Re: Do it yourself upgrade: IIgs ROM 01?

[Patrick Schaefer <pa.schaefer@fz-juelich.de>]

David Empson wrote:

> I was not aware of any 28-pin 128Kx8 EPROMs.  To do this, the chip needs
> 27 pins just for power, ground, address (17) and data (8).  This leaves
> one pin for some combination of Vpp, chip select and output enable,
> which limits the usability of the chip and would complicate the
> programming algorithm.


28-pin 128k EPROMs are not available. Only mask ROMs have the DIP-28
pinout.

You'll need a 32 to 28 pin adaptor to use a 27C010 as the IIgs ROM.
These were common for the Atari ST TOS operating system upgrades. 

Patrick