22 Dec
2012
22 Dec
'12
2:47 p.m.
Soory for the time in replying my ISP has been on the blink again...
Ill spill the beans. I had aspirations of turning it
into something
scientific. Rom swap or what have you. Naive I guess. Anyone want to
Good luck, you're goign to need it ;-)
The earlier 'Voyager' series machines contained 2 chips. One was the
processor and keyboard interface, called 'NUT'. The other contained
everything else -- ROM, RAM and Display Driver (and is called R2D2, I kid
you not). The processor is similar, but not identical, to that used in
the HP41 series, so at least the instruction set is known.
But, if you want to re-code the RO, then either you have to find a way of
making the ROM i nthe R2D2 chip invisible to the processor (which is not
trivial, given that the address and data is transered serially over the
same line (ISA) and that this singal is needed fro the otehr sections of
R2D2) or you haev to somehow rebuild the functions of the RAM and display
driver. Then you have to interface an EPROM or sinmialr to the Nut bus,
this is essetially the same as making a ROM box or MLDL unit for an HP41.
And finally you have to fit it all in the case.
-tony