pa1743@sdcc13.ucsd.edu (Jethro Bodean) (03/27/90)
If I have a Mac II plain w/o a PMMU chip would I be better off spending the ~$150 for the PMMU chip or the ~$230 for MacSprint II? From what I understand MacSp is basically a 32k cache for the 68020 alone and helps screen redraws and some math stuff. This computer has a 19" Color monitor and works A LOT in pagemaker and freehand etc so screen redraws take a while. But I hear that even with the 5meg I have I may need PMMU to use sys7.0 if it ever shows up as promised.... Any thoughts or experience with either product singly or comparatively? (or even other hardware in the price range..) = Mac II, 5 meg, 19" Radius 8 bit, 100meg, 1 800K = I'm not against doing the hardware stuff my self I'm an old pop it open Apple II hack... Any word would be appreciatted... Thanks! -Tod Kuykendall pa1743%sdcc13@ucsd.edu
lander@bulean.enet.dec.com (Vadim Lander) (03/27/90)
In article <9325@sdcc6.ucsd.edu>, pa1743@sdcc13.ucsd.edu (Jethro Bodean) writes... > >If I have a Mac II plain w/o a PMMU chip would I be better off >spending the ~$150 for the PMMU chip or the ~$230 for MacSprint II? You are talking about two different functionalities here. The answer is you want both. You want the MacSprint II board now to improve the speed and you'll want the PMMU chip later to take advantage of the virtual memory offered by system 7. - Vadim Lander
gillies@m.cs.uiuc.edu (03/30/90)
> If I have a Mac II plain w/o a PMMU chip would I be better off > spending the ~$150 for the PMMU chip or the ~$230 for MacSprint II? (1) The PMMU will actually *slow down* your computer. I believe the motorola chip has 1 more wait state than the apple chip. (2) Your computer, as it is, runs all the latest vaporware today! Therefore, no PMMU upgrade is necessary in order to run vaporware (system 7.0). Don Gillies, Dept. of Computer Science, University of Illinois 1304 W. Springfield, Urbana, Ill 61801 ARPA: gillies@cs.uiuc.edu UUCP: {uunet,harvard}!uiucdcs!gillies
daveh@cbmvax.commodore.com (Dave Haynie) (04/11/90)
In article <1460@bridge2.ESD.3Com.COM> ngg@bridge2.ESD.3Com.COM (Norman Goodger) writes: >In article <77800010@m.cs.uiuc.edu> gillies@m.cs.uiuc.edu writes: >>(1) The PMMU will actually *slow down* your computer. I believe the >> motorola chip has 1 more wait state than the apple chip. > As far as I know, this is incorrect. Installing the PMMU > removes the wait state, and does "not" slow down your Mac II. I don't know what the Apple MMU-replacement chip actually does. But the 68851 PMMU *ALWAYS* adds at least one wait state to a normal 68020 cycle. Nothing you can do about it. The worst part of it is that the MMU's bus timing is sloppy as compared with the 68020 timing, even though they use the same bus interface. So you can actually add two wait states with the PMMU, though not necessarily -- that's very dependent on the design of the system. The Mac II's memory system isn't fast enough for a 3 clock 68020 cycle anyway. The question is whether 4 or 5 clock memory cycles are actually used. If it's running 5 clocks, there's a real good chance Apple could have done 4 with a 68020 or 68030 instead of the 68020+68851, if they had been clever. They had the chance in the Mac IIx, but I don't think they started getting clever until the Mac IIci. >Norm Goodger SysOp - MacInfo BBS @415-795-8862 -- Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Too much of everything is just enough