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Content
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MMIXware Version
mmix-20131017
Bug Reported
Initial: 17/11/2014
Author
Laurent Desnogues
Description
In mmix-config, section 36, ring_size is computed
to be greater than the maximum waiting time.
The time to read a cache line from memory is mem_addr_time+n*j
where j is the maximum of mem_read_time and mem_write_time;
and n is the number of bus_words per cache line.
The number of bytes of a cache line is in the bb field of the cache;
and this number is used to initialize n before dividing by bus_words.
This can result in a ring_size that is too large by a factor of 8.
It will not result in an incorrect execution of the simulator, but allocates more memory
than necessary.
Proposed Patch
Scale bus_words by 8 in the line that rounds n up and determines the maximum number of
bus_words per cache line.
@x
n=mem_addr_time+((int)(n+bus_words-1)/bus_words)*j;
@y
n=mem_addr_time+((int)(n+bus_words*8-1)/(bus_words*8))*j;
@z
Discussion
Laurent Desnogues: That looks OK, though you could have used mem_bus_bytes.
Martin Ruckert: That's right, I will use mem_bus_bytes instead.
instead of bus_words*8.
Status
Fixed in the repository, Rev. 84, on 2014-11-18.
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