Review
ATi Radeon X800 XT PCIe
by
John
Reynolds
Introduction
The
old adage, if its not broke, dont fix it,
comes to mind with ATi's Radeon X800 graphics boards.
When ATi released the 9700 Pro in the fall of 2002
using a 150nm process, the world-and more importantly for
the company, their competition was taken by surprise.
The R300 architecture, upon which the 9700 Pro was based,
was a DX9 compliant part that used floating point precision
throughout its rendering pipelines, a design that wasnt
thought possible by most of the industry if using the older
fabrication process. Yet this is exactly what ATi accomplished,
introducing the first DX9 graphics chip months ahead of competing
parts, and moreover outperforming the competition once it
arrived significantly later. In fact, ATi obviously felt so
confidant in their new architecture that they have continued
to essentially leave the core technology unchanged for several
refreshes throughout 2003 and for this years new generation,
the X800 series of products. This has allowed ATi to instead
focus engineering resources on a new architecture that will
be powering both Microsofts Xbox 2 console and the companys
next generation of graphics boards for the PC.
Announced
this past May, the Radeon X800 product series consists of
the X800 Pro, the X800 XT, and the X800 XT
PE (Platinum Edition). Based on the R420 architecture
(R423 for PCIe versions), these chips are 160m transistor
parts manufactured using TSMCs 130nm low-k process and
have a 256-bit memory interface that supports DDR, GDDR2,
and GDDR3. To diversify the X800 product line so that it can
address multiple price points in the market, ATi has created
the following board specifications:
|
X800 Pro
|
X800 XT
|
X800 XT PE
|
Pipelines |
12 pipes
|
16 pipes
|
16 pipes
|
Clock speed |
475 MHz
|
500 MHz
|
520 MHz
|
Pixel Fill-rate |
5.7 GP
|
8 GP
|
8.3 GP
|
Memory speed |
450 MHz
|
500 MHz
|
575 MHz
|
Memory bandwidth |
28.8 GB
|
32 GB
|
36.8 GB
|
MSRP |
$400
|
$450
|
$500
|
The R300 was the first graphics
chip on the market to feature eight pixel pipelines, and ATi
has continued this parallelism by doubling the number of pipes
for the R420 and increasing the vertex engine from four to
six units. Yet while there are chip and memory speed variations
among the X800 lineup, the most noteworthy difference is the
X800 Pros 12 pipelines as opposed to the other boards
16 pipes. Essentially the same chip as the XT and XT PE but
with one block, or quad, of pipelines disabled, the Pros
configuration results in a significantly lower fill-rate.
The boards themselves offer ATi's typical output options,
with single VGA and DVI connections and an S-video port. And
thanks to the use of TSMCs low-k process, the X800s
are single slot boards that can be installed in small form
factor PCs and cooled using a copper heatsink and fairly quiet
fan (the speed for which is controlled by an on-die thermal
probe that monitors the chips temperature and adjusts
its rotation accordingly). In fact, the 256 MB of GDDR3 memory
that ATi uses for these new cards does not require active
cooling, so the heatsink doesnt actually make contact
with the RAM modules (four on the front and back each) on
the board.
