🚀 go-pugleaf

Does anyone out there know which manufacturers (if any) of 486 systems
or motherboards actually use the 486 burst mode?  In a recent review
of 33MHz 486 systems in PC Magazine there was a cryptic comment about
"lack of support for the burst mode of the 486" but there was no
elaboration and no discussion of the issue in the individual reviews.

For those who wonder what I am talking about, the burst mode is a fast
way of filling a (128-bit) line in the 486's internal cache.
Normally, a memory read requires two clock cycles.  When the 486 is
filling a cache line, however, it can accept successive (32-bit) reads
in a single clock cycle each, if the surrounding circuitry supports
it.  Thus, filling a cache line can be accomplished in five clock
cycles (one to assert the starting address plus one for each 32-bit
read) rather than eight clock cycles (two for each 32-bit read).

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David Sigeti    david@star2.cm.utexas.edu    cmhl265@hermes.chpc.utexas.edu