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Re: KA48 System Board Specification (Re: KA48 / VAXstation VLC cache question)
Now interestingly the KA48 System Board Specification also sheds light
on the everlasting question how much cache a SOC really has (was also
discussed here), ranging from 5 KB to 8 KB. Even DEC documents had
If I understand section 2.1, sentence 4 correctly, 6 KB are
"guaranteed" as minimum at least. Sounds plausible. So our CPU ID
strings are virtually correct printing out "6KB L1 cache".
"the processor chip has 8 KBytes of on-chip cache to improve execution
times by minimizing the performance required of the memory subsystem.
The cache is an eight set direct mapped write-through cache. To
improve manufacturing yield, one or more of the eight sets may be
disabled during the chip test process, allowing for possible die
defects without causing the entire chip to be rendered unuseable. It
is likely that a minimum of six sets will be functional."
Nevertheless, can anyone think of a procedure to determine the real
cache size programmatically and reliably? Would be fun to compare
different machines, also VLC and KA660.
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