical horsepower and vector register set. The Xenon CPU
can process and encode hundreds of audio channels with sophisticated
per-voice and global effects, all while using a fraction of the power
of a single CPU core.
The Xenon system south bridge also contains a key hardware component
for audio—XMA decompression. XMA is the native Xenon compressed audio
format, based on the WMA Pro architecture. XMA provides sound quality
higher than ADPCM at even better compression ratios, typically
6:1–12:1. The south bridge contains a full silicon implementation of
the XMA decompression algorithm, including support for multichannel
XMA sources. XMA is processed by the south bridge into standard PCM
format in RAM. All other sound processing (sample rate conversion,
filtering, effects, mixing, and multispeaker encoding) happens on the
Xenon CPU.
The lowest-level Xenon audio software layer is XAudio, a new API
designed for optimal digital signal processing. The Xbox Audio
Creation Tool (XACT) API from Xbox is also supported, along with new
features such as conditional events, improved parameter control, and a
more flexible 3D audio model.
Input/Output
As with Xbox, Xenon is designed to be a multiplayer console. It has
built-in networking support including an Ethernet 10/100-BaseT port.
It supports up to four controllers. From an audio/video standpoint,
Xenon will support all the same formats as Xbox, including multiple
high-definition formats up through 1080i, plus VGA output.
In order to provide greater flexibility and support a wider variety of
attached devices, the Xenon console includes standard USB 2.0 ports.
This feature allows the console to potentially host storage devices,
cameras, microphones, and other devices.
Storage
The Xenon console is designed around a larger world view of storage
than Xbox was. Games will have access to a variety of storage devices,
including connected devices (memory units, USB storage) and remote
devices (networked PCs, Xbox Live™). At the time of this writing, the
decision to include a built-in hard disk in every Xenon console has
not been made. If a hard disk is not included in every console, it
will certainly be available as an integrated add-on component.
Xenon supports up to two attached memory units (MUs). MUs are
connected directly to the console, not to controllers as on Xbox. The
initial size of the MUs is 64 MB, although larger MUs may be available
in the future. MU throughput is expected to be around 8 MB/sec for
reads and 1 MB/sec for writes.
The Xenon game disc drive is a 12× DVD, with an expected outer edge
throughput of 16+ MB/sec. Latency is expected to be in the
neighborhood of 100 ms. The media format will be similar to Xbox, with
approximately 6 GB of usable space on the disk. As on Xbox, media will
be stored on a single side in two 3 GB layers.
Industrial Design
The Xenon industrial design process is well under way, but the final
look of the box has not been determined. The Xenon console will be
smaller than the Xbox console.
The standard Xenon controller will have a look and feel similar to the
Xbox controller. The primary changes are the removal of the Black and
White buttons and the addition of shoulder buttons. The triggers,
thumbsticks, D-pad, and primary buttons are essentially unchanged. The
controller will support vibration.
Xenon Development Kit
The Xenon development environment follows the same model as for Xbox.
Game development occurs on the PC. The resulting executable image is
loaded by the Xenon development kit and remotely debugged on the PC.
MS® Visual Studio® version 7.1 continues as the development
environment for Xenon.
The Xenon compiler is based on a custom PowerPC back end and the
latest MS® Visual C++® front end. The back end uses technology
developed at MS for Windows NT on PowerPC. The Xenon software group
includes a dedicated team of compiler engineers updating the compiler
to support Xenon-specific CPU extensions. This team is also heavily
focused on optimization work.
The Xenon development kit will include accurate DVD emulation
technology to allow developers to very precisely gauge the effects of
the retail console disc drive.
Miscellaneous Xenon Hardware Notes
Some additional notes:
•Xenon is a big-endian system. Both the CPU and GPU process memory in
big-endian mode. Games ported from little-endian systems such as the
Xbox or PC need to account for this in their game asset pipeline.
•Tapping into the power of the CPU is a daunting task. Writing
multithreaded game engines is not trivial. Xenon system software is
designed to take advantage of this processing power wherever possible.
