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GeForce 6600GT AGP Preview

The AGP version of the GeForce 6600GT is announced today. We evaluate its performance in seven of the latest games to see the value it brings to your gaming experience.

Introduction:

What has become quite possibly the best mainstream video card is now catering to an even wider audience, and thank goodness for that. NVIDIA announced the new GeForce 6600 series of video cards back in mid August and we did a short technical preview here of this new series. To sum up the technical specifications, the 6600GT is an 8 pipeline / 3 vertex unit video card clocked at a very high 500MHz GPU frequency using GDDR3 memory on a 128-bit memory bus clocked at 500MHz (1GHz DDR). The vanilla 6600 also has 8 pixel pipelines and 3 vertex units, but it has a frequency reduced GPU core speed of 300MHz and uses DDR1 memory clocked at the manufacturer's discretion.

Both video cards are using the NV43 GPU, which is built on the 11nm manufacturing process and fully supports every single feature that the GeForce 6800 series (NV40) possesses. This means they support Shader Model 3.0, Floating Point 16 Frame Buffer with OpenEXR support, UltraShadow II, and the Video Processor.

Almost a month later NVIDIA revealed to the world just how powerful their GeForce 6600GT really was. We previewed the GeForce 6600GT PCI-Express. At the time all we had to compare it to was the ATI Radeon X600XT which was the direct competition for it when we did the preview. The GeForce 6600GT easily walked away the winner. It wasn’t until later that month when ATI launched their performance mainstream video card the Radeon X700XT that we could finally pit the GeForce 6600GT against its proper competitor. The results quite shocked us, with the GeForce 6600GT coming out on top in almost every single game tested. Clearly the PCI-Express GeForce 6600GT gave us a better gaming experience for the price of $199.

The only issue with the GeForce 6600GT at the time was that there was only the PCI-Express version with no solid timeframe on when we would see AGP parts. PCI-Express motherboards have not yet made it to retail for AMD systems, and try as they might, PCI-Express adoption isn’t moving as fast as some would like. AGP is here to stay for a while, and we don’t see it falling off any major roadmaps. Thankfully, NVIDIA realized this and has pushed out an AGP version of the GeForce 6600GT!

HSI Bridge Chip

The NV43 is a native PCI-Express GPU, therefore NVIDIA was able to use their High Speed Interconnect (HSI) bridging chip to bridge from a PCI-E interface to an AGP8X interface instead of having to fabricate a new GPU, saving time and money.

There has been a lot of controversy over bridge chips, but the controversy mainly stems from bridging a native AGP video card to the PCI-Express interface, with concerns of latency and overall bandwidth with this design. With the GeForce 6600GT, NVIDIA is bridging a native PCI-Express chip to the AGP8X interface, therefore any controversy over latencies and bandwidth is not applicable in this scenario since the chip itself is native PCI-E to begin with.

The High Speed Interconnect chip runs independent of the GPU and bridges PCI-E to AGP8X or AGP8X to PCI-E based on the 1.0a specification of PCI-Express. It is a bi-directional chip that supports internal speeds up to AGP16X, which is 4.2GB/sec of bandwidth upstream and downstream. This means the core logic circuitry inside the 6600GT can still run with the PCI-Express bandwidth of 8GB/sec theoretical maximum (4GB/sec up and down) which is the same bandwidth of AGP16X inside the HSI chip. It then gets translated down to AGP8X at 2.1GB/sec across the physical interface on the motherboard.

It is very clear that this HSI bridge chip gives NVIDIA a lot of options. They are able to produce native PCI-E video cards while making the same GPU work on the AGP platform very quickly. And while you have likely heard much FUD about “bridge chips” being the devil in terms of latency penalties, this just not seem to be the case with NVIDIA’s GeForce 6600GT AGP.

The GeForce 6600GT AGP

The NVIDIA power supply recommendation for the GeForce 6600GT AGP version is a minimum 300 watt power supply. As you can see, it does have an external Molex connector that is needed to supply enough power to this video card since the AGP bus cannot provide as much power as the PCI-Express bus slot can.

You can see how they have repositioned the heatsink fan unit to accommodate space for the HSI bridge chip which requires its own heatsink. Under full load the HSI heatsink became very hot to the touch.

In the comparison shot above you can see the PCI-Express 6600GT on top and the AGP 6600GT on the bottom. They are the same physical size, but they do have a different PCB layout.

Our sample came with dual DVI and TV-Out on board, so you may see such options in retail. The RAM being used is Samsung GDDR3 rated at 2ns for a maximum 500MHz operation. Our card's memory was clocked at 450MHz memory (900MHz DDR).