Re: TransWarp IIgs GAL's - Upgrade now possible

[Eric Smith <eric@brouhaha.com>]

Henry wrote:
> I know my cards are 50 MHz speed FPGA.  Probably all that is needed to run 
> at 8 MHz reliably.  I do have all the tools for the surface mount operation, 

Mine has the -70 part, IIRC, and is running find at 12.5 MHz (configured
that way when I bought it secondhand).  For reasons I stated earlier, it
is unclear whether this depends on the FPGA actually having better
performance than its specifications.

> but finding just one or two of the FPGA might prove to be a head ache.

Yes, very much so.  They also tend to be very expensive.

A new Xilinx XC2S15 has much more logic capacity than the original part,
and costs about $10 in small quantities.  Unfortunately it is not
available in the same PLCC package.  Worse yet, without the source code
(or schematics) for the original FPGA configuration, it is not possible
to generate an equivalent FPGA configuration for the new part.

This would be a fun reverse-engineering project, if only I had the time
to spare.  But it is quite possible that designing a new IIgs accelerator
from the ground up would take less time than reverse-engineering the
TWGS FGPA configuration.