They are quite useful to put under the legs of a table that needs leveling up.

Thanks for the links, interesting to see the reverse engineering of Sinclair's calc, amazing what you can do in 320 bytes. I remember my uncle building the kit of the first model, it was like a miracle back then.
The calculators started with the 4001 & busicom, then eventually TI went back to the ...

The chip in the 1974 advert is the 2529. Now if that chip has the same bug I found in the 7561, then its likely to be the same CPU/code. So if anyone has a calculator based on that chip, type:
[1] [EE] [1] [0] [-] [1] [=] displays 1 exp 00!
If that bug is not there, the chips *may* have different ...

Its a fair point. I do have a few of the old calcs, but they are working, so I was a bit reluctant to destroy them. I have decapped a ceramic chip before, but not a plastic one. Is the die embedded in the plastic?
Was an LCD version of the p50 or SR4912 produced? I only have seen LED versions, and ...

So there is this thread on Lemon64 about hacking the old CBM Calculators:

https://www.lemon64.com/forum/viewtopic.php?t=84313

After the discussion about the 6500/1 here, I believe the 7561 MCU is likely to be similar, but I would like to hear what people here think. As discussed in this thread, it ...

The 6500/1 is an interesting early device.

On a tangent, there is this piece on hacking the 6500/1 in the CBM VC1520 printer:

https://e4aws.silverdr.com/hacks/6500_1/

Extracting the code from the device, a complete IEC interface and print controller and chr set, implemented in 2048 bytes of Rom ...

I did see a really old ad in BYTE for a 6502 version of Small C for the KIM on Paper tape!

I remember tinkering around with Super C for the c64 or c128, I did benchmark it, now cant remember the results! I think it was comparable to Abacus Basic64/128, which was one of the better basic compilers ...

I was thinking, would a "true" PET emulator be possible for the c64/+4? I wrote a simple Basic one back when i got the 64, that sets the screen to $8000 and Basic to $0401, etc, so most old PET programs could run with just the odd mod.

But what I mean is switching to 64k Ram mode, then loading an ...

Yes, you are right, forgot about rs232, although I built the Maplin userport level converter kit back in the day. Hardly ever used on CBMs since its software driven, 5 volt only, CPU intensive and very slow. 2400 baud was unreliable on the c64 because of NMI conflicts with VIC2 "bad lines", unless ...

Thats interesting, thanks. So this problem shouldn't occur with the CBM machines as they dont use NMIs in the normal OS.
Perhaps the C128 problem above is caused by some other bug? For example, I recall there is some problem using decimal mode on the v20, because the IRQ rom routine doesn't handle ...

It should be possible to test this? If you have a very tight loop around a BRK and a very fast (VIA driven?) IRQ timer running, say on a vic20/c64/c128/pet, you could set up a situation where IRQs and BRKs overlap, and monitor the results by some method.

Interesting. So for the various built in or loaded Supermons that do single step with BRK, could these all be corrected by adding some code in the IRQ routine?
I guess with AttackUfo the machine wasnt using the IRQ for anything else so BRK is not too slow used that way?
But in a C64 you have the ...

I was thinking about the code for the AttackUfo game (6502+pre Vic20 6560).

https://sleepingelephant.com/ipw-web/bulletin/bb/viewtopic.php?t=8775

The game code uses the BRK as a JSR shortcut, with parameters inline after. Its probably some sort of compiled code.
I understand the early NMOS ...

Ok, another "Draughts" release, not exactly 6502 related, but you can see the progression in this thread from an 8k 1981 PET program (Orac) to a win32 program with 6 piece "perfect play" endgame database with 30 billion positions!

sage-screen1.png

Sage Draughts is a very comprehensive Draughts ...

Yes, but with the current code you hit a key to stop, edit, then restart with ENTER, which is a nice feature for such a small program. Really if you make a quarter char pixel version, you break the "small code" because of look ups to handle that at speed, so you might as add code for edit, proper ...