Memory Access Example

• Repeatedly accessing 1MB of REAL*8 on the SP2

1MB = 244 pages * 4096 bytes;

REAL*8 = 8 bytes

4096 / 128 bytes = 32 lines/pg

128 bytes / 8 bytes = miss every 16 elements

32 misses/pg * 8 cycles/miss = 256 cycles/pg

1MB = 256 pgs

36 cycle TLB miss per page

256 * (36 + 256) = 73728 cycles wasted per iteration

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