IIgs ROM1 Adapter

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Revision as of 01:42, 13 September 2018 by RMHenry (talk | contribs) (History)
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Apple IIgs ROM1 Adapter
Current version from ReActiveMicro

The IIgs ROM1 Adapter converts a ROM0 IIgs to a ROM1 by replacing the ROM on the motherboard. It allows an older Apple IIgs system to run newer software like GS/OS. It's user installable, and removable in case the IIgs needs to be downgraded. And unlike other solutions, this one does not block Slot 3 when using a ZIP-GSX or TransWarp GS.

The Adapter project was conceived of and created by Henry from ReActiveMicro.

Project Status: Complete. In production. Actively sold by ReActiveMicro.

Support: Post on the Discussion page (link above) or email ReActiveMicro Support.

Sales: Visit the ReActiveMicro Store.


Back in 2005 when Henry from ReActiveMicro first returned to the Apple II he found several IIgs systems obtained were ROM0 and couldn't run GS/OS v6.0.1. He also found that some ROM0 IIgs users wanted to upgrade their systems to ROM1. However there isn’t a simple way to do so since Apple used a nonstandard ROM. Henry then found a way to use two Machine Pin Sockets to allow a 27C1001 EPROM to work in place of Apple’s 531000 OTP ROM IC.

Two projects came from this research. One adapter allows for use of a more standard ROM to replace the ROM on the IIgs motherboard. The other adapter allowed for reading the less common 531000 ROM. These adapters however were made from machined pin sockets which also lead to "socket stretch" of the IIgs motherboard socket when used. They also blocked Slot 3 when using a ZIP-GSX or TransWarp GS.

v2 of the project started on January 21st, 2016. It was technically a collaborative project with UltimateMicro2 and branded under the UM logo, and was the last before ReActiveMicro's full return back to the retro screen in mid-July 2016. The project was released for sale on March 10th, 2016.

v2 of the adapter saw several improvements. A Dip Plug was used which solved the issue of "socket stretch". The ROM was also changed from a 27C1001 DIP to a N28F010 PLCC Flash ROM. This had an advantage of also letting users develop their own firmware, however none used the adapter for this. The unit was still hand assembled, which was a bit cumbersome due to the size of the PCB and parts. There also was the issue of blocking Slot 3 when using a ZIP-GSX or TransWarp GS.