But I also have ZX80 and Jupiter Ace.......oh, I see what you mean.
That's who I am, that's what I do. Can't easily change that.

It's forth on a Jupiter Ace, Jim, but not as we know it.

If you haven't a PET, you can get your retro themed Halloween experience in online emulation here:

masswerk.at/pet/?prg=3d+...

(If you haven't a keyboard with a numpad, you can always use the onscreen keyboard for convenient maze navigation and monster dodging.)

Yes, that's about it for a fastload. The standard CBM80 header on a cart at $8000 which runs as normal, sets up the vectors then disables itself until a vector is triggered. Usually the vectors point into IO space which peeks through to the ROM to code which enables it again as required.

They aren't suitable for the project I bought them for, but maybe something in the future. Useful to keep many and varied dev boards around.

I think it is, but in testing, toggling an IO pin on an off with a "single cycle" instruction results in an 8MHz output, with a 64MHz clock.
On the AVR with the 24MHz clock, I get 12MHz.
(and yes, I could see the assembler was correctly generating a series of 1 cycle BSF and BCF instructions)

(and yes I know it's my fault for not reading the small print. I was very close to getting something working on a 24MHz AVR and just didn't have enough clock cycles, so I thought a 64MHz PIC for the same manufacturer would be an upgrade, not a downgrade. Oh well, back to the drawing board)

Also useful for testing. That's why I made these "joystick emulators".

The "Advanced Level" kit for the Mini PET was like that. Who needs legends on the keycaps or silkscreen on the PCB? That's for the amateurs.
blog.tynemouthsoftware.co.uk/2022/04/mini...

I vaguely remember using some miniature rivets to create through hole plating on a home etched double sided board many years ago. I think I only tried that once. Even now I try to use a few vias as possible, and in many cases none at all.

PIN 40 is VSync out, which when I got the board was doing nothing. Maybe they thought that was due to a short somewhere and wanted to isolate that pin?
(although the actual problem was the 154 failing and the resulting bus conflicts which stopped the bootup before the chip was initialised)