Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!cs.uoregon.edu!geriatrix.cs.uoregon.edu!mkelly
From: mkelly@geriatrix.cs.uoregon.edu (Michael A. Kelly)
Newsgroups: comp.sys.mac.hardware
Subject: Re: How much RAM can the IIcx handle?   SUMMARY and new ?
Message-ID: <1991Apr12.211736.4240@cs.uoregon.edu>
Date: 12 Apr 91 21:17:36 GMT
References: <1991Apr11.165406.6175@cs.uoregon.edu>
Sender: usenet@cs.uoregon.edu (Netnews Owner)
Organization: Department of Computer Science, University of Oregon
Lines: 51

In article <1991Apr11.165406.6175@cs.uoregon.edu> mkelly@obelix.cs.uoregon.edu (Michael A. Kelly) writes:
>
>I've heard that the IIcx can only access about 13-14 Meg of RAM with the
>virtual memory feature of System 7.  Is this true for RAM in general?
>E.g., if I go out and buy four 4-meg simms and plug them into my IIcx, and
>leave four 1-meg simms in the other bank, will I have 20 meg of RAM at my
>disposal?
>

Thanks to all who replied to my question.  This reply (from Dave Platt)
sums them all up:


That's correct;  yes;  and no... in that order.

The IIcx ROMs are not "32-bit clean."  This means that the machine can
run only in 24-bit mode... 24 bits of address space give you a
16-megabyte address range.  One meg is consumed by the ROM, and one meg
is consumed by each NuBus card... typically leaving you 14 megs of
address space that can be mapped into RAM.

If you install 4 4-meg SIMMs, you might as well pull the old 1-meg SIMMs
out and use them in another machine.  Until Apple decides to upgrade the
IIcx ROMs (if they ever do), you won't be able to use more than 16 megs
of address space, either direct or VM-paged, regardless of the amount of
RAM you have installed.

It's possible that you might be able to use a third-party utility to
access the above-the-waterline memory as a RAMdisk... Connectix in Menlo
Park, CA may have something along this line.

-- 
Dave Platt                                                VOICE: (415) 813-8917
                    UUCP: ...apple!ntg!dplatt
 USNAIL: New Technologies Group Inc. 2468 Embarcardero Way, Palo Alto CA 94303



So, if I buy four 4-meg simms and put them in my IIcx, and then later upgrade
to a IIfx (or later), could I use those 4-meg simms in the new machine?  I
hear the IIfx requires special memory chips - do they work in other machines?


Thanks,

Mike.
-- 
_____________________________________________________________________________
Michael A. Kelly                                   America Online: Michael792
mkelly@cs.uoregon.edu                                  Compu$erve: 73567,1651
_____________________________________________________________________________