Path: utzoo!attcan!uunet!samsung!shadooby!mailrus!purdue!mentor.cc.purdue.edu!mace.cc.purdue.edu!asd
From: asd@mace.cc.purdue.edu (Kareth)
Newsgroups: comp.sys.apple
Subject: Re: II gs Caracteristics
Message-ID: <3442@mace.cc.purdue.edu>
Date: 29 Oct 89 05:43:17 GMT
References: <8910161202.aa01399@SMOKE.BRL.MIL> <8193@microsoft.UUCP> <36001@apple.Apple.COM>
Organization: Purdue University Computing Center
Lines: 39

In article <36001@apple.Apple.COM> mattd@Apple.COM (Matt Deatherage) writes:

>brianw@microsoft.UUCP (Brian Willoughby) writes:
>>>>- How many memory it can adress ?
>>>   Up to 8 Mbytes
>>
>>Make that 16 Mbytes.  Both video RAM and ROM memory are above the 8 Meg
>>boundary (I don't know where the sound memory is).  Generally, RAM might
>>be limited to 8 Meg on cards from Apple computer, but it is possible to
>>add RAM above the 8 Meg boundary, so the total linearly addressed RAM can
>>be much more than 8 Meg.

>That's a little misleading.  The processor can address 16 MB, and the ROM and
Very.

>slow RAM in the system are both in the high part of that address space.
>However, the hardware can't address fast RAM above the 8 MB mark, and the
>Memory Manager doesn't look for it.  This has an effect such that if you put
>more than a total of 8 MB of RAM in the system through an expansion card, the
>first 8 MB are all you'll get to use.

>Brian's right; it *can* go higher, but it's misleading to think you can buy
>a 16 MB RAM card and get to use all of it.  You can't.  Even with special
>slot-ROM tricks to get to the memory, it's not accessible to DMA peripherals.

I'd heard (way back in the beginning of the dawn of the IIgs) that Apple
had specifically put aside 8 meg of ROM space for their personal use in
the future.  Actually, shouldn't that be about 7.5 or so?  They did
allot 512K for a ROMdisk, but what can you do with 512K?  Sure, you can
put ProDOS 8 on there and maybe a few other things, but you can't really
get something like GS/OS on there.  Seems kinda odd that Apple would set
aside 8 meg of space for future ROM upgrades.  I mean, shit, what are
you gonna put there?  UNIX????  OH!  You ARE?????  Well, now maybe I
underestimated you guys.  Then again, it looks like I'm dreaming again
while I'm posting.  Matt's explanation seems to make more sense than the
one I heard.  Of course, then the question is, why did Apple choose to
limit the memory space by over half?  Owell, the world may never know.

-kareth.