david@star2.cm.utexas.edu (David Sigeti) (12/12/90)
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). -- David Sigeti david@star2.cm.utexas.edu cmhl265@hermes.chpc.utexas.edu
davidsen@sixhub.UUCP (Wm E. Davidsen Jr) (12/14/90)
In article <DAVID.90Dec11164329@star2.cm.utexas.edu> david@star2.cm.utexas.edu (David Sigeti) writes: | Does anyone out there know which manufacturers (if any) of 486 systems | or motherboards actually use the 486 burst mode? AIR (sorry I don't remember the acronym) does. They sent me some support info, showing that with burst mode you get very little from external cache. They sell boards with and without, so I can't say they're trying to convince you to buy what they sell. They advertise in the back if _Info World_ and sell very sharp on the phone. -- bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen) sysop *IX BBS and Public Access UNIX moderator of comp.binaries.ibm.pc and 80386 mailing list "Stupidity, like virtue, is its own reward" -me