AMD ATHLON 64 - Manual (Page 28)

28 Analysis and Recommendations Chapter 3
40555 Rev. 3.00 June 2006
Performance Guidelines for AMD Athlon™ 64 and AMD Opteron™
ccNUMA Multiprocessor Systems
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.
VERY HIGH: Total Time for both threads (write-write)
158%
186%
195%
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
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)
0 Hop
0 Hop
1 Hop
1 Hop
NO
Xfire
1 Hop
1 Hop
Xfire