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From: lemke@radius.com (Steve Lemke)
Newsgroups: comp.sys.mac.hardware
Subject: Re: IIfx memory config. with and w/out 32-bit addressing
Message-ID: <1439@radius.com>
Date: 25 Apr 91 17:12:31 GMT
References: <5714@media-lab.media.mit.edu.MEDIA.MIT.EDU>
Lines: 33

mjkobb@media-lab.media.mit.edu.MEDIA.MIT.EDU (Michael J Kobb) writes:

>  Let's imagine that I suddenly have enough money to upgrade my IIx to a IIfx
>(ha!).  So now, I need to buy memory.  If I buy four 4-Meg SIMMS, and 4 1-meg
>SIMMS, I now have 20Mb of physical RAM.

Let's imagine that instead, you purchased a Radius Rocket 68040 accelerator
board to stick into one of your IIx NuBus slots (HA!).  Now, let's assume
that you _already_ have 8mb of memory on your IIx motherboard.  You simply
move that memory to the Rocket board, and find some old 256K simms (four, to
be exact) to stuff into your motherboard - enough for your Mac to start up
and switch over to the Rocket.  Well, you just start up your system and
presto, you're running faster than you would've been with the IIfx upgrade,
and you have money left over too!!

>  Okay, fine.  In order to address that much memory, I need 32-bit addressing
>turned on (in System 7).  My question is, how much memory will I see if I turn
>32-bit off?  (i.e. if I need to run some non-32-bit-happy software)

If you turn 32-bit off on a IIci, IIfx or IIsi, the most you'll see is 8mb of
real (physical) RAM.  You can go up to 13mb, however, if you enable virtual
memory.  Of course, if you want to use big simms, you can go all the way to
128mb of RAM on the Rocket board (using 16mb simms)...

This imaginary scenario provided as a courtesy to those who might be
considering IIfx upgrades but are afraid that the IIfx might be too slow.  :-)

--Steve

-- 
----- Steve Lemke, KC6QDT - Software Engineering, Radius Inc., San Jose -----
----- Reply to: lemke@radius.com -- U.C. Santa Barbara ECE Class of '89 -----
----- "I'm not a UNIX wizard, but I play the Postmaster at radius.com." -----