On Wed, 23 Sep 1998, Greg Dunn wrote:
> FYI, there are two modes in the original IIgs that you can set from the
> control panel; one is a compatibility mode that runs at 1 MHz, the other
> a 2.8 MHz accelerated mode that sometimes caused problems with peripheral

Even when in fast mode (somewhere around 2.8MHz, but some cycles were
stolen for DRAM refresh, so you only got around 2.5MHz), the CPU was
slowed down to 1MHz for I/O space accesses, so peripheral timing was
generally okay. I've never had a problem myself, nor do I know anyone who
has... I vaguely remember hearing about some card that wouldn't work
properly in fast mode though. The slow mode was mainly for running games
and stuff that would be too fast when accelerated.

> timings.  You can get accelerator cards that run much faster, but they
> don't muck with the bus speed.  I don't remember the serial ports
> behaving any better in the accelerated mode, though; and Appletalk
> worked even in the "slow" mode.

One of the popular accelerators, the ZipGS, had switches that determined
if it should slow down to 1MHz when accessing a certain slot. So, you
could set it so that accesses to the floppy drive controller, which was
highly timing-dependent, would slow down to 1MHz, while accesses to a SCSI
card would run at full speed.

ObNetBSD: ProDOS file system support would be kinda cool :) Although HFS
would be much better...