71B vs 75D

[Martin Hepperle]

In my view, the Capricorn CPU is remarkable technology and the 75 is an interesting bridge between the pocket calculators and the Series-80 desktop computers.

Unfortunately the RAM capability of the 75 is severely limited - the RAM also serves as a file system, like on the 71. They could have done better by adding an additional memory controller.

I think the CPU it is underestimated - one has to compare with CPUs like 8080, Z80, 6809, 6502 and the like.

For its time, the CPU offers some very innovative features, the only drawback in my view is that it did not provide multiplication and division op codes.

On the other hand, which CPU from this era gives you a large set of 16 and 64 bit registers and almost symmetric (all opcodes allowed with all registers) operations?

Similar features can be found later in the 68000 family.

You can extend the BASIC with new keywords or write "standalone programs" in assembler (these are in in principle BASIC keywords). This is no problem as in the Series-80 machines. Documentation is sparse, but the ROM listings and associated do0cuemntation contain all the information and together with the HP-85 Assembler ROM manual it is not really difficult, only time consuming.

Martin