13 Jun
2010
13 Jun
'10
10:32 a.m.
On 06/12/2010 05:55 AM, Steven Hirsch wrote:
For the IIGS, Apple developed a custom ASIC for
diskette I/O that I
believe could operate at a 2Mhz. clock.
Same "IWM" ASIC they used in the Apple IIc, Lisa 2, Mac, etc.
It can operate at 2 MHz, but not when running the same old RWTS code (or
the ProDOS or GS/OS equivalents). The IIgs slows to 1 MHz for 5.25-inch
disk access, same as the other models. Not sure about 3.5-inch disk
access. IIRC, the higher-speed choice on the IIgs is 2.8 MHz, but it is
forced to slow down to 1 MHz for bus access, including most of the
internal peripherals such as the IWM.
Eric