Date   : Fri, 19 Jun 2009 23:56:17 +0100
From   : jumbos.bazzar@... (Mark Haysman)
Subject: One ROM disabling all others on Bootup

Hi folks.

Working in a Model B, I need to be able to have the facility in a ROM, when 
necessary, to disable, and keep disabled, all other ROMs except itself and 
Basic, even through a <CTRL><BREAK>. I have a private memory flag outside 
normal memory that keeps a tag on if this is needed or not.

Currently, it works for any ROM that is in a lower priotiry socket, as my 
routine scans &2A1-&2B0, and unless it finds itself or Basic, it writes a 0 
in there as it's processing ROM call &03. Although I think it will still 
allow lower filing system ROMs to claim their memory workspace - I've not 
tested that yet - it certainly disables other ROMs in the system in lower 
positions.

However, this doesn't work for filing systems that are in a higher priority 
socket. I've tried claiming the &03 call, returning &00 in the Accumulator, 
but that doesn't seem to work.

Is there any magic way of doing this reliably, so that I can keep this one 
ROM, and Basic as the only active ROMs in the System, without any filing 
systems claiming their workspace?

Thx, Mark.