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X800 Architecture Overview
As mentioned above, the Radeon
X800 XT is a 16 pipeline configuration that also includes
six vertex units, identical to the GeForce 6800 GT PCIe
board SimHQ reviewed
earlier this year. The following is a list of the features
the X800 boards support:
Smartshader
HD
- Support for DirectX 9.0 programmable
vertex and pixel shaders in hardware
- DirectX 9.0 Vertex Shaders
- Vertex programs up to 65,280 instructions
with flow control
- Single cycle trigonometric operations
(SIN & COS)
- DirectX 9.0 Extended Pixel Shaders
- Up to 1,536 instructions and 16
textures per rendering pass
- 2nd generation F-buffer technology
accelerates multi-pass pixel shader programs with unlimited
instructions
- 32 temporary and constant registers
- Facing register for two-sided lighting
- 128-bit, 64-bit & 32-bit per
pixel floating point color formats
- Multiple Render Target (MRT) support
- Complete feature set also supported
in OpenGL via extensions
Smoothvision HD
- 2x / 4x / 6x Anti-Aliasing modes
- Sparse multi-sample algorithm with
gamma correction, programmable sample patterns, and centroid
sampling
- Lossless Color Compression (up
to 6:1) at all resolutions
- Temporal Anti-Aliasing
- 2x/4x/8x/16x Anisotropic Filtering
modes
- Up to 128-tap texture filtering
- Adaptive algorithm
3Dc
- High quality 4:1 Normal Map Compression
- Works with any two-channel data
format
Hyper Z HD
- 3-level Hierarchical Z-Buffer with
Early Z Test
- Lossless Z-Buffer Compression (up
to 48:1)
- Fast Z-Buffer Clear
- Z Cache optimized for real-time
shadow rendering
Videoshader HD
- FULLSTREAM technology for Real,
DivX, and WMV9 formats
- All-format DTV/HDTV decoding
- Adaptive Per-Pixel De-Interlacing
and Frame Rate Conversion (temporal filtering)
Display Features
- Dual integrated 10 bit per channel
400 MHz DACs
- Integrated 165 MHz TMDS transmitter
(DVI 1.0 / HDMI compliant and HDCP ready)
- Integrated TV Output support up
to 1024x768 resolution
- YPrPb component output for direct
drive of HDTV displays
While the pixel shader architecture
of the R420 is nearly identical to that of the R300, the newer
chip has been modified to make improvements in its rendering
capabilities. The number of registers and instruction limits
have both been increased, which should help performance and
prevent developers from running into issues with instruction
lengths while developing current and near-future engines.
The X800s are, however, are still Shader Model 2.0 parts and,
as such, do not support features like dynamic branching and
flow control, though its worth noting that such features
are used to aid performance and not create visual effects
otherwise impossible to render without SM 3.0 support. And
as with the R300 architecture, the X800s use 24-bit floating
point precision throughout their rendering pipelines.
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One
new feature found in the X800 parts that ATi has been heavily
touting is 3Dc, a compression tool for normal maps. As game
developers strive to create more detailed and realistic looking
environments, one of the key means of doing so has traditionally
been through higher levels of geometry for game models and
environments . However, even greater levels of geometry with
multiple texture layers applied can still appear as rather
flat and unrealistic looking, and the level of geometry required
to avoid this appearance would be beyond the means of graphics
boards engineered for the consumer market, which have traditionally
been designed with more of an emphasis on pixel rather than
geometry rendering (in contrast to professional graphics workstations).
Because of this situation, developers have begun relying on
a technique known as normal mapping, which is a special texture
map that stores information dealing with how in-game light
interacts with the rendered surface. This creates an illusion
of greater detail than whats actually present while
taking advantage of consumer graphics boards emphasis
on pixel processing.
However,
for a normal map to create a model or object that is substantially
more realistic looking than traditional rendering techniques,
the level of geometry and texture detail required to generate
the normal map increases the memory space requirements to
load the map into a graphics boards frame buffer, which
is obviously finite in space and required for other uses.
3Dc, a 4:1 compression algorithm for normal maps thats
based on DX5s texture compression mode (DXTC), is what
ATi hopes will enable developers to make greater use of normal
mapping by allowing them to create either more detailed normal
maps or to use the feature to save memory space and bandwidth
by applying it to non-compressed normal maps. In fact, according
to ATi numerous game developers have indicated that they plan
to include 3Dc support in future games.
Test System Setup
- Intel Pentium 4 Extreme Edition
3.4 GHz
- Intel D925XCV (925X chipset) motherboard
- 1 GB (2x512 MB) Micron DDR2 533
MHz RAM
- ATi Radeon X800 XT PCIe 256MB (Catalyst
4.10)
- Maxtor MaXLine III (16 MB buffer)
native SATA HD
- Windows XP Professional (SP2)
- DirectX 9.0c
The benchmark suite that will be used
to evaluate this test system is listed here.
Again, unless specified otherwise all games are configured
to their highest settings, and 32-bit color and trilinear
texture filtering are the default baseline during testing.
Also, Windows XP is configured to have Automatic Update,
System Restore, and all unnecessary startup services disabled.
