fpga emulation of a 68000-based HP9816
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Author:  BigEd [ Mon Dec 23, 2013 1:58 pm ]
Post subject:  fpga emulation of a 68000-based HP9816

Olivier De Smet has a number of software emulations of HP calculators and computers, and also two or three FPGA emulations. This one has a new, small, and efficient 68k core with a GPL license:

First, the 68000 softcore
- tg68 don't do movep and chk ... needed
- ao68 too large (more than 40KB of microcode ...) I need the onboard ram for other things
- suska core too large (more than 6000 slices)

So I wrote mine :)
- not cycle exact core
- all illegal are ok,
- movep and chk ok,
- mul and div WAY faster
- 32 bits internal alu
- 16 bits external bus
- generally less cycle used
- seem to work up to 16 MHz and use around 3000 slices
still in debug ... pga-hp98x6

boot-03.jpg [ 237.23 KiB | Viewed 4874 times ]

The small basic program show that my softcore at 8 MHz is roughly a 11 MHz 68000 :)
(and with slow ram, with a 16Mhz internal wait state)

Author:  Garth [ Mon Dec 23, 2013 9:04 pm ]
Post subject:  Re: fpga emulation of a 68000-based HP9816

Olivier is one of a many amazing brains on the HP Museum forum which was recently moved to in its new phpBB format. The non-forum part of the website is . A few of these men have used programmable logic and microcontrollers to make HP-41 (my main interest there) calculator modules and transplant boards that dramatically increase the calculator's capabilities beyond what HP ever provided when the 41 was in production. I want to get Diego's NoV-64 module which gives a dramatic expansion of RAM and ROM (flash), and load into it several older module images plus Ángel Martin's new 41z module which gives it a native complex stack and oodles and oodles of complex-number functions all written in assembly for best performance (unlike the Advantage module which had some of its functions in user language) and his Sandmath module image. He also has a Sandmatrix and another one or two. Even the manuals are outstanding, which is uncommon today. The 41CL is a transplant board you can put in the earlier (Coconut) HP-41's to replace the original board. It does not have an actual Nut processor, but emulates it, with, I believe, a microcontroller, at up to 50 times the speed of the original. It is a true emulation that allows plugging in the older hardware modules (such as the time module, bar-code wand, HPIL, etc.), and comes with the ROM images of over 180 modules already installed. Doing a "who's who" of the HP Museum forum would take some time, and I'm sure I'd leave out someone important.

Author:  BigEd [ Sat Dec 28, 2013 10:29 am ]
Post subject:  Re: fpga emulation of a 68000-based HP9816

Very interesting! The CPU itself is documented at - it's a version of HP's NUT, constructed from public information, so there's no extra layer of emulation. Sources are available too (but it's not open-source) - see

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