Re: Son of ROM dumping - Congrats, Eirc! Message #5 Posted by Eric Smith on 26 Jan 2004, 5:13 p.m., in response to message #4 by Bill Wiese
Quote:
If a Spice somehow were to be rigged so as to allow execution of some test ML code (i.e, kinda a 'breakpoint dump'), figuring out the extra instructions may be a bit less hairy.
My thoughts exactly!
I've never figured out why HP tried the press-fit approach to assembling the Spice series. Originally I thought it was a form of cost reduction, but the more I've looked at it the less convinced I've become that it would have reduced manufacturing cost at all. Ken suggested that it might have been intended for better servicability rather than reduced manufacturing cost, but I don't think that makes sense either.
However, regardless of the reason, it does have the unintended benefit that it makes it a little easier for me to wire up my own ROMs to the calculator in place of the originals.
I can just pull the original ROMs, reassemble the calc, and clip on a set of probes to wire it to my hardware.
The probes have a tendency to want to fall off if the calculator is jiggled even slightly. I need to come up with a fixture to hold the top half of the calculator firmly in place (with the probes dangling out the bottom) so I can operate the keyboard and observe the display without knocking the probes loose.
If all else fails, I could solder wires in place, but I'd prefer to avoid that.
For those that are interested, although I can find NO published information on the third-generation internals, there are three published sources relating to the second generation (Woodstock, Topcat, 67, 10, and 19C):
- November 1976 HP Journal: two articles describe the processor architecture improvements over the first generation in general terms:
- U.S. Patent 4,177,520 contains what is, AFAIK, the only published source listing of any second generation microcode. It's a small chunk, but somewhat helpful.
- "An HP-67 Anatomy Lessson", a series of PPC Journal articles by Tom Napier, in which he describes partially reverse engineering the instruction set of the HP-67 in order to build a plotter interface:
- V5 N7 P7-8: Part IA, discusses hardware and bus structure
- V5 N8 P14-17: Part IB, discusses instruction set
- V5 N9 P6-7: Part II, more instruction set details
- V5 N10 P25-27: Part III
- V5 N10 P30: interfacing
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