The Xbox Advanced Technology Group (ATG) is also exploring a variety
of techniques for offloading graphics work to the CPU.
•People often ask if Xenon can be backward compatible with Xbox.
Although the architecture of the two consoles is quite different,
Xenon has the processing power to emulate Xbox. Whether Xenon will be
backward compatible involves a variety of factors, not the least of
which is the massive development and testing effort required to allow
Xbox games run on Xenon.
http://forums.xbox-scene.com/index.php?showtopic=231928
Xenon Hardware Overview
By Pete Isensee, Development Lead, Xbox Advanced Technology Group
This documentation is an early release of the final documentation,
which may be changed substantially prior to final commercial release,
and is confidential and proprietary information of MS Corporation. It
is disclosed pursuant to a nondisclosure agreement between the
recipient and MS.
"Xenon" is the code name for the successor to the Xbox® game console
from MS. Xenon is expected to launch in 2005. This white paper is
designed to provide a brief overview of the primary hardware features
of the console from a game developer's standpoint.
Caveats
In some cases, sizes, speeds, and other details of the Xenon console
have not been finalized. Values not yet finalized are identified with
a "+" sign, indicating that the numbers may be larger than indicated
here. At the time of this writing, the final console is many months
from entering production. Based on our experience with Xbox, it's
likely that some of this information will change slightly for the
final console.
For additional information on various hardware components, see the
other relevant white papers.
Hardware Goals
Xenon was designed with the following goals in mind:
•Focus on innovation in silicon, particularly features that game
developers need. Although all Xenon hardware components are
technologically advanced, the hardware engineering effort has
concentrated on digital performance in the CPU and GPU.
•Maximize general purpose processing performance rather than
fixed-function hardware. This focus on general purpose processing puts
the power into the Xenon software libraries and tools. Rather than
being hamstrung by particular hardware designs, software libraries can
support the latest and most efficient techniques.
•Eliminate the performance issues of the past. On Xbox, the primary
bottlenecks were memory and CPU bandwidth. Xenon does not have these
limitations.
Basic Hardware Specifications
Xenon is powered by a 3.5+ GHz IBM PowerPC processor and a 500+ MHz
ATI graphics processor. Xenon has 256+ MB of unified memory. Xenon
runs a custom operating system based on MS® Windows NT®, similar to
the Xbox operating system. The graphics interface is a superset of MS®
Direct3D® version 9.0.
CPU
The Xenon CPU is a custom processor based on PowerPC technology. The
CPU includes three independent processors (cores) on a single die.
Each core runs at 3.5+ GHz. The Xenon CPU can issue two instructions
per clock cycle per core. At peak performance, Xenon can issue 21
billion instructions per second.
The Xenon CPU was designed by IBM in close consultation with the Xbox
team, leading to a number of revolutionary additions, including a dot
product instruction for extremely fast vector math and custom security
features built directly into the silicon to prevent piracy and
hacking.
Each core has two symmetric hardware threads (SMT), for a total of six
hardware threads available to games. Not only does the Xenon CPU
include the standard set of PowerPC integer and floating-point
registers (one set per hardware thread), the Xenon CPU also includes
128 vector (VMX) registers per hardware thread. This astounding number
of registers can drastically improve the speed of common mathematical
operations.
Each of the three cores includes a 32-KB L1 instruction cache and a
32-KB L1 data cache. The three cores share a 1-MB L2 cache. The L2
cache can be locked down in segments to improve performance. The L2
cache also has the very unusual feature of being directly readable
from the GPU, which allows the GPU to consume geometry and texture
data from L2 and main memory simultaneously.
Xenon CPU instructions are exposed to games through compiler
intrinsics, allowing developers to access the power of the chip using
C language notation.
