Re: Convert RAM -> ROM disk?

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <1223.UUL1.3#25274@ace.com>, Luigi <luigi@ace.com> wrote:
> 
> Is there any way to change part of my RAM card into a ROM disk?
> I thought I saw part of a message once before that it was possible...

You might have seen a message I posted a while ago mentioning the
OctoRAM ESP, which is an optional card that can be connected to an
OctoRAM.  The ESP appears to be a ROM disk as far as the IIgs is
concerned, but it uses static RAM chips instead of ROM chips.  It has
a jumper to write protect the contents, and batteries to retain the
contents of the RAM while the computer is off.  The maximum size of the
ROM disk is 512k (minus about 512 bytes for the driver).

This card plugs into special connectors on the OctoRAM, so it cannot
be used with other memory cards.


It is not possible to set up a ROM disk using a RAM card that doesn't
provide support for this, because the IIgs firmware expects to find
the ROM disk driver in a certain memory location on the card
($F0/0000), and this is outside the memory area that the RAM on the
card will support.

Some RAM cards may have a special ROM on the card to provide the
driver, and allow some of the memory to be used as a ROM disk.  I
don't know of any such cards.

It wouldn't be much of a ROM disk unless it provided battery backup
and write protection (and remapped the memory out of the usual area,
if possible).

Assuming the card uses dynamic memory, battery backup would require
some complicated hardware along the lines of the Applied Engineering
RAMKeeper.