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From: tribby@hpindwa.cup.hp.com (David Tribby)
Newsgroups: comp.sys.apple2
Subject: Re: rom disk
Message-ID: <54240025@hpindwa.cup.hp.com>
Date: 18 Dec 90 18:24:33 GMT
References: <16894@brahms.udel.edu>
Organization: HP Info Networks Div/Cupertino CA
Lines: 33

THROOP@GRIN1.BITNET ("Throop,Henry B") wrote...
>Scott Harris writes:
>[what is a rom disk?]
>
>Applied Engineering makes a RamKeeper card for the gs that goes into the
>momory expansion slot, where then you can plug one or two gs RAM cards into
>it.  It retains a portion of the cards' RAM as battery backed, so it stays
>when the power is turned off.  You can then boot from this like a normal
>drive.
>
>Technically, it is not a ROM disk, since, as you point out, ROM is not
>changable, and the card doesn't actually boot off its ROM.  However, to the
>gs, a ROMdisk simply refers to a non-volatile RAM disk that appears as a
>standard ProDOS volume.
>
I believe the ROM Disk in the slots configuration refers to memory that is
mapped to banks F0-F7. RAM cards add their memory just above the "fast" banks 
on the mother board. The high portion of that memory can be configured as a
RAM disk.

Do the RamKeeper and similar cards remap some of the RAM to banks F0-F7?
There's only 512K maximum available there...hardly enough for a boot-up
of a GS. When you want to boot off of this battery backed-up RAM do you
set the configuration to RAM Disk or ROM Disk?

The Octoram memory card has a special add-on card, ESP, that adds battery
backed-up RAM beginning in bank F0. It comes with 128K, and can be expanded
to a "full" 512K. It's possible to put ProDOS 8 on there and actually boot
up from the ROM disk. I don't recall any other true ROM card for the GS.

Apple hardware gurus...any corrections?

-- Dave Tribby