Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!mintaka!daemon From: jtw@lcs.mit.edu (John Wroclawski) Newsgroups: comp.sys.mac Subject: Re: Nix on mixing memory speeds? Message-ID:Date: 23 Sep 89 17:54:00 GMT References: <11979@cit-vax.Caltech.Edu> <4002@phri.UUCP> <2040@leah.Albany.Edu> <1989Sep23.010904.7650@NCoast.ORG> Sender: daemon@mintaka.lcs.mit.edu (Lucifer Maleficius) Followup-To: comp.sys.mac Distribution: usa Organization: MIT Home for Wayward Triumphs Lines: 21 In-reply-to: allbery@NCoast.ORG's message of 23 Sep 89 01:09:04 GMT In article <1989Sep23.010904.7650@NCoast.ORG> allbery@NCoast.ORG (Brandon S. Allbery) writes: There is, by and large, only *one* case where the memory speeds would have to match: if the memory storage system accesses more than one memory chip at the same time, all of those chips must be the same speed or the memory access hardware will get a severe case of heartburn.... Jees, everybody's -so- confused. The main memory system of the Mac is a simple clocked design with completely fixed timing. What this means is that the SIMMs must produce data X time after they are asked. Period. It doesn't matter if they do it faster than that, and it doesn't matter if they do it at different speeds, as long as the data is ready when the CPU needs it. Perhaps this nonsense about needing the same speed for all the SIMMs in a bank got started because the -size- of all the SIMMs in a bank must be the same. Who knows. John T. Wroclawski - MIT Lab for Computer Science - jtw@lcs.mit.edu