Fraps 2.3.2 is used to record performance scores unless otherwise
noted.
In
addition, along with the latest Catalyst driver release from
ATi the Catalyst Control Center (CCC), the new .NET Framework-based
replacement for the traditional control panel, was also installed
and used to disable ATi's new A.I. optimizations throughout
testing. The X800 series of graphics chips use a more aggressive
filtering method than their predecessors, and the Catalyst
driver suite now includes title-specific optimizations and
shader replacements, all of which are of course intended to
accelerate performance in targeted games. In all fairness,
however, some of the application detections are designed to
avoid known bugs or issues, such as disabling anti-aliasing
for the Splinter Cell titles since the feature is incompatible
with these games. Either way, ATi allows the end user to toggle
A.I. settings via the CCC and care was taken to ensure that
A.I. was disabled throughout testing.
The X800 XT reviewed today is a native
PCI Express board that can take advantage of the full up-
and downstream bandwidth of the new bus. It draws power from
the test systems PSU via a 6-pin connector on the back
of the board.
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Benchmark
Scores
The test option of High Quality represents
scores with both 4x AA and 8x AF enabled.
Lock
On: Modern Air Combat was tested using the MiG-29 Intercept
demo. In-game settings were at their highest options, except
for several features such as water and heat bltr which were
set to low and turned off. The demo was run for three minutes
and scores were recorded using Fraps.
LOMAC scales well with graphics
options and resolution changes, displaying a roughly 20% frame
rate loss from 4x AA and slightly over 30% for 8x AF; neither
feature allows for playable frame rates at 1600x1200 however.
With both features combined, the simulation is barely playable
at 1024x768.
Microsofts Flight
Simulator 2004 was tested using SimHQs in-house
dusk flight over the city of Hong Kong, with an external camera
view set behind the plane. Frame rate recording is stopped
once the plane lands. MS2004 was configured with ultra
high settings across its four hardware panels.
Another simulation that scales with
changes to the graphics sub-system, FS2004 incurs a
much sharper performance hit from anisotropic filtering than
from anti-aliasing in SimHQs test flight video. 4x AA
drops the frame rate by 20-30% across the tested resolutions,
while 8x AF performance is closer to 40-50% lower than the
baseline scores. And High quality isnt a viable option
at any of the tested resolutions with the titles in-game
options configured with ultra high settings, except for perhaps
1024x768.
IL-2:
Forgotten Battles - Aces Expansion Pack represents
SimHQs non-modern flight simulation test. Using OpenGL,
the landscape option was set to perfect and all other graphics
options were at their highest settings. Testing consisted
of using the Black Death track.
IL2: FB AEP takes the least
performance hit from anti-aliasing among the flight simulations
tested for this review, losing less than 10% at 1024x768,
roughly 15% at 1280x960, and increasing to almost 20% at 1600x1200.
As in the past, the simulation incurs a much sharper loss
from anisotropic filtering, with frame rates dropping by around
30-50% across the resolutions and leaving the game unplayable
at 1600x1200. And as with the above titles, high quality isnt
a viable option at the higher resolutions.
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Far
Cry benchmark numbers are generated by repeated playing
of the Research map, which consists of an good mix of beach,
jungle, and interior settings found throughout the games
various levels. Fraps is used to record performance as the
same path is taken through the map during each test. Both
anti-aliasing and anisotropic filtering were enabled via the
Catalyst Control Center and all in-game options were configured
for their highest settings (water at ultra high).
Far Cry is the most graphically
demanding game in SimHQs benchmark suite, and is the
only title tested that makes use of DX9 shaders. As such,
it certainly allows the X800 XT to shine, as the above scores
indicate, pushing into 3-digit frame rates at 1024x768. With
anti-aliasing enabled, the performance loss scales from roughly
15-30%, while anisotropic filtering is even lower, roughly
5-15%. Even high quality offers playable frame rates at 1600x1200,
at which point the game is rendering some of the best visuals
currently available for PC gaming.
Developed using id Softwares
five-year-old Quake 3 engine, Call
of Duty is the second title SimHQ uses testing OpenGL
rather than the D3D API. Scores were derived from the Dawnville
demo using the in-game timedemo utility to capture performance.
