I so miss dinking with these things, they were so cool because you could completely understand everything that happens from the power on to a C:\ prompt, it was all documented. If you bought a machine from IBM, you got the ROM BIOS listings and schematics. I wish I would have kept one old XT from the company I used to work for. Hijacking the ROM signature scan by populating an empty socket on a network card was brilliant. Good show, thanks for the nostalgia. I'm looking forward to more on this. Back then, I used the timer tick interrupt to modify the cursor on each tick. It was a sweeping horizontal bar that went up and down. There is a BIOS function for modifying the cursor. Calling it from an interrupt wasn't the most stable thing either, sometimes it would hang the machine.
There's absolutely no way an XT could emulator a C64. It's not much faster, and has inferior graphics and sound. You'd need at least a Pentium to emulate a C64.
@Anders Nielsen It is possible to install linux on old smartphone but could we add something like raspberry pi pico or ft232h and make it a raspberry pi alternative to some extent.
9:24 Sorry to ask a dumb question, but I don't understand how you can learn anything from a multimeter applied to address lines because surely the address bus has moved on once the machine has booted the main BIOS? Why would those two address lines still be active?
Actually a good question! My assumption there was that the card latches or at least buffers the address lines, and they’re not directly connected to the bus or maybe they’re hardwired for a specific ROM type. I was looking for any change at all but I didn’t see as much as a blip - basically: I was guessing at that point :)
@@AndersNielsenAA I was impressed how far you can get with solving a problem like that with just a multimeter. I recently read a piece in the Raspberry Pi RP2040 datasheet that says that a Pi Pico ($4 or so) can act as an eight channel digital signal analyzer at speeds of several tens of MHz so I think that is the way to go. It would need some protection from the 5V TTL logic levels in these old machines. It takes time though to get all these tools working together, ...
I try not to escalate too fast up the tool chain and choose the "right tool for the job" but when you can use a Pico as a logic analyzer and a Blue Pill as a scope, all you need is a passive adapter board and some reasonable probes... Actually, a lot of the time I just grab the scope because it already has the convenient probes attached.
Well, technically just a clunky single board computer :) Microcontroller usually implies CPU, RAM and ROM in one package. I wonder what a Pi Hat would look like for a PC motherboard :)
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I so miss dinking with these things, they were so cool because you could completely understand everything that happens from the power on to a C:\ prompt, it was all documented. If you bought a machine from IBM, you got the ROM BIOS listings and schematics. I wish I would have kept one old XT from the company I used to work for.
Hijacking the ROM signature scan by populating an empty socket on a network card was brilliant. Good show, thanks for the nostalgia. I'm looking forward to more on this.
Back then, I used the timer tick interrupt to modify the cursor on each tick. It was a sweeping horizontal bar that went up and down. There is a BIOS function for modifying the cursor. Calling it from an interrupt wasn't the most stable thing either, sometimes it would hang the machine.
Thanks for sharing!
Great video!
Maybe you can conbine the two projects by making a C64 emulator on a PC-XT-Compact flash adapter, so that it can run C64 games.
There's absolutely no way an XT could emulator a C64. It's not much faster, and has inferior graphics and sound. You'd need at least a Pentium to emulate a C64.
It has enough RAM and a VGA card so technically there is a way - very slooooooowly :D
@@AndersNielsenAA yeah, ok, 