Re: Vulcan HD/PS???? & 8MB GS RAM cards

[spec@vax2.concordia.ca (Mitchell Spector)]

In article rubywand@swbell.net writes...

>     As Mitch, Nathan, and I have tried to say in one way or another,
>8MB setups must be regarded as somewhat experimental.

    Not quite, I never said that. All versions of the Apple IIgs will
recognize and use 8 megabytes of memory, there is no special trickery
involved beyond installing a board in the Memory Expansion Slot (8 MB
populated on the ROM 00/01 or 7 MB on the ROM 3). Software will still
run fine whether you have 512K or 8 MB installed in the system, the
machine was built to support that much memory without tricks.

    A problem is only going to arise *IF* your using devices which use
DMA (Direct Memory Access - a process in which the device can interact
directly with memory, bypassing the processor) and you have 5 megabytes
or more (4 MB is the DMA limit) present in the expansion slot. Such
devices can include SCSI or IDE controllers, video capture boards, etc.
The RamFAST SCSI does tricks to get around it, combined with certain 
designed memory boards, but it doesn't always work and risky IMHO.
(some have report success, others have reported failure). 

    Other issues that crop up with more than 4 MB in the expansion slot:
The ROM 00 only recognizes the first 4 megabytes when working with RAM
Disks (this was addressed in the ROM 01 firmware update). On the ROM 3,
if you have 8 MB of memory present, you cannot create any RAM Disk at
all due to a firmware bug. You can get around it by using System 6.0.1
however, so this was addressed too. Both these issues are kind of
moot these days since the ROM 00 hasn't been supported in years and
most people are using System 6.0.1 now (the ROM 3 can certainly run
it, even out of the box with not a single expansion board installed).

Mitchell Spector
spec@vax2.concordia.ca