Polesia wrote:

I noticed that a lot of the GPUs from the AMD HD 2000 to HD 4000 series feature both GDDR4 and GDDR3 variants. I've heard multiple times that performance is pretty much the same (though have never seen a benchmark). That being said, what was the point of having a GDDR4 variant? Was it just for marketing or was there a tangible benefit?

I only remember 2600xt, 2900xt, 3870 and 4670 having GDDR4 versions, maybe there were more...
it could clock higher than GDDR3 at the time, so there was an advantage, but I don't think it helped performance much.

GDDR4 is just slightly modified GDDR3, which failed expectations. Very similar to early GDDR2 on GeForce FX 5800. Quickly died after GDDR3 achieved clocks beyond 2000mhz.

I have the X1950 XTX with GDDR4 too.

GDDR4 is barely faster because the latency gets cranked up to hit only somewhat higher clock speeds.

It should be said, that another problem of GDDR4 besides latencies was excess heat produced by memory chips.

After much digging I found a review comparing the GDDR4 and GDDR3 versions of the Radeon HD 3870: https://techreport.com/review/14654/diamond-r … -1gb-video-card

Unfortunately the VRAM size between both cards are not the same (1GB GDDR3 vs 512 MB GDDR4), so it's not perfect. It seems that the GDDR4 version does noticeably better in the single texture fillrate test from 3DMark06. It also idles 5 watts lower. Real game performance favors the GDDR3 version, but the core is factory overclocked and they are cranking resolution and AA quite high to test the large VRAM size.

There's also some Radeon 2900XT versions with whopping 1gb of GDDR4 memory.

And 2GB GDDR4 FireGL V8650. 😈