Well, the very same PC-800 memory that debuted over two years ago with the i820 chipset is still widely in use today without any modifications other than a big reduction in cost. For those that predicted that RDRAM, and Rambus with it, would not be able to survive amongst the cheaper SDRAM and DDR SDRAM, we can only say that time has proven them wrong. RDRAM is still the memory of choice for the Pentium 4 platform, not bad for a product and a technology that debuted two years ago and is still able to compete.

However Rambus isn't waiting for things to happen and realizes that PC-800 is getting a bit dated. As with almost any product these days they took the obvious step of increasing the clockspeed of their modules. PC-1066 and PC-1200 is what we can expect to see within the next year, whereas they'll also be moving from a 16-bit module to a 32-bits module. Which means that in case of the i850 chipset you'll only have to stick in one module instead of two, if the motherboard supports it that is.



Fig 4. Rambus PC-1066 capable RDRAM, these are actually cherry-picked and verified PC-800 modules and were also able to reach PC-1200 speeds.

Naturally PC-1066 and PC-1200 do not offer anything substantial over PC-800 but the increase in clockspeed and with that larger memory bandwidth. PC-1066,which will be used by upcoming Pentium 4 chipsets, will run off of a 133MHz bus and will offer 2.1GB/s of bandwidth, that's a 33% increase over PC-800. Naturally it needs no further explanation that PC-1200 offers a 50% increase in bandwidth, 2.4Gb/s total, over PC-800. However no details are given as of yet as to what busspeed the PC-1200 will be running off of.

Rambus is also moving away from a six-layer requirement for motherboard PCBs using their modules and the actual modules themselves. The first four-layer motherboards are actually already shipping, with a cost reduction for Pentium 4 motherboards of up to $25. With their 4i architecture Rambus will also be moving towards a four-layer implementation of their modules. Actually all of the upcoming Rambus modules, and also their next generation parts will feature exclusively as a four-layer implementation on both the motherboard and the modules.

In the next few pages we'll be looking at PC-1066 and PC-1200 memory performance by using a 2GHz Engineering Sample Pentium 4, an Asus P4T-E motherboard and PC-1066 RDRAM Samsung RIMMs provided to us by Rambus. We'll keep a close eye on the performance delta offered by both PC-1066 and PC-1200 and especially whether the Pentium 4 benefits from the higher memory band and higher busspeeds.