Blameless

During my time researching and playing with P45 boards, I (and many others) have noticed a few things:

1. The die of the chipset itself is almost the same size as the P35, even though the P35 is a 90nm part while the P45 is built on a 65nm process.

2. The P45 requires much looser tRD (aka performance level, aka static read control) values than the P35 or X38/X48.

3. The memory performance of the P45, even with the looser tRD is, overall, no worse than, and often superior to the P35 and X38/X48. This is especially true when it comes to write and copy performance, and most real world tests.


Some have suggested the extra die size is due to the area designated for Intel's GMA X4500HD graphics (so they can use the same dies for the P45 and G45, and simply disable the graphics on the P45). This may have some truth to it, but since the P35 is also likely to have had room for the previous GMA I do not think this tells the whole story. Certainly the 4500 is going to need more transistors than the former GMA, but that many more?

The changes in memory performance (somewhat worse internal latencies, but improved copy and write speeds) follow the exact same pattern as what happens to a CPU or harddrive when you significantly increase it's cache size. Anytime intel has enlarged the L2 cache of it's chips, the latency of that cache get slightly worse, but system memory write speeds improve. This is exactly what I have seen moving from the P35 and X48 chipsets I have tried to the P45.

I think one of the major changes to the P45, that explains some of the extra transistor count, the requirement for a looser tRD, and it's increased performance is a larger on-chip buffer/cache than what was on previous chipsets.

I could be wrong, but that's my theory.

Thoughts? Anything I missed?