The com_maxfps console command was also used to
lift the default frame rate cap of 85.
Based on an aging engine, Call
of Duty isnt particularly graphics intensive, though
the title still looks good once AA and AF are enabled. Both
features incur very similar performance losses, and the game
stays in the realm of triple digit frame rates even at 1600x1200
with high quality settings.
NASCAR
Racing 2003 Season was tested using SimHQs in-house
replay, which consists of a crowded Daytona track with the
camera view set to Earnhardts cockpit. All graphics
options were placed at their highest settings.
This driving simulation obviously
scales far closer to system rather than graphics processing
power, essentially locking itself at 35-38 fps across all
tested resolutions and settings. And with shadows enabled,
NASCAR performs much slower in these tests compared to scores
from SimHQs CPU articles which test without shadows.
Last, SimHQ has decided to include
scores from Valves Video
Stress Test, a utility now included with the new Source
engine-based version of Counter-Strike. The update
of the popular online shooter is currently available only
via Valves distribution package, Steam, but will be
bundled with Half Life 2 once the game reaches store
shelves. The Video Stress test itself is a fly-by of a relatively
small custom level and is designed to show off numerous graphical
effects rendered through the heavy use of various shaders.
Its interesting to note that
the Video Stress test loses more performance from the fill-rate
demands of higher resolutions than it does from either AA
or AF. Anti-aliasing costs the test slightly more at higher
resolutions than anisotropic filtering, roughly 5-20% across
the resolutions. At high quality the frame rate is cut by
some 45% across the resolutions, though if the test represents
a games final performance based on the Source engine,
74 fps at 1600x1200 with 4x AA and 8x AF is hardly a negligible
score.
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Image Quality
ATi's GPUs have since the 9700
Pro supported programmable multi-sampling modes of anti-aliasing.
In addition, the X800 does not possess a hardware ROP (render
output) limitation, allowing for more than four sub-samples
to be used. While the AA modes are programmable, when enabled
via the control panel a static, sparse sampling pattern is
used, and to which ATi applies a gamma correction that gives
the X800s AA a slight quality advantage with thin lines
or along edges with a sharp color contrast. And while the
X800 is capable of supporting super-sampling, ATi has chosen
to not expose this mode of anti-aliasing for their products.
Regardless, using Colourless D3D FSAA viewer the sparse
sampling pattern of the X800s can be seen below:
4x AA Sampling Pattern
6x AA Sampling Pattern
A newly introduced feature for ATi's
GPUs this year is temporal AA. As with A.I., temporal anti-aliasing
can only be enabled using ATi's CCC and not the companys
older control panel. Temporal AA is a feature that takes advantage
of the programmable sampling patterns available in ATi hardware
since the R300. By changing the sampling pattern used per
frame, temporal AA increases the visual quality of the AA
mode enabled to an appreciable degree. The caveat with the
feature, however, is that frame rate must stay high or the
changing sampling patterns will become apparent to the human
eye, resulting in a flickering along polygon edges that detracts
from the AA quality. Enabling temporal AA, however, also enables
V-Sync. The performance of the various anti-aliasing modes
were tested using IL2: FB AEP's "Black Death"
track.
As we can see above, 6x AA obviously
incurs a higher performance impact than 4x AA, though IL-2
remains fairly playable even at 1600x1200 and certainly looks
amazing. Temporal AA, however, is really only useful for
IL-2 when configured with maximum settings at the lower
resolutions, since the lower frame rate will result in the
shifting patterns becoming noticeable. Again, because V-sync
is enabled with temporal AA, its scores are lower than the
other 4x AA numbers since the frame rate is unable to go above
the refresh rate; otherwise, temporal AA has no impact beyond
regular AA modes. Visually, however, for games that can maintain
high frame rates, temporal AA significantly increases the
anti-aliasing quality and really has to be experienced hands-on
to be truly appreciated.