GPU
The Xenon GPU is a custom 500+ MHz graphics processor from ATI. The
shader core has 48 Arithmetic Logic Units (ALUs) that can execute 64
simultaneous threads on groups of 64 vertices or pixels. ALUs are
automatically and dynamically assigned to either pixel or vertex
processing depending on load. The ALUs can each perform one vector and
one scalar operation per clock cycle, for a total of 96 shader
operations per clock cycle. Texture loads can be done in parallel to
ALU operations. At peak performance, the GPU can issue 48 billion
shader operations per second.
The GPU has a peak pixel fill rate of 4+ gigapixels/sec (16
gigasamples/sec with 4× antialiasing). The peak vertex rate is 500+
million vertices/sec. The peak triangle rate is 500+ million
triangles/sec. The interesting point about all of these values is that
they're not just theoretical—they are attainable with nontrivial
shaders.
Xenon is designed for high-definition output. Included directly on the
GPU die is 10+ MB of fast embedded dynamic RAM (EDRAM). A 720p frame
buffer fits very nicely here. Larger frame buffers are also possible
because of hardware-accelerated partitioning and predicated rendering
that has little cost other than additional vertex processing. Along
with the extremely fast EDRAM, the GPU also includes hardware
instructions for alpha blending, z-test, and antialiasing.
The Xenon graphics architecture is a unique design that implements a
superset of Direct3D version 9.0. It includes a number of important
extensions, including additional compressed texture formats and a
flexible tessellation engine. Xenon not only supports high-level
shading language (HLSL) model 3.0 for vertex and pixel shaders but
also includes advanced shader features well beyond model 3.0. For
instance, shaders use 32-bit IEEE floating-point math throughout.
Vertex shaders can fetch from textures, and pixel shaders can fetch
from vertex streams. Xenon shaders also have the unique ability to
directly access main memory, allowing techniques that have never
before been possible.
As with Xbox, Xenon will support precompiled push buffers ("command
buffers" in Xenon terminology), but to a much greater extent than the
Xbox console does. The Xbox team is exposing and documenting the
command buffer format so that games are able to harness the GPU much
more effectively.
In addition to an extremely powerful GPU, Xenon also includes a very
high-quality resize filter. This filter allows consumers to choose
whatever output mode they desire. Xenon automatically scales the
game's output buffer to the consumer-chosen resolution.
Memory and Bandwidth
Xenon has 256+ MB of unified memory, equally accessible to both the
GPU and CPU. The main memory controller resides on the GPU (the same
as in the Xbox architecture). It has 22.4+ GB/sec aggregate bandwidth
to RAM, distributed between reads and writes. Aggregate means that the
bandwidth may be used for all reading or all writing or any
combination of the two. Translated into game performance, the GPU can
consume a 512×512×32-bpp texture in only 47 microseconds.
The front side bus (FSB) bandwidth peak is 10.8 GB/sec for reads and
10.8 GB/sec for writes, over 20 times faster than for Xbox. Note that
the 22.4+ GB/sec main memory bandwidth is shared between the CPU and
GPU. If, for example, the CPU is using 2 GB/sec for reading and 1
GB/sec for writing on the FSB, the GPU has 19.4+ GB/sec available for
accessing RAM.
Eight pixels (where each pixel is color plus z = 8 bytes) can be sent
to the EDRAM every GPU clock cycle, for an EDRAM write bandwidth of 32
GB/sec. Each of these pixels can be expanded through multisampling to
4 samples, for up to 32 multisampled pixel samples per clock cycle.
With alpha blending, z-test, and z-write enabled, this is equivalent
to having 256 GB/sec of effective bandwidth! The important thing is
that frame buffer bandwidth will never slow down the Xenon GPU.
Audio
The Xenon CPU is a superb processor for audio, particularly with its
massive mathematical horsepower and vector register set. The Xenon CPU
can process and encode hundreds of audio channels with sophisticated
per-voice and global effects, all while using a fraction of the power
of a single CPU core.
