In the test 15 years ago: Microsoft WHQL torpedoed Nvidia's Quad-SLI

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With the GeForce 7900 GX2 and 7950 GX2, Nvidia already offered dual GPU graphics cards in July 2006. The ForceWare 91.37 was the first graphics driver to support Quad-SLI. In the test 15 years ago, two GeForce 7950 GX2 (test) competed. In terms of performance, Microsoft Nvidia thwarted the bill.

Table of contents

  1. 1 Two GeForce 7950 GX2 = four G71 GPUs
  2. SLI modes: AFR, SFR or AFR of SFR
  3. It looked bleak in the benchmarks
  4. Conclusion
  5. Multi-GPU gaming PCs today

Two GeForce 7950 GX2 = four G71-GPUs

To test Quad-SLI, two GeForce 7950 GX2 from Gigabyte were used, each with two G71 GPUs. The GPUs each worked at 500 MHz, which is 150 MHz slower than a G71 on a GeForce 7900 GTX. Each of the two graphics cards had 2 × 512 MB graphics memory, whereby the effective total memory available was not 2 GB. For a Quad-SLI team, Nvidia offered four different rendering modes in the driver, which differed greatly in terms of performance and compatibility.

GeForce 7950 GX2 GeForce 7900 GTX Radeon X1900 XTX Chip 2 × G71 G71 R580 transistors approx. 2 × 278 million approx. 278 million approx. 384 million production 90 nm chip clock 500 MHz 650 MHz pixel pipelines 2 × 24 24 16 shaders Units per pipeline (MADD) 2 3 FLOPs (MADD/ADD) 2 × 192 GFLOPS 250 GFLOPS 374 GFLOPS ROPs 2 × 16 16 pixel fill rate 2 × 8,000 MPix/s 10,400 MPix/s TMUs per pixel pipeline 1 texel fill rate 2 × 12,000 MTex/s 15,600 MTex/s 10,400 MTex/s vertex shader 2 × 8 8 triangular throughput 2 × 1,000 MV/s 1,400 MV/s 1,300 MV/s pixel shader PS 3.0 vertex shader VS 3.0 memory size 2 × 512 MB GDDR3 512 MB GDDR3 memory clock 600 MHz 800 MHz 775 MHz memory interface 2 × 256 bit 256 bit memory bandwidth 2 × 38,400 MByte/s 51,200 MByte/s 49,600 MByte/s precision per channel FP16/FP32 FP32 SLI/CF support yes

SLI modes: AFR, SFR or AFR of SFR

The fastest mode was “Alternate Frame Rendering” (AFR). A complete frame was calculated here in turn by each GPU and these frames were then output. Since each GPU had to hold all the data from the game scene, the effective graphics memory for two GeForce 7950 GX2 was 512 MB. A disadvantage of AFR was that it had to be specifically incorporated into their game by game developers. If that wasn't the case, the driver switched to the second mode called “Split Frame Rendering” (SFR). A single frame was dynamically divided into several areas and each GPU worked on the area assigned to it. Then a complete frame was assembled from the parts and output. SFR typically had lower performance than AFR but was compatible with any game. As a compromise between the two solutions, Nvidia introduced AFR of SFR, a third mode specifically for quad SLI. Here, two GPUs worked on one frame and the other two GPUs worked on the next frame. The performance was placed between AFR and SFR.

Standard SLI mode 3D application 4WayAFR AFR of SFR 4WaySFR 3DMark05 – ✓ compatible Battlefield 2 – ✓ compatible Call of Duty 2 – ✓ compatible Doom 3 ✓ – compatible F.E.A.R. – ✓ compatible HL2: Lost Coast – ✓ compatible Oblivion – ✓ compatible Quake 4 ✓ – compatible Riddick ✓ – compatible Serious Sam 2 – ✓ compatible SpellForce 2 – ✓ compatible Splinter Cell 3 – ✓ compatible TR: Legend – ✓ compatible

Fifteen years ago, the question arose: if developers can use AFR, why should they switch to AFR of SFR? The answer to this was found in the Direct3D 9 standard. In order to receive WHQL certification for a graphics driver from Microsoft, the driver was only allowed to accept parameters for a maximum of three frames when rendering a frame. Since four frames were rendered in parallel with four GPUs in AFR mode, this procedure would have resulted in the driver being denied WHQL certification. This problem has been circumvented with AFR of SFR. It looked different in OpenGL titles: Here the driver could use AFR with four GPUs, if supported by the developers.

