32 MA XIMUMPC NOVEMBER 2005
NVIDIA’S SLI VS.
ATI’S CROSSFIRE
When nVidia announced its Scalable Link
Interface (SLI) technology in September
2004, industry observers knew ATI would
have to respond with a dual-GPU technol-
ogy of its own. ATI fi nally did, announcing
CrossFire in May 2005. As we were going to
press in mid-August, however, ATI informed
us that the X850 XT CrossFire Edition wasstill “in the fi nal stages of qualifi ca-
tion” and that we wouldn’t receive
evaluation hardware by our deadline.
In any event, here’s what we know
about SLI and CrossFire to date.NVIDIA SLI
nVidia’s SLI solution requires a motherboard
with an nVidia nForce4 chipset, two x8 or
x16 PCI Express expansion slots, and a
proprietary SLI connector board that bridges
two matching GeForce videocards.
The two cards must sport the exact
same GPU—you can’t pair a 6800 Ultra card
with a 7800 GTX, for instance. What’s more,
both cards must also be from the same man-
ufacturer—a situation that nVidia intends to
change with its ForceWare 80 driver update.
The two cards maintain separate frame buf-
fers, but output to a single monitor.
As you can see from the benchmark
numbers on page 30, SLI delivers a substan-
tial increase in performance—but we’ve
yet to see the “up to 2x” leap in per-
formance that nVidia touts.ATI CROSSFIRE
Not to beat a dead horse, but every-
thing we can report about ATI’s dual-
GPU solution is old news—except pricing.
CrossFire will require a motherboard
with an ATI CrossFire chipset and two PCIExpress expansion slots. ATI has
announced three CrossFire Edition video-
cards: Two are based on 16-pipe GPUs (the
$300 X800 XL and the $350 X850 XT) and
are outfi tted with 256MB each. The third
card is based on ATI’s eight-pipe X800 GPU
and comes with 128MB of memory. It will
be priced at $200.
CrossFire Edition cards can operate
on their own or be paired with any sec-
ond videocard based on the same GPU
series. You can link an X800 XL CrossFire
Edition card, for instance, to any manu-
facturers’ X800, X800 GT, or X800 XL
product. But there’s a catch: The system
will achieve parity by resorting to the
lowest common denominator in terms of
pixel pipelines and frame buffer. Harness
a 16-pipe X800 XL CrossFire Edition to a
12-pipe X800 Pro, for instance, and the
CrossFire board will shut down four of its
pixel pipelines.OUR TOP VIDEOCARD PICKS
ATI has had more than its fair share of missteps so far this year, but
the company’s lower-priced Radeon GPUs helped ATI and its partners
win at least the fi rst two matches in this series of championship bouts.
But each of those wins comes with two major caveats: The fi rst—that
nVidia has a dual-GPU solution, and ATI doesn’t—could become a
moot point if ATI manages to ship CrossFire and it works as prom-
ised. The second—ATI’s across-the-board poor showing in our video
benchmarks—isn’t so easy to overcome.
In the lightweight class, Sapphire’s Radeon X800 GT won by
a knockout, thanks to superior benchmark numbers and the fact
that it has twice the memory of Leadtek’s GeForce 6600 GT board.
Connect3D’s 16-pipe 3028 X800XL fl oated like a butterfl y and stung
like a bee as it took the welterweight class; it had MSI’s 12-pipeNX6800 card up against the ropes as soon as it stepped into the ring.
We generally prefer performance over price, but XFX’s GeForce
6800GT won the middleweight championship on points—100 points,
to be exact: The card was selling for a hundred bucks less than
Sapphire’s only slightly faster Radeon X850 XT.
In hindsight, pitting ATI’s top-of-the-line X850 XT Platinum Edition
against nVidia’s second-string GeForce 7800 GT was like putting the
Maytag Repairman in the ring to face Mike Tyson; but hey, that was
the best GPU ATI had to offer. Needless to say, BFG’s GeForce 7800
GT OC won the heavyweight bout.
When the time came for the super-heavyweight match, we had
no choice but to pit two cards powered by nVidia’s top-of-the-line
GeForce 7800 GTX against each other. PNY’s Verto is an excellent
value at $520, but Asus’ Extreme N7800 for $580 is the card we’d
take into a dark alley.ATI’S NEXT-GENERATION GPU
If you think ATI is uptight about revealing new information about
CrossFire, try asking about its much-delayed next-generation graphics
core, code-named R520. Industry analysts expected to see this chip
by the summer of 2005, but board manufacturers we spoke with in
late-August said ATI told them not to expect even samples until mid-
October—nearly six months after cards based on nVidia’s own next-gen part were already on store shelves.
Our sources tell us the as-yet-unnamed chip will feature a 90-
nanometer process, that it will (fi nally) support Shader Model 3.0,
and that it will boast a 512-bit memory interface. Sources also tell us
R520-based cards will be available in four confi gurations: the R
XT and R520 XT CrossFire Edition (both of which will require a dual-
slot cooler), and the R520 XL and R520 Pro (both of which will use a
single-slot cooler).still “in the fi nal stages of qualifi ca-
tion” and that we wouldn’t receive
evaluation hardware by our deadline.
In any event, here’s what we know
about SLI and CrossFire to date.nVidia’s SLI solution requires a motherboard
with an nVidia nForce4 chipset, two x8 or
x16 PCI Express expansion slots, and a
proprietary SLI connector board that bridges
two matching GeForce videocards.
The two cards must sport the exact
same GPU—you can’t pair a 6800 Ultra cardExpress expansion slots. ATI has
announced three CrossFire Edition video-
cards: Two are based on 16-pipe GPUs (the
$300 X800 XL and the $350 X850 XT) andpress in mid-August, however, ATI informed
us that the X850 XT CrossFire Edition wasboth cards must also be from the same man-
ufacturer—a situation that nVidia intends to
change with its ForceWare 80 driver update.
The two cards maintain separate frame buf-
fers, but output to a single monitor.
As you can see from the benchmark
numbers on page 30, SLI delivers a substan-
tial increase in performance—but we’ve
yet to see the “up to 2x” leap in per-
formance that nVidia touts.ATI CROSSFIRE
Not to beat a dead horse, but every-
thing we can report about ATI’s dual-
GPU solution is old news—except pricing.
CrossFire will require a motherboard
with an ATI CrossFire chipset and two PCIATI’S NEXT-GENERATION GPU
VIDEOCARD SHOWDOWN
nVidia’s
dual-card
SLI
ATI’s
dual-card
CrossFire