Advanced Micro Devices Inc (AMD)

[yourbankruptcy]

wbmw, lets compare memory access of Opteron and P4. First see the memory latency for single P4 2.8 Ghz :

http://aceshardware.com/read.jsp?id=50000304

The latency is 28 ns for 64 byte strides, 90 ns for DDR 128 bytes and finally 113 ns for Rambus.

The see Opteron latency:

http://aceshardware.com/read_news.jsp?id=60000410

80 ns for 1P system,
115 ns for 1 hop
150 ns 2 hops
190 ns 3 hops

Now go here:
http://www.hotchips.org/archive/hc14/hc14pres_pdf/28_AMD_Hammer_MP_HC_v8.pdf

4P Opteron has the average diameter 1.17 hops
8P Opteron has the average diameter 1.64 hops

So the memory access latency is 121 ns for 4P system and 137 ns for 8P Opteron system. Its unclear how many bytes in stride it can transfer with this latency.

As you see memory latency of 4P Opteron is comparable with 1P P4 w. 533 Mhz bus.