I am not sure if I will ever get to build the calculator but I am certainly going to read the article. Maybe a good project to develop some FPGA skills on, hmmm... Thanks for taking to time to scan and post Ken ----- Original Message ----- From: "Billy Pettit" <Billy.Pettit at wdc.com> To: <cctalk at classiccmp.org> Sent: Thursday, December 21, 2006 2:40 PM Subject: TTL Calculator Project Several months back, we talked about a calculator built from TTL. It came I had 7 requests for copies, which I mailed directly to the requestors. Apparently they disappeared into a black hole, because I didn't receive a single acknowledgement, let alone a thank you. So for those still interested, Al Kossow scanned my copy and posted it on bitsavers: http://www.bitsavers.org/pdf/practicalElectronics/digi-cal/Digi-Cal_Jul72-Ma y73.pdf Billy

I have originals of that.... It's interesting to compare that design with the HP9810 (either from the patent or from the schematics on hpmuseum.net). They're approximately contemporary (I think the 9810 came out in late 1971), they're both built The bigest difference is the architacutre. The Digi-Cal is a calculator in hardware. There's a multiplication counter. A BCD full-adder. And so on. The HP is really a computer. There's a general-purpose 16 bit processor in there (shich. OK, has a few BCD-related isntructions). Connected to it is RAM and DRO, the latter contains the programs to make it work as a calculator. And peripherals like the keyboard, display, and printer. That the HP is a general-purpose design is shown by the fact that the HP9810 (3-level stack RPN calculator), 9820 (algebraic-notation calculator) and 9830 (BASIC-programamble computer) are all essentially the same design and use the same processor boards. That, alas, is typical. -tony