In The benchmarks looked bleak

Due to the problem described, it did not look good in the benchmarks for the Quad-SLI team. In 1,280 × 1,024 pixels, the quad SLI system had a lead of only 14 percent over a single GeForce 7950 GX2, and thus less than the 20 percent that two GeForce 7900 GTX worked faster. In 1,600 × 1,200 pixels, the lead grew to 22 percent – and thus 1 percent more than with two GeForce 7900 GTX. As was to be expected, the Quad-SLI team made the most sense in resolutions that were extremely high for the time, such as 2,560 × 1,600 pixels. Here, the performance advantage over a GeForce 7950 GX2 was 31 percent. However, two Radeon X1900s worked another 3 percent faster.

«Previous rating SLI/CF quality 1280x1024Rating SLI/CF quality 1600x1200Performancerating XHD-GamingPerformancerating OpenGLVolume SLI/CFTemperature SLI/CFPower consumption SLI/CF Next»

In order to see the full potential of the four GPUs, the increase in performance in OpenGL titles with AFR support could be examined. The two GeForce 7950 GX2 were able to take the lead without any problems – the performance compared to a GX2 increased by 78 percent and compared to two GeForce 7900 GTX by 35 percent.

The Quad SLI system could not convince in the B grades. The noise level doubled, the GPU temperatures under load were over 100 ° C and the energy consumption of the entire system increased by almost 50 percent under load. Not to mention micro stutters, which were not an issue at the time.

Conclusion

Quad-SLI could not convince in the test 15 years ago. The lion's share of the games relied on the Direct3D API and was therefore unable to use AFR in combination with four GPUs. The increase in performance was therefore in no way appropriate to the additional costs. In addition, a system with four GPUs ensured hotter and louder graphics cards and higher energy consumption. For the few people who absolutely wanted to use four GPUs, Nvidia at least offered the option.

Multi-GPU gaming PCs today

Multi-GPU systems play a subordinate role these days. The GeForce RTX 3000 series no longer supports SLI at all, only DirectX 12 and Vulkan titles can implement multi-GPU support themselves. The result is practically not worth the effort to any developer. Numerous problems with SLI such as micro-stuttering, high acquisition and maintenance costs as well as low performance gains made the technology increasingly unattractive. At the end of 2020, only 1 percent of ComputerBase readers said they owned a multi-GPU system.

Do you use multi-GPU technology ?

  • Yes, Nvidia SLI – 1.6%, 0.9%, 0.9% 0.7%
  • Yes, AMD Crossfire – 0.7%, 0.5%, 0.3% 0.3%
  • No – 97.7% , 98.6%, 98.8% 99.1%

7,063 participants & nbsp; • & nbsp; Final result

In the “Tested 15 years ago” category, the editorial team has been looking into the test archive every Saturday since July 2017. The last 20 articles that appeared in this series are listed below:

  • An overclocked GeForce 7600 GS with 512 MByte memory
  • Intel's Core 2 Duo E6600 and E6700 cleaned up with AMD
  • The absolute price-performance tip GeForce 7600 GST
  • The Core 2 Extreme X6800 left everyone behind
  • The Zalman VF-900 Cu dominated them all
  • Three GeForce 7950 GX2 from loud to fast
  • GeForce custom designs in extra fast and silent
  • The “gamer cube” that only ventilated via the power supply

    • < li> Nvidia's double-decker alias GeForce 7950 GX2

  • Intel's Core 2 Duo E6700 shone in the preliminary test
  • Nvidia's nForce 500 for AMD's AM2 socket with DDR2 RAM
  • The best The Radeon X1900 XTX came with a Zalman cooler
  • PCIe x8 versus PCIe x16 for multi-GPU systems
  • ATi's X1900 GT bit its teeth against Nvidia's 7900 GT

    • < li> PhysX accelerator for 299 euros from Ageia

  • The GeForce 7600 GS was a stunner for 125 euros
  • HTPC case from Lian Li and Silverstone
  • Die GeForce 7900 GTX in 90 nm and with a higher clock rate
  • Creative Sound Blaster X-Fi for more audio quality and FPS
  • Intel's Pentium EE 965 was faster and more economical

Even more content of this kind and many more reports and anecdotes can be found in the retro corner of the ComputerBa forum se.