Path: utzoo!attcan!uunet!samsung!brutus.cs.uiuc.edu!apple!mattd
From: mattd@Apple.COM (Matt Deatherage)
Newsgroups: comp.sys.apple
Subject: Re: II gs Caracteristics
Message-ID: <36001@apple.Apple.COM>
Date: 28 Oct 89 17:32:22 GMT
References: <8910161202.aa01399@SMOKE.BRL.MIL> <8193@microsoft.UUCP>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 38

brianw@microsoft.UUCP (Brian Willoughby) writes:
>>> I like to know some information about the II gs.
>>
>>>- 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
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.

>Brian Willoughby
>UUCP:           ...!{tikal, sun, uunet, elwood}!microsoft!brianw
>InterNet:       microsoft!brianw@uunet.UU.NET
>  or:           microsoft!brianw@Sun.COM
>Bitnet          brianw@microsoft.UUCP

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