AMD 64 manual Next, we increase the number of background threads to six, running on

Performance Guidelines for AMD Athlon™ 64 and AMD Opteron™	40555 Rev. 3.00 June 2006
ccNUMA Multiprocessor Systems

VERY HIGH: Total Time for both threads (write-write)

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		186%	195%
158%
		1 Hop	1 Hop
	0 Hop	1 Hop
		NO	1 Hop
	0 Hop	Xfire	Xfire

0.0.w.0 1.0.w.1 (0 Hops) (0 Hops)

0.0.w.1 1.0.w.3 (1 Hops) (1 Hops)

0.0.w.1 1.0.w.0 (1 Hops) (1 Hops)

Figure 8. Crossfire 1 Hop-1 Hop Case vs No Crossfire 1 Hop-1 Hop Case under a Very High Background Load (High Subscription)

Next, we increase the number of background threads to six, running on:

•Node 0 (Core 1)

•Node 1 (Core 1)

•Node 2 (Cores 0 and 1)

•Node 3 (Cores 0 and 1)

Each of these background threads reads a local 64 MB array and the rate of memory demand of each thread is very high. A very high rate of memory demand implies that each of the background threads is demanding a memory bandwidth of 4GB/s, as shown in Table 1 on page 16.

No free cores are left in the system. This the fully subscribed condition.

As shown in Figure 9 on page 29, when the background load and level subscription are increased to the maximum possible, the no crossfire case becomes slower than the crossfire case.

28 Analysis and Recommendations Chapter 3