Intel 925X and Socket 775 Platform: PCIe and DDR2

DDR2 – Intel Goes the Lonely Route Again

Just as with PCI Express technology, there has been much debate surrounding the DDR2 memory technology.  Everyone from AMD, to the various memory manufacturers, to the analysts that cover the market, have tipped their hat in with an opinion on Intel’s push of DDR2 memory technology.

DDR2 memory brings two big changes to the memory world, at least for now: first, there is an increase in the available bandwidth in DDR2 memory; and second, there is an increase in the latency in DDR2 memory. 

The former, increased bandwidth, is of course a positive for the PC industry.  DDR2, running at 533 MHz speeds (266 MHz x 2) can deliver 4.3 GB/s bandwidth on a 64-bit (single channel) memory controller or 8.6 GB/s on a 128-bit (dual channel) memory controller at its theoretical peak.  However, that additional speed comes at the cost of latency.  Our memory that we used during our testing had a CAS latency of 4 clock cycles.  That is twice as high as we are used to seeing in our DDR400 configurations running at CAS 2.  The other memory latencies follow suit, and our memory is speced out at 4-4-4 CAS 4 — just not impressive after living in the world of super-fast DDR400, and beyond, memory for so long. 

Here is a look at the three brands of DDR2 memory that I have had the chance to play with thus far.  Kingston, Micron and Crucial-branded Micron modules. 

You can see from the above image that these are all DDR2-533 modules rated at Cas Latency 4.

Here we see a DDR2 DIMM placed on top of a DDR DIMM to show you the physical changes that have taken place on the memory; it’s not much.  The pin has been moved to the left (from this view) to avoid having people install the wrong kind of memory in their motherboard.  The pin count on the DDR2 modules has moved up to 240-pin, up from 184-pin, on the original DDR modules.  Also, DDR2 is using lead-free micro BGA packaging for the actual chips.