According to ATi, A.I. examines a
games textures as theyre loaded and, using an
adaptive filtering algorithm, evaluates how to best filter
them from a performance perspective without causing a noticeable
degradation in filtering quality. The setting of low for A.I.
enables all title-specific optimizations and the adaptive
filtering algorithm, while the high setting also enables the
optimizations as it increases the aggressiveness of the filtering
algorithm. The filtering differences can be seen in these
images, created using the Direct3D AF Tester utility:
Direct3D Anisotropic
Filtering (AF) Test Results
|
|
Optimizations Off |
Optimizations On |
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IL-2: Forgotten Battles - Aces
Expansion Pack was used to test the performance impact
A.I. has on texture filtering with 8x anisotropic enabled.
Image quality differences with A.I.
disabled or set at low are extremely difficult to discern,
with a slight increase in texture aliasing in certain titles
being the most noticeable effect. Once set to high, however,
the more aggressive filtering algorithm results in a perceptible
banding in textures that would be expected when bilinear filtering
was in use, though not quite as apparent as true bilinear.
And as the scores above demonstrate, A.I. has a strong impact
on performance, with the setting low increasing test scores
by 30-50% over regular 8x AF and high returning the frame
rate to numbers almost identical to those without anisotropic
filtering enabled. Those desiring the best image quality possible
for their games, however, will want to leave A.I. either turned
off or set at low, though ATi should be congratulated for
allowing users the choice through the CCC.
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Overclocking
To see how well the Radeon X800
XT would run above its default clock settings for both
the chip and onboard memory, the Catalyst Control Centers
Overdrive option was enabled and IL2: FB AEP again
ran through a variety of tests. SimHQ, however, strongly stresses
that the overclocking results of one review board cannot serve
as an adequate sampling by which to judge an entire product
line, and for our readers to please keep this in mind while
considering the following benchmarks.
With Overdrive enabled the chip clock
speed was increased to a paltry 506 MHz while the memory maintained
its default of 500 MHz. With the Platinum Editions clocked
a mere 20 MHz faster than the XTs, its no surprise that
500+ MHz appears to be the threshold for these chips. As for
the memory, the Samsung modules are rated at 2ns and a frequency
of 500 MHz, so its unsurprising that the onboard RAM
would overclock poorly, if at all.
Gallery
All pictures were taken at 1024x768
using 4x anti-aliasing and 8x anisotropic filtering.
|
|
Far Cry |
NASCAR Racing 2003 Season |
|
|
Rome: Total War |
3Dc |
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Conclusion
It appears as though ATi's confidence
in the core architecture the company released with the Radeon
9700 Pro back in 2002 is a gamble that hasnt yet
backfired. The X800 series of boards has won numerous OEM
contracts and been extremely popular with gamers in the retail
market, though availability for the XT and PE boards has been
poor throughout the summer. The Radeon X800 XT used
in this review displayed no issues rendering any of the games
in the benchmark suite, nor were there any stability problems
with the test system while running the board. And the new
Catalyst Control Center is a fairly user friendly control
panel that offers a wide host of configurable options for
the end user, though in its current form it is somewhat bloated
in terms of system resources required to run; hopefully ATi
will be able to optimize the package in the near future.
Though we suspect the Radeon X800
XTs performance is somewhat limited by the 500 MHz
GDDR3 memory installed, the board still managed to blaze through
many of the games included in SimHQs benchmark suite.
This hardly comes as a surprise, considering the sheer fill-rate
generated by 16 pixel pipelines running at 500 MHz, a high
frequency achieved largely due to TSMCs 130nm low-k
process and ATi's choice of employing it for this generation
of high-end chips. While the R420 design lacks support for
certain features found in Shader Model 3.0, and for higher
floating point precision rendering, its doubtful a game
will be released within an expected lifespan for the X800
boards that significantly eclipses their capabilities. And
unique features such as temporal anti-aliasing and 3Dc are
worth consideration for those looking to purchase a high-end
graphics card. ATi has struck a remarkable balance over the
past few generations, successfully leveraging their initial
DX9 architecture across several years, largely through the
smart use of process technology, while freeing up the engineering
resources necessary to work on a future design that has already
won one major contract: Microsofts upcoming Xbox
2 console. Only time will tell, however, whether or not
ATi's future design will likewise function as an architectural
vinculum, a foundation able to bridge generations of products
as the graphics industry transitions itself toward Longhorn
and DirectX 10.
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