Assuming words are spread uniformly throughout the

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Unformatted text preview: es a CPE of 2.00. In example B of Figure 5.33(a), both arguments src and dest are pointers to array element a[0]. In this case, each load by the pointer reference *src will yield the value stored by the previous execution of the pointer reference *dest. As a consequence, a series of ascending values will be stored in this location. In general, if function write_read is called with arguments src and dest pointing to the same memory location, and with argument cnt having some value Ò ¼, the net effect is to set the location to Ò ½. This example illustrates a phenomenon we will call write/read dependency—the outcome of a memory read depends on a very recent memory write. Our performance measurements show that example B has a CPE of 6.00. The write/read dependency causes a slowdown in the processing. To see how the processor can distinguish between these two cases and why one runs slower than another, we must take a more detailed look at the load and store execution units, as shown in Figure 5.34. The store unit conta...
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.

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