Show HN: A nibble-oriented CPU in Verilog to build a scientific calculator (opens in new tab)

I was part of a group touring HP labs in the mid-1970s.

They showed us how they computed the key dimensions and typography with an (HP) minicomputer, then had it print out the commands for some kind of numerically controlled cutting machine on paper tapes using an old ASR33 teletype.

The cutting machine generated moulds for the injection moulding machines making the keys.

The keys are in two parts: light coloured digits and symbols and darker plastic forming the shape of the key itself and surrounding the lighter symbol plastic. As a result, they can be worn down but they can never wear out.

Yes probably. What model is it? I repair and restore old HP calculators. One thin about all the models from 1972 through the early 1980s that use a battery pack - do not power the calculator off the adaptor alone - these models used a working battery pack as part of the adaptor voltage "regulation" - if you power off the adaptor without the battery a much higher voltage will get into the calulator and can permanently damage it. If you dont have a working battery pack, the only way to test it is with a bench power supply set to a safe voltage. For many of these models I install a lithium battery system and USB-C charge port so we no longer have to mess around with old leaky batteries and HP's poor implementation for charging them. Some of the models that are like this are: 35, 45, 55, 65, 67, the 20-series (21, 22, 25 etc) and the 30-series (31E, 32E, 33E, 33C, 34C etc). After these, the "Pioneers" came out (11C, 15C etc) which dont use a power adaptor and are safe.

I didn't think it was that much, but I checked my receipt from 2017, and sure enough it was!

I have in my hand (I guess I like using that phase today), my father's original receipt for the HP-45 (it's with the box and manual). $299.00 in 1975, which is $1,850 today(!!!).

Relatively speaking, electronics are very, very cheap today compared to what they used to be. Still appreciate that my $30 CASIO does 90% of that the NumWorks can do, but I'm happy to support upstarts such as NumWorks.

I was not making a pun, though the terms of art in that area were clearly made to be puns. I was pointing out that the byte-size of a CPU is typically defined as its smallest addressable unit, so, I was confused to see a CPU using an architecture that works with half of that size; it does not make sense to me.

When did we stop spelling it "nybble"?

A byte is not always 8 bits on old machines, though it is standardised as 8 bits nowadays.

This is why network RFCs talk of "octets", to avoid the ambiguity. Octets are always 8 bits.

https://en.wikipedia.org/wiki/Octet_(computing)

That is false. A byte is the base grouping and a word is the native size for a given operation. Some architectures even expose multiple word sizes. (TBF the entire concept can be quite fuzzy depending on the implementation.)

I think you might be missing the attempt at humor.

Intel 8080 already had DAA, so it could add BCD numbers. Because there was no BCD subtraction, that had to be done by an indirect method, e.g. by doing a nines' complement before a BCD addition.

Zilog Z80 improved this, so that on it DAA could also be used after a subtraction, when it would correctly adjust the result for implementing BCD subtraction.

This was one of the Z80 improvements that were considered important at the time of its launch.

While I have never considered worthwhile to do BCD arithmetic instead of converting the decimal numbers to binary numbers, the DAA instruction on all Intel 8080 successors, including on IBM PC compatible computers, was very convenient for converting binary numbers to their ASCII character string hexadecimal representation, for printing or display purposes (because the decimal adjusting happens to add the correct ASCII offset between '0' ... '9' and 'A' ... 'F', so the conversion to ASCII can be done branchless).