Bad Athlon 64 design choice?

[Slaimus]

Can someone offer a counterpoint on why AMD chose to make the A64 single channel, but with the full opteron core?
I would think that a dual channel but 512k cache A64 would perform just as well, but cost AMD far less to produce the chip. It does not cost AMD much to put more pins on its chips, and since Operton/FX boards are 4 layer as well, I dont see it being too expensive to produce for MB makers.

 

[rgreen83]

Actually, IIRC, Opteron and FX boards(which are opteron boards) are 6 layers due to the high number/density of signal lines of 128bit memory and added HT links. Of course they were gonna reuse the opteron core for the athlon so they can better control die-to-package ratios. They only currently have one fab (fab 30) producing 64bit chips and it is easier to produce one line of wafers instead of two in the same fab. I dont know it they have a seperate line they could possibly do this on but switching back and forth would be a no-no in the ledger books.

So then most of that die goes to the 1024k cache, so it is the most expensive part of the die. They didnt want to cut off the most expensive part of the die because it would be too much waste. Less HT links and 64bit memory controller doesnt waste as much of the die and it hampers the performance enough to be a seperate line of processors.