Forum comments in chronological order

Anonymous
Wed 1-Oct-2025 02:52

What I have noticed with the source code of the Blackbird player is that LFT used illegal opcodes for it. It is probably because he wanted to optimize it as much as possible. I don't know if this is why you having problem with running it on SD2IEC but it is my guess.

Anonymous
Fri 24-Oct-2025 20:05

This is amazing, I might try programming one of my 88's like this and see if I can get it working!

Anonymous
Tue 28-Oct-2025 20:20

Puzzled by your "deposit" button. Normally I think this would be "load". I used to front-panel IPL many computers back in the 70's. Can't ever remember seeing a "deposit" button.

Anonymous
Tue 28-Oct-2025 22:05

Curiosity question: in practice do we know at which nanosecond within the VIC cycle when a VSP is triggered does the VIC assert BA, and how does this compare the when the RAS high to low transition occurs? The datasheet doesn'xt promise much about the BA timing (within first 300ns of half cycle). But if the BA transition is at least 40ns before RAS transition, it could be possible to do a hardware bugfix from an expansion port cartridge. The Ultimate II is already doing fraction-of-a-cycle address line manipulation to allow the cart rom to toggle itself in place of kernal ROM. Maybe it could do the same for VSP bugfix. BA, Phi0 are exposed on the expansion port. I am thinking a trick like the cartridge watches for BA dropping in the half-cycle following a write to D011, and immediately jumps in to help the VIC pull the address lines A4-A7 low. This can happen in non-VSP cases, but I think those will be DRAM refresh or idle cycles for the VIC so its pretty innocuous if we mess up the address read in those cases. But the trick could only work if BA moves quickly enough.

Anonymous
Wed 29-Oct-2025 07:17

That's because he's directly controlling the programming interface here, the panel isn't a memory monitor like the old mini-computers used. The "load" label is already used for loading the command and parameter bytes. Writing bytes to memory needed a second button and a distinct label, hence a synonym was used.

Anonymous
Wed 29-Oct-2025 08:07

PDP-8 and PDP-11 front panels have a "deposit" button to write a word to memory.

Anonymous
Wed 29-Oct-2025 13:13

Finally a use for the old ATmega128 circuits that were lying around. I saw that BS2 probably needs to be brought to its own button as well.

LEDs next to the data switches. A 100 ohm resistor and an LED between the data lines. And 10 kohms next to the LED legs. Then the switch's up/down pull works through 100 ohm + 10 kohm and when the switch is down, the LED lights up if the controller is controlling data.

Otherwise, there are enough ports on the top edge for more leds. As an extra, you could maybe even use an external IO port from the ones that are left.

Anonymous
Fri 31-Oct-2025 03:50

https://csdb.dk/release/?id=109000