Quick update on this thread. 5MHz T102: * working well * stock CPU, stock main ROM, stock RAM. No change to the ICs * changes are reduced to (1) change the oscillator (2) add a /2 clock circuit (3) apply a modification to the RAM chip select circuit. * serial port works as normal, printer port works as normal. Audio is 2x higher pitch.
What I have working now is a dedicated 5MHz T102. I have ordered a board that, if it works, will allow software control of either 2.5 or 5 MHz. I'll have to put up a page at Bitchin100 to document the findings. I've also taken a crack at a much simpler M100 5MHz mod where the main ROM and the stock M100 RAM are replaced by an adapter board using the main ROM socket. BTW, the original M100 main ROM is REALLY SLOW! in the documentation it is spec'd at 600nsec, whereas your typical 27C256 is 150nsec or faster. I have to assume that the T102 main ROM is suitably fast because I don't have to change it. I really like 2x faster....;) With regards to NEC and M10 - the stock RAM will be too slow. More thought there. T200 may be next on my list, actually.
