Path: utzoo!news-server.csri.toronto.edu!rutgers!psuvax1!wuarchive!uwm.edu!linac!mp.cs.niu.edu!bennett From: bennett@mp.cs.niu.edu (Scott Bennett) Newsgroups: comp.sys.next Subject: Re: Non-parity SIMS Message-ID: <1991Mar11.225744.2071@mp.cs.niu.edu> Date: 11 Mar 91 22:57:44 GMT References: <23938@hydra.gatech.EDU> <1991Mar11.045612.1764@mp.cs.niu.edu> <1991Mar11.101750.1@capd.jhuapl.edu> Organization: Northern Illinois University Lines: 51 In article <1991Mar11.101750.1@capd.jhuapl.edu> waltrip@capd.jhuapl.edu writes: >In article <1991Mar11.045612.1764@mp.cs.niu.edu>, bennett@mp.cs.niu.edu (Scott > Bennett) writes: >> In article <23938@hydra.gatech.EDU> gt5223b@prism.gatech.EDU (Doug Berkland) > writes: >>>What are non-parity SIMS? > [...] >> The new, 68040-based NeXTs can be configured either w/parity or >> w/o parity, as you prefer. I am told, however, that NeXT has screwed >> up the hardware design in those machines in a way that causes the use >> of parity memory to introduce wait states. > Hmmm. I'm not sure this is a screw-up. I believe the wait states are > only introduced when accessing memory--but most of the time (if all If it introduces wait states, then it is indeed a design flaw. Even IBM pee cees and clones thereof have parity memory that does not introduce wait states by virtue of being parity memory. If junky hardware like those machines can do it, any manufacturer's (yes, even NeXT's) ought to do it. > goes according to plan :^) you'll be running out of cache. In > practice, I doubt that the introduction of wait states will have much > impact. If the data cache is write-through, not write back, it could well make quite a difference. Does anyone have a 68040 manual yet? > [...] > On another note, the memory used in both the 68030 NeXTs and the 68040 NeXTs is too slow to avoid wait states on a 25-MHz bus. Does interleaving manage to reduce the wait states actually induced to a near-zero level in the NeXTs? > >c.f.waltrip > >Internet: > >Opinions expressed are my own. Scott Bennett, Comm. ASMELG, CFIAG Systems Programming Northern Illinois University DeKalb, Illinois 60115 ********************************************************************** * Internet: bennett@cs.niu.edu * * BITNET: A01SJB1@NIU * *--------------------------------------------------------------------* * "The good news is that Saddam Hussein will be tried for war * * crimes. The bad news is that the case will be heard by the * * Senate Ethics Committee."--quoted in _The_Wall_Street_Journal_ * **********************************************************************