Rambus DRAM Part 2: Performance

As we've known since last November, there are three flavors of RDRAM: PC800, PC700 and PC600, all running at different clock speeds – 400MHz for PC800, 356MHz for PC700, and 266MHz for PC600.  As you can probably guess, the performance for the latter two types of RDRAM would be lower than that of PC800, but by how much is the question? 

In order to find out, we used the ASUS P3C-E, which is one of the three motherboards we've seen that allows for the manual adjustment of the RDRAM clock frequency (the other two being the Intel OR840 and the AOpen AX6C/L) and ran a few benchmarks.

The difference between PC800 and PC700 RDRAM doesn't seem to be too great, but once you hit PC600 RDRAM the performance drop is definitely noticeable and unacceptable.

In this case, PC800 offers a 5% performance improvement over PC600. While that may not seem like a lot, for the price you're paying, PC600 isn't exactly close enough.

Under Quake III Arena we notice a huge performance difference between the slowest PC600 RDRAM and the fastest PC800, 15.8 fps is quite a bit even if it's only at 640 x 480.

At 1024 x 768 x 32, other limitations kick in before the difference between PC600 and PC800 RDRAM in terms of latency and bandwidth can take their toll. This explains the relatively small difference between the three memory speeds.