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From: toddpw@tybalt.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple
Subject: Re: The Apple IIf
Message-ID: <1990Feb24.065706.4534@spectre.ccsf.caltech.edu>
Date: 24 Feb 90 06:57:06 GMT
References: <900222.14492460.054933@UWEC.CP6> <NAGENDRA.90Feb23124032@bucsf.bu.edu> <1990Feb23.190539.18534@ux1.cso.uiuc.edu>
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Organization: California Institute of Technology
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cs122aw@ux1.cso.uiuc.edu (Scott Alfter) writes:

>imagine that the increased circuit complexity of a "IIf" would generate enough
>heat without any cards installed that a fan would become a "must."

Well, most of the complexity would be in the chip set, and those run pretty
cool from what I hear, except at high frequencies, which we will have to deal
with. A built in fan is a simple must these days, period.

I figure that a fan sucking in the front, over the motherboard and between the
slots, and out the back would do just fine. That's almost a direct quote from
the //f paper; did you read it real late or just skim it or something? Or my
prose just sucks for clarity. (I can believe that.)

>Here's an idea for getting the system disk into memory:  make an EEPROMdisk.

I said almost that. EEPROMS are nice, but they are too darned expensive to make
a system disk out of. You can buy 128K EPROMs for $20 apiece from JameCo, so
a 1 meg boot disk would take eight chips or ~$160.

Use one 2864 EEPROM as your directory blocks and pointers to overwritten stuff,
and treat the thing like a WORM disk. Writing files should be done by a special
installer that takes care of figuring out which blocks have been overwritten
and alerting the ROM disk driver to it. 12V EPROMs are much more common and
can be programmed by using a simple transistor switch to the +12V supply.
When you have exhausted your free space, you will probably just back up to
floppy and then erase them all. More sophisiticated things could be done but
that's for third parties.

There should be two ROM slots, one for Bank $Fx ROM, maybe an official ROM SIMM
from Apple, and another for the EPROM disk. All the address/data latches and
counters (this is a slinky type remember) could go on card, they are just PALs
anyway. This way the card is a cheap as it can be, and the motherboard is still
pretty cheap with the extra cost kept to the slot and all its wires plus a few
chip selects.

Todd Whitesel
toddpw @ tybalt.caltech.edu