TABLE OF CONTENTS
Have you heard of computer (or hardware) sandwiches? They are essentially the same as usual sandwiches in the kitchen: two pieces of PCB with something in between.
Experienced readers and seasoned users of 3D accelerators will certainly recall the memorable Quantum3D Obsidian X-24 that united two Voodoo2 accelerators in SLI mode.
This monster, born back in 1998, used to have 24MB of on-board memory (inconceivable memory volume for those times!) But this memory was rigidly divided and shared, because even the GPU was implemented with three chips (a raster unit and two texturing units per each Voodoo2). This card was more expensive than what we are promised for the dual-processor monster with 1GB of memory and 48 texturing units in total.
So, eight years after Obsidian and almost six years after 3dfx had disappeared inside NVIDIA we can see that the Moor is doing his duty even now (I mean 3dfx). The SLI project has been changed, developed, and is flourishing. For some strange reason, NVIDIA did not call the 7950GX2 card GeForce Voodoo 7900 SLI or just Voodoo 7900 SLI, even though it possesses these trademarks. We already saw stand-alone accelerators that could be united into SLI (GeForce 6600LE cards or higher), now these cards are merged into a single whole.
Indeed, the card is detected as two cards, so what? ATI cards have been detected as two devices in Windows for a long time already (since RADEON 9000). But in this case a card is divided by its video output to a monitor or TV. In return, we get guaranteed SLI in a single card. Even if a wide one. In fact, it's no wider than a regular 7900GTX with a two-slot cooler.
Ok, let's start the ball rolling. The first 7950GX2 card that has found its way to our testlab is a card from BFG. This company, unknown to most Russian users, was founded by three former employees of VisionTek that hadn't withstood competition and died. So we can say that BFG is an heir to VisionTek. Consequently, it's also oriented to the American market. To be more exact, used to be oriented. The US market is having big problems with salability of new computers and their components. The market is stagnating, there are signs of contraction due to goods glut. That's why nearly all American companies, that used to arrogantly ignore European traders, are actively seeking ways to the European and Asian markets now. Certainly, the Russian market has also become interesting to them, as one of the most dynamically growing ones. Of course, that's become possible thanks to the efforts of local marketing specialists. They bravely thrived for American attention and wanted to open their eyes. Then such grands as eVGA, BFG would say "Wow, the world is bigger than we thought!" and would start working in Russia. Of course, our most active players (ASUS, MSI, Gigabyte, etc) do not welcome such innovations. The competition is going to be severe. It's too early to say whether the Americans will succeed here. But the attempt itself to animate the market and offer new products to customers is commendable. Let the titans fight raising or dropping prices, it's up to them to decide. Users will get a wider range of products to choose from.
Now about BFG. As I have already mentioned above, it's an American company. What concerns Hi-End, it's no different from other NVIDIA partners - that is it buys boards from NVIDIA and produces the same reference cards. Two factors play a special role: Factor One - BFG thoroughly checks all cards, irregardless of where they are manufactured: whether they come from BFG plants or bought as ОЕМ. That's a new fashion, because reference cards bought from NVIDIA are usually sold without any tests - NVIDIA offers warranties anyway. Factor Two: package contents. The bundle is very unusual. But it will be described below.
So, GeForce 7950 GX2. It's two GeForce 7900 GTX chips operating at reduced frequencies in SLI mode on a single card. That is two G71 accelerators operate in a single slot. The photos above show the 7950 card in the exploded form (each part of the "sandwich" plus an adapter) as well as assembled with a cooler.
The price of compact dimensions (compared to two 7900 GTX cards) is reduced operating frequencies. Memory frequencies in the first place, as it's impossible to arrange the chips in a semicircle around the core. So the chips will be at different distances from the GPU, which implies some limitations. We can see that the 1.4ns memory (nominal 700 MHz) operates just at 600 MHz (safety margin, lower power consumption and consequently lower heat release.)
Two components are responsible for SLI: a chip on the second PCB (the one with a PCI-E connector - a lower card on the photo below), which is just a modified HSI (PCIE-to-PCIE),
and an adapter, which is inserted into special connectors on both parts of our sandwich:
As a result, we got a compact solution.
But engineers had to use very thin coolers, which limited the range of core frequencies, so it was reduced from 650 MHz to 500 MHz.
