Card Details
First off, one feature that has been set for all cards in NVIDIA's new lineup is DirectX10 compatibility and NVIDIA's "Lumenex Engine", the latter of which is NVIDIA's name for 16x FSA, 128bit floating point HDR(High-Dynamic Range) and what they call "near perfect angle-independent AF". Don't forget also that the G84 will also be perfect for physics calculations, otherwise known as NVIDIA's Quantum Effects engine. The G84 and G86 share the unified shader core architecture introduced with the G80, which is essentially the architecture using "stream processors" that you've been reading so much about and which is one of the landmark architectural changes in the G80 GPU series.
While these are great features that have trickled down from the G80 for the new 8600 GTS XXX, some of the other differences between the G84 and G80 aren't as positive. Both the stream processors and memory bandwidth take huge hits down from the G80 architecture. In comparison with the 8800 GTS 640MB, the 8600 GTS will have 32 stream processors down from 96 and 128-bit memory buses down from 384-bit. And before you start salivating at the idea of unlocking hidden stream processors and memory bandwidth, NVIDIA confirmed that the G84 is actually a completely different GPU, not just a crippled G80, so the number of stream processors and memory support are fixed.
However, NVIDIA reference specs for the core and RAM speeds have tried to compensate for the significant reductions they've made to the architecture. But seeing that XFX has always taken things a step further with their XXX versions, the boost in speeds are very pleasing. The XXX version which we received for this article runs 730MHz core / 1130MHz (2.26GHz DDR) RAM while a stock 8600 GTS runs 675MHz core / 1000MHz (2.0GHz DDR) RAM.
Here is a detailed chart characterising the specs of the new 8600 GTS and GT.
| Spec |
GeForce 8600 GTS (NVIDIA Stock) |
XFX 8600 GTS XXX |
GeForce 8600 GT (NVIDIA Stock) |
| GPU |
G84 |
G84 |
G84 |
| Fab Process |
80nm |
80nm |
80nm |
| Transistor Count |
289M |
289M |
289M |
| Core Clock (Including DIspatch, texture units, and ROP units) |
675MHz |
730MHz |
540MHz |
| Shader Clock (Stream Processors) |
1.45GHz |
1.566GHz |
1.19GHz |
| Memory Clock |
1000MHz (2GHz DDR) |
1130MHz (2.26GHz DDR) |
700MHz (1.4GHz DDR) |
| Memory Interface |
128Bits |
128Bits |
128Bits |
| Memory Bandwidth |
32GB/s |
|
22.4GB/s |
| Frame Buffer Size |
256MB |
256MB |
256MB |
| HDCP Support |
Yes |
Yes |
Optional |
The physical design of the 8600 GTS is very similar to the former
7900 GS. Pictured below for a side by side comparison of the
XFX GeFORCE 7900 GS. One obvious change XFX made from its previous design was to expand the heatsink to cover all the RAM chips. Other than that, both cards are identical in layout and form factor. Dual DVI ports, PCIe power connector and single SLi adapter still remain the same.
PureVideo HD: Offloading 100% of HD Video!
One of the most exciting feature of the new 8600 and 8500 is a completely new video processing engine (VP2 + BSP + AES128 Engine) which offloads 100% of Blu-Ray and HD-DVD processing from the CPU. While the previous G80 core did come equipped with PureVideo HD functionality, the new core architecture has changed the way it works. Before the GeForce 8800 cards would off-load some of the cycles from CPU to GPU when decoding HD-DVD or BLU-RAY movies. Now with the 8600 and 8500 cards, the video processing load will be completely handled by the GPU, allowing the CPU to handle other computations and avoid framerate drops during video playback. This feature is especially appealing to users who are pairing these cards with midrange CPUs that would be stressed when decoding HD video, and NVIDIA's press package depicts their lower end cards as perfect companions with the 650i SLI or deluxe for multimedia systems. As you can see in the below illustrations the 8600 and 8500 are accelerating 2 additional steps in the decode procedure compared to the GeForce 7 series.
It is also worth noting that the 79xx and 88xx series both handle PureVideo HD processing in the same fashion. The 8600 is different, processing 4 of 4 steps instead of 2 of 4 which the previous PureVideo handled. Most likely in the case of the G80, the NVIDIA engineers didn't like the idea of spending anymore time reconstructing the silicon design to incorporate the new BSP engine that the 8600 GTS has. With that said, the 8600 or 8500 with the new PureVideo HD processing both look like nice accompaniments with a cheap CPU and NVIDIA 650i chipset based motherboard to make for an affordable HD decoding rig. Initially PureVideo HD support will be availble on Windows Vista, with Windows XP support appearing in June of this year.
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