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Page 441
0441-01.gif
Figure 7.15
Address distribution.
EXAMPLE 7.3
Consider a memory consisting of 5 modules of 4 words each (representing 20 words, 0 through 19).
A mod 4
A mod 5 module address
word address
0
1
2
3
4
0
0
16
12
8
4
1
5
1
17
13
9
2
10
6
2
18
14
3
15
11
7
3
19

That is, address 11 will be contained in word 3 (11 mod 4) and module 1 (11 mod 5). Of course, the above pairing works equally well for pairs of the form (a1, a2):
a1
=
A mod 2k - 1,
a2
=
A mod 2m.

For the problem at handmanaging strideclearly some mods of the form 2k ± 1 are better than others, as they are prime. Thus, if about 4 memory modules were required, we would choose 5 as the prime number of modules.
Similarly, we have:
Approximate number of modules required (determined by Bw requirements)Choose prime of form 2k ± 1
4
5
8
7
16
17
32
31
64

 
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