ClausB

It has 64K RAM. Congrats!

Congrats! May I suggest a DT-80 cart and a monichrome monitor? (Just don't let Mathy see that.)

I'll kick you too for doing that!

The mux chips are part of the keypad circuit and have nothing to do with the joystick pots. Always right means too much resistance from the horizontal pot, so, yes, broken wire or some bad connection to that pot, or even within the pot. Old pots go bad, like the crackly volume knob on an old radio.

In fact, it's a carry-over from the 1977 TI-58/59 programmable calculators. http://www.datamath.org/Sci/WEDGE/Modules.htm In high school I got a TI SR-56 programmable and loved it. In college I dumped it for a TI-59 with mag cards. Later in college I dumped that for a microcomputer. I looked at the TI-99/4 but it was too pricey. I got an Atari 400 and never looked back. Well, I did look back when the -4A went on sale cheap, but I passed it up. A few years ago I looked back again and got a beige one cheap on eBay.

Wow! Culture for nerds!

Yes, my main use of the Axlon was as a RAMdisk. Though I did also make a wireframe animation of 76 2K pages (see my avatar).

I homebrewed a 192K RAM in the day: https://atariage.com/forums/topic/122750-64k-atari-800/#comments

Yes, audio out. https://atarihq.com/danb/files/52analog.pdf

Cool project! In the day I built a less ambitious SIO network. At PDI, too much of my job was typing endless DATA statements of questions and answers for our Atari educational programs. Then I had to repeat it for our Apple and C64 versions. Instead I built a one-way serial network from the Atari to the others and transmitted the DATA statements. Increased job satisfaction! (I don't recall whether the Atari end was on the SIO port, an 850, or a joystick port. I do recall adding diodes and resistors to adapt to the other systems' serial ports.)

Funny. It was your ancient thread that led me to this. https://atariage.com/forums/topic/3345-atari-400800-demo/

https://youtu.be/xa-twkXhXDQ

FAFMUL is a replacement for the OS BCD FP multiplier and it's three times as fast. I'll wager it's the fastest BCD FP multiplier for the Atari. But it speeds up only multiplication (and, by extension, trig and log), not addition, subtraction, nor division. It's an OS patch, as in Rybags' 2nd category above.

Yes, good talk. Thanks for posting. I was at VCFE this year for the first time but the only talk I saw was Joe Decuir's. Great show. Curt's display was cool and I got to meet some fine Atarians. The museum was cool, including the radio telescope. They let us bounce our radio voices off the Moon!

Be glad you weren't limited to 16K - by a drill! http://www.sekperement.com/commodore-episode-446-inside-a-cbm-pet-4016-8-bit-computer-dave-bradley-2001-4032-6502/

Gave up on my ST, early enough that it still had some value on the used market. Just couldn't invest enough time and money into it as I did with the 8-bit.

I'll second that! I built a ZX-81 kit in 1982. Great little machine!

I wonder if this was a PDI title. Program Design, Inc. did some launch titles for Atari. Is there a "PDI" or something embedded in the listing?

Hate to admit it, but I still haven't connected a drive in years.

OK, I just had to upload it again. Yay.

If the AtMega can't, the Teensy ARM probably can. https://www.pjrc.com/teensy/

Yes.

Article on the differences: http://www.atarihq.com/danb/files/52analog.pdf

We discussed this a few years ago. I had figured out how to generate -COMMAND without adding extra hardware:

It was a pleasure to see Stephen again and to play with the cool new stuff he had on display. He had the best explanations and his enthusiasm was inspiring.