lengge@ethz.UUCP (Thomas Lenggenhager) (07/27/88)
Hi all,
I have an important matter to discuss (important for me, interesting for you?).
Next month, I hope, I will get some of the very first ** 4 Meg-SIMMs **, but a
friend of mine told me the other night that there are problems with some piece
of system software that the new chips won't be recognized.
This is what I know and here are my questions. Can anyone out there help?
1) 4 MB SIMMs won't be recognized at all in Plusses and SEs, right? Why not,
it's really a pitty :-(
2) In the Mac II, the following things happen:
- The motherboard looks at the first 4 SIMMs and checks if these are 16 MB
parts. If it doesn't find them, the next lower MB (KB) SIMMs are searched
for (16MB -> 4MB -> 1MB -> 256KB).
- Then, the second 4 SIMMs are checked if there are the same SIMMs as in the
first four rows or if there are lower parts installed.
3) Is there somewhere a problem for me that makes it difficult or impossible to
access this memory with the Mac OS? (I think, with Unix that should be no
problem).
Thank you very much for your help. As soon as I'll get them I will send a short
report on these SIMMs.
Gary T. Czychi University of St.Gallen, Switzerland
====
CZYCHI@CSGHSG52.BITNET (also: CSGHSG53,CSGHSG5A)
A-friends-account.UUCP :-)
Tel.: --41 / 71 / 27 52 68
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Schorenstr. 11a Hochschule St.Gallen
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Z.Hd. Herrn Gary Czychi
CH - 9000 St.Gallenkorn@eris.berkeley.edu (Peter "Arrgh" Korn) (07/29/88)
In <563@ethz.UUCP>, lengge@bernina.UUCP (Thomas Lenggenhager) said: >Next month, I hope, I will get some of the very first ** 4 Meg-SIMMs **, but a >friend of mine told me the other night that there are problems with some piece >of system software that the new chips won't be recognized. >... >1) 4 MB SIMMs won't be recognized at all in Plusses and SEs, right? Why not, > it's really a pitty :-( True. The Mac Plus & SE were simply "designed that way". Perhaps someone at Apple could spell out the engineering reasons; my personal guess was that it turned out (probably) to be a fair amount cheaper to do it that way. In any case, while there is address space on the 68000 to have two of those SIMMs filled with 4MB parts, there isn't space for all four to be filled and still have anything left over for memory-mapped i/o (see my response to #3 below...). >2) In the Mac II, the following things happen: >- The motherboard looks at the first 4 SIMMs and checks if these are 16 MB > parts. If it doesn't find them, the next lower MB (KB) SIMMs are searched > for (16MB -> 4MB -> 1MB -> 256KB). >- Then, the second 4 SIMMs are checked if there are the same SIMMs as in the > first four rows or if there are lower parts installed. It's my understanding that 4MB parts are at the top of that loop, and not 16MB; making the max you could go directly on the motherboard 32Meg. But I haven't poked around the Mac Family Hardware Ref. manual in a few months and might well be wrong on this one. >3) Is there somewhere a problem for me that makes it difficult or impossible to > access this memory with the Mac OS? (I think, with Unix that should be no > problem). The MacOS in versions 6.0 and below runs in 24-bit addressing mode, making the maximum amount of RAM addressable 16MB. Of that 16, 1 goes to each of the six card slots, and much of another Meg is used for memory-mapped I/O, leaving something not much over 8 Meg left (again, I haven't been sniffing around the Hardware Ref. for a while & my numbers may be a tad off...). With 6.01 coming so quickly on the heels of 6.0 I would doubt that we're out of 24-bit addressing and into 32-bit. What this all means is that we can't talk to more than 8MB of SIMMs on the motherboard currently in the Mac OS. Running A/UX this shouldn't be a problem. I don't have any direct knowledge of anyone testing SIMMs bigger than 1 Meg in a MacII under A/UX, though Apple says that it should work (again in that wonderous Mac Family Hardware Ref. manual). >Thank you very much for your help. As soon as I'll get them I will send a short >report on these SIMMs. I would be very interested in that report... Peter -- Peter "Arrgh" Korn korn@ucbvax.Berkeley.EDU {decvax,hplabs,sdcsvax,ulysses,usenix}!ucbvax!korn
mto@homxb.UUCP (M.ODONNELL) (07/29/88)
> > parts. If it doesn't find them, the next lower MB (KB) SIMMs are searched > > for (16MB -> 4MB -> 1MB -> 256KB). > >- Then, the second 4 SIMMs are checked if there are the same SIMMs as in the > > first four rows or if there are lower parts installed. > It's my understanding that 4MB parts are at the top of that loop, and not > 16MB; making the max you could go directly on the motherboard 32Meg. But > I haven't poked around the Mac Family Hardware Ref. manual in a few months > and might well be wrong on this one. > leaving something not much over 8 Meg left (again, I haven't been sniffing Does this mean that when (hopefully relatively cheap) 2M X 1 bit chips are available (really 4M X 1s that are "half bad") that they can't be recognized? This may sound picky, but I understand that there have been serious yield problems with 4M chips. If that continues into production, there may be alot of 2Ms around until the problems are straightened out. With the way the "RAM cycle" is slowing down, that period may last a while. Marty O'Donnell ihnp4!homxb!mto