This sounds great - EXCEPT - you will likely need an upgraded PSU to go with that computer once you have the new CPU card installed. Take it from someone who's had an A1200 with the otherwise excellent Microbiotics 030/50 + 32mb RAM - great card but you will have all sorts of weird, flaky problems without the upgraded PSU. Which means you will likely have to 'violate' the connector from either an A600, A500 or A1200 existing PSU - the actual power generation can come from a modified PC one correctly wired to that connector.
I also had an accelerated 030/50 A600 for some time and same deal.
The A500 PSU reportedly has a bit more oomph than the stock A600 or A1200 PSU, but it's still not enough.
great that he's doing this!
amigau
http://www.amigau.com