As we can see, these are just ordinary cooling systems. A closed heatsink and a fan that drives the air through it. Such a form with an elongated tail is intended to cool chips of the bridge that unites both parts of the accelerator. The core touches a copper plate soldered into the heatsink. In fact, considering cooling problems, especially the insides of the 7950 card, all the heatsinks must have been made of copper. Their efficiency would have grown significantly.
Both parts of the card are equipped with identical GPUs. They must have failed the 650MHz test for 7900GT GPUs.
On the whole, this card is no longer than the 7900 GTX.
The first cards were initially much longer (they came under a different name) and were intended to work in tandem (that is in 4-GPU configuration). Of course, it was useless to launch them on the retail market, as they required special PC cases. So their design was overhauled.
So, the new 7950 card can be installed into any modern PC case (of course, it must be a full-sized PC case, not from a barebone-kit).
But this accelerator still has some installation limitations, you can read about them on the sticker on the parcel with a card.
A full list of motherboards guaranteed to support the 7950 card can be found here.
You can also download the latest BIOS version there, which fixes problems with this accelerator, if there were any.
The card has TV-Out with a unique jack. You will need a special bundled adapter to output video to a TV-set via S-Video or RCA You can read about the TV-Out in more detail here.
Analog monitors with d-Sub (VGA) interface are connected with special DVI-to-d-Sub adapters. Maximum resolutions and frequencies:
Installation and Drivers
VSync is disabled.
RivaTuner (written by A.Nikolaychuk AKA Unwinder) readings show that the card gets very hot. This cooler is evidently not efficient enough. A dual-slot solution a-la GeForce 7900GTX would be appropriate here, but unfortunately, it's too bulky. I repeat that engineers should have used copper alloy for the heatsinks.
We managed to overclock the card to 570/1380 MHz. Considering that we have the results of GeForce 7900 GTX SLI, performance of the same SLI tandem at 570/1380 MHz can be easily calculated (approximately in between 7950GX2 and 7900GTX SLI).
Test results: performance comparison
We used the following test applications:
Summary performance diagrams
Game tests that heavily load vertex shaders, mixed pixel shaders 1.1 and 2.0, active multitexturing.
Game tests that heavily load vertex shaders, pixel shaders 2.0, active multitexturing.
Splinter Cell Chaos Theory
Call Of Duty 2 DEMO
Half-Life2: ixbt01 demo
Test results: Half-Life2, ixbt01
Game tests that heavily load pixel pipelines with texturing, active operations of the stencil buffer and shader units
DOOM III High mode
Chronicles of Riddick, demo 44
Synthetic tests that heavily load shader units
3DMark06: Shader 2.0 MARKS
3DMark06: Shader 3.0 MARKS
BFG GeForce 7950 GX2 1GB PCI-E. According to our tests, it's currently the fastest single-slot accelerator. It's impossible to choose adjectives to differentiate this solution from the SLI tandem. It used to be easy: a single-card accelerator - it's clear that we speak of a video card with one GPU or even two GPUs on a single PCB. But here we have one accelerator on two PCBs.
On the other hand, telling our readers that it's a single-slot solution means misleading those who use this term for video cards, which thickness equals the distance between TWO slots, not THREE ones. But this card occupies the space between THREE slots.
Yep, the X1900 XTX card sometimes catches up and even outperforms the new model from NVIDIA. But it happens, when its performance is limited by system resources. Results are unpredictable in this case. The X1900 XT CF turned out faster, but the price for two X1900 XT (CFE) is much higher.
So, the 7950 GX2 card is certainly a king among single stand-alone accelerators. The price will be approximately $650.
I also want to note that the video card was stable, we had no gripes with it. The cooler is not noisy, it did not speed up to maximum, even though the core temperature reached 90°C and higher. Unfortunately, you cannot replace a cooler on this video card, there are no counterparts.
And finally, I want to note once again the admirable bundle.
You can find more detailed comparisons of various video cards in our 3Digest.
BFG GeForce 7950 GX2 1GB PCI-E gets the Excellent Package award (June).
Theoretical materials and reviews of video cards, which concern functional properties of the GPU ATI RADEON X800 (R420)/X850 (R480)/X700 (RV410) and NVIDIA GeForce 6800 (NV40/45)/6600 (NV43)
We express our thanks to
and Mikhail Proshletsov personally
for the provided video card
PSU for the testbed was kindly provided by HIPER
Andrey Vorobiev (firstname.lastname@example.org)
July 19, 2006
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