The Xenon system south bridge also contains a key hardware component
for audio—XMA decompression. XMA is the native Xenon compressed audio
format, based on the WMA Pro architecture. XMA provides sound quality
higher than ADPCM at even better compression ratios, typically
6:1–12:1. The south bridge contains a full silicon implementation of
the XMA decompression algorithm, including support for multichannel
XMA sources. XMA is processed by the south bridge into standard PCM
format in RAM. All other sound processing (sample rate conversion,
filtering, effects, mixing, and multispeaker encoding) happens on the
Xenon CPU.
The lowest-level Xenon audio software layer is XAudio, a new API
designed for optimal digital signal processing. The Xbox Audio
Creation Tool (XACT) API from Xbox is also supported, along with new
features such as conditional events, improved parameter control, and a
more flexible 3D audio model.
Input/Output
As with Xbox, Xenon is designed to be a multiplayer console. It has
built-in networking support including an Ethernet 10/100-BaseT port.
It supports up to four controllers. From an audio/video standpoint,
Xenon will support all the same formats as Xbox, including multiple
high-definition formats up through 1080i, plus VGA output.
In order to provide greater flexibility and support a wider variety of
attached devices, the Xenon console includes standard USB 2.0 ports.
This feature allows the console to potentially host storage devices,
cameras, microphones, and other devices.
Storage
The Xenon console is designed around a larger world view of storage
than Xbox was. Games will have access to a variety of storage devices,
including connected devices (memory units, USB storage) and remote
devices (networked PCs, Xbox Live™). At the time of this writing, the
decision to include a built-in hard disk in every Xenon console has
not been made. If a hard disk is not included in every console, it
will certainly be available as an integrated add-on component.
Xenon supports up to two attached memory units (MUs). MUs are
connected directly to the console, not to controllers as on Xbox. The
initial size of the MUs is 64 MB, although larger MUs may be available
in the future. MU throughput is expected to be around 8 MB/sec for
reads and 1 MB/sec for writes.
The Xenon game disc drive is a 12× DVD, with an expected outer edge
throughput of 16+ MB/sec. Latency is expected to be in the
neighborhood of 100 ms. The media format will be similar to Xbox, with
approximately 6 GB of usable space on the disk. As on Xbox, media will
be stored on a single side in two 3 GB layers.
Industrial Design
The Xenon industrial design process is well under way, but the final
look of the box has not been determined. The Xenon console will be
smaller than the Xbox console.
The standard Xenon controller will have a look and feel similar to the
Xbox controller. The primary changes are the removal of the Black and
White buttons and the addition of shoulder buttons. The triggers,
thumbsticks, D-pad, and primary buttons are essentially unchanged. The
controller will support vibration.
Xenon Development Kit
The Xenon development environment follows the same model as for Xbox.
Game development occurs on the PC. The resulting executable image is
loaded by the Xenon development kit and remotely debugged on the PC.
MS® Visual Studio® version 7.1 continues as the development
environment for Xenon.
The Xenon compiler is based on a custom PowerPC back end and the
latest MS® Visual C++® front end. The back end uses technology
developed at MS for Windows NT on PowerPC. The Xenon software group
includes a dedicated team of compiler engineers updating the compiler
to support Xenon-specific CPU extensions. This team is also heavily
focused on optimization work.
The Xenon development kit will include accurate DVD emulation
technology to allow developers to very precisely gauge the effects of
the retail console disc drive.
Miscellaneous Xenon Hardware Notes
Some additional notes:
•Xenon is a big-endian system. Both the CPU and GPU process memory in
big-endian mode. Games ported from little-endian systems such as the
Xbox or PC need to account for this in their game asset pipeline.
•Tapping into the power of the CPU is a daunting task. Writing
multithreaded game engines is not trivial. Xenon system software is
designed to take advantage of this processing power wherever possible.
The Xbox Advanced Technology Group (ATG) is also exploring a variety
of techniques for offloading graphics work to the CPU.
•People often ask if Xenon can be backward compatible with Xbox.
Although the architecture of the two consoles is quite different,
Xenon has the processing power to emulate Xbox. Whether Xenon will be
backward compatible involves a variety of factors, not the least of
which is the massive development and testing effort required to allow
Xbox games run on Xenon.