Nvidia GeForce 8800
The most powerful graphics processor we’ve ever tested
30 MAXIMUMPC JANUARY 2007
T
esting incrementally faster and incre-
mentally cheaper DirectX 9 video-
cards is pretty boring when you’re on
the cusp of a new product introduction
that’s going to change everything. The
last time we got excited enough to award
a new card a Kick Ass award was when
Nvidia introduced the dual-GPU 7950
GX2—nearly six months ago!
Nvidia’s GeForce 8800 GTX and
8800 GTS change all that. Each is based
on an entirely new architecture—the
fi rst from-the-ground-up redesign since
Nvidia debuted the GeForce 7800 in
November 2005—and each is designed to
deliver awesome performance with games
designed for Microsoft’s DirectX 10 and
Shader Model 4.0. These GPUs are fast.
In our benchmarks, a single GeForce 8800
GTX delivered faster performance than two
of the fastest GeForce 7900 GTX cards
running in SLI that we’ve ever tested.
This boost is a happy development.
DX10 is so different from DX9 that we had
wondered if DX10 GPUs would be fast
with DX10 games and slow to mediocre
with DX9 titles. Since the 8800 cards are
so fast with DX9 games, there’s no reason
to wait for DX10 software to move up.STREAM PROCESSORS
The single most signifi cant difference
between 8800-series GPUs and everything
that preceded them is that they’re based
on a unifi ed shader architecture. Both
GPUs boast a staggering 681 million tran-
sistors, and the GTX is outfi tted with 128
shader-processing units (Nvidia calls them
“stream processors”). The slightly less-powerful 8800 GTS has
96 stream processors. In
both situations, each shader
unit can be dynamically allocated
to execute vertex, pixel, geometry, or even
physics instructions.
Both 8800 models possess asym-
metric clocks, meaning that the stream
processors within the cores are clocked
higher than the cores themselves. Nvidia’s
7-series architecture is similar in that its
vertex-shader units are clocked higher
than its cores. The GTX’s stream proces-
sors run at 1.35GHz, while its core hums
along at 575MHz; GTS stream processors
run at 1.2GHz with a 500MHz core.
The GTX is outfi tted with 24 rasterizers
(which convert 3D information into 2D pixels)
and can output 24 pixels per clock cycle; the
GTS is equipped with 20 rasterizers and can
output 20 pixels per cycle. Both specs rep-
resent a somewhat marginal improvement
over the 16-rasterizer 7900 GTX.
After observing ATI’s troubled X1900-
series launch last year, Nvidia didn’t take
any chances with new process-size tech-
nologies: The 8800 series is fabricated
using a 90nm process. The trade-off for
Nvidia is yield: Even though these chips
are assembled on 300mm wafers, the fabs
can fi t just 80 die on each one. We expect
the company to shift to a smaller, more
effi cient process size over time.POWER REQUIREMENTS
Considering the number of transistors on
these chips, the 8800 series is remark-
ably power effi cient. Nvidia recommends
at least a 450-watt power supply for an
8800 GTX (with a 12-volt
current rating of 30 amps)
and a 400-watt minimum
PSU for the 8800 GTS
(with a 12-volt current
rating of 26 amps). You’ll
need much more than that
for an SLI rig. Nvidia’s not
talking about quad SLI;
and the company has not
made any announcements
about a dual-GPU/single-card confi guration a la the 7950 GX2.
Each GTX card needs two six-pin
power connectors because, Nvidia tells us,
the PCI Express specifi cation allows cards
to draw only 75 watts through their edge
connector and 75 watts through each six-
pin power connector (the 8800 GTX draws
165 watts from the power supply).
Whether you’ll have enough room inside
your case for these cards is a whole other
kettle of pixels. Thanks to their thick cool-
ers, both cards consume two slots, and the
10.5-inch-long 8800 GTX just barely fi t in the
Cooler Master Centurion case we use for
our test bed (it wouldn’t fi t at all had Nvidia
not moved the dual power connectors from
the end of the card to the top edge).
The 8800 GTS is just slightly shorter
at nine inches. Both coolers are relatively
quiet, and both cards are outfi tted with
HDCP support for playing back copy-pro-
tected movies.MEMORABLE MEMORY
Stream Output is just one of the many cool
features in DirectX 10. It allows data to be
passed directly from the vertex or geome-
try shaders straight into memory and then
back to the top of the pipeline. Stream
output will deliver awesome particle and
physics effects, but its effectiveness will
hinge on having lots of available memory.
And Nvidia delivers: The 8800 GTX has
a 384-bit interface to 768MB of memory
clocked at 900MHz; the 8800 GTS has a
320-bit interface to 640MB of RAM run-
ning at 800MHz. Nvidia says it has no
plans to introduce reference-design cards
with 512- or 256MB of memory.
We think that’s a good idea. Game
developers tend to shoot for the lowest
common denominator, and we’d rather
see them stretch their artistic muscles
than squeeze their visions into too-small
frame buffers.Nvidia GeForce 8800
powerful 8800 GTS has
96 stream processors. In
both situations, each shader
unit can be dynamically allocated
to execute vertex, pixel, geometry, or evenNvidia’s GeForce
8800 GTX is the first GPU to
support Microsoft’s DirectX 10.GEFORCE 8800 SPEC CHART
8800 GTS 8800 GTX
NO. OF SHADER UNITS 96 128
CORE CLOCK SPEED 500MHz 575MHz
SHADER-UNIT CLOCK SPEED 1.2GHz 1.35GHz
FRAME BUFFER 640MB GDDR3 768MB GDDR
MEMORY SPEED 800MHz 900MHz
MEMORY INTERFACE 320-bit 384-bit
NO. OF RASTERIZERS 20 24NEXT-GEN GAMING