The Details Disclosed
The whole truth and nothing but the truth (as far as we know it)
BY MICHAEL BROWN
http://www.maximumpc.com | AUG 08 | MAXIMUMPC | 55
The Details Disclosed
UNVEILED: NVIDIA’S NEXT-GENNEXT-GENNEXT-GENNEXT-GEN GPU
W
atching the ongoing race
between AMD and Nvidia to
build the ultimate graphics
processor reminds us of the tale of the
tortoise and the hare. AMD has played
the hare, aggressively bounding ahead
of Nvidia in terms of process size, num-
ber of stream processors, frame buffer
size, memory interface, die size, and
even memory type. Yet Nvidia always
manages to snag the performance
crown. The GeForce 200 series is but the
latest example.
We convinced Nvidia to provide us
with an early engineering sample of its
high-end reference design (the GeForce
GTX 280), with very immature drivers,
for a first look at the GPU’s performance
potential. At the time of this writing, the
company is still a full month away from
shipping this product, and its lesser
cousin, the GeForce GTX 260, so we
won’t issue a formal verdict in this issue
(our full hands-on review should be on-
line by the time this issue reaches you).
As interesting as the benchmark
numbers are, the story behind this new
architecture is even more fascinat-
ing. We’ll give you all the juicy details,
but first, let’s explain the new naming
scheme: Nvidia has sowed a lot of brand
confusion in the recent past, especially
with the 512MB 8800 GTS. That card
was based on a completely different
GPU architecture than the 8800 GTS
models with 320MB and 640MB frame
buffers. The Green Team hopes to
change that with this generation.
The letters GTX now representNvidia’s “performance” brand, and the
three digits following those letters will
indicate the degree of performance scal-
ing: The higher the number, the more
performance you should expect. Using
260 as a starting line should give the
company plenty of headroom for future
products (as well as leave a few slots
open below for budget parts).MANUFACTURING PROCESS
AMD jumped ahead to a 55nm manu-
facturing process with the RV670 (the
foundation for the company’s flagship
Radeon HD 3870), but Nvidia stuck with
the tried-and-true 65nm process for the
GeForce 200 series. Nvidia cites the new
part’s long development cycle and sen-
sible risk management as justification.
The GTX 280 is an absolute beast
of a GPU: Packing1.4 billion transistors
(the 8800 GTX got by with a mere 681
million, and a quad-core Penryn has
820 million), it’s capable of bringing a
staggering 930 gigaFLOPs of process-
ing power to any given application (a
Radeon HD 3870 delivers 496 giga-
FLOPs, while the quad-core Penryn
musters just 96).
Considering the transistor count
and the 65nm process size, the GeForce
200 die must be absolutely huge (and
Nvidia’s manufacturing yields hid-
eously low). Although Nvidia declined
to provide numbers on either of those
fronts, those two questions will remain
academic in the absence of fresh and
considerable competition from AMD.(And for the record, all AMD would
tell us about its new part is that we can
expect it “real soon.”)PROCESSOR CORES
The GeForce GTX 280 has 240 stream pro-
cessors onboard (Nvidia has taken to calling
them “processing cores”). This being Nvidia’s
second-generation unifi ed architecture,
each core can handle vertex-shader, pixel-
shader, or geometry-shader instructions as
needed. The cores can handle other types
of highly parallel, data-intensive computa-
tions, too—including physics, a topic we’ll
explore in more depth shortly. The GeForce
GTX 260 is equipped with 192 stream
processors.
Although the GeForce 280 has nearly
twice as many stream processors as Nvidia’s
previous best GPU, it’s still 80 shy of the 320
in AMD’s Radeon HD 3870. But Nvidia’s
asymmetric clock trick, which enables its
stream processors to run at clock speeds
more than double that of the core, has so
far obliterated AMD’s numerical advantage.
In fact, a single GeForce GTX 280 proved to
be an average of 28 percent faster than the
dual-GPU Radeon HD 3870 X2 with real-
world games running on Windows XP, and
it was 24 percent faster running Vista.
We didn’t have an opportunity to
benchmark the GTX 280 in SLI mode (or the
GTX 260 at all), but a single GTX 280 beat
two GeForce 9800 GTX cards running in SLI
by a 9-percent margin, thanks in large mea-
sure to signifi cantly improved performance
with Crysis. (Turn to page 60 for complete
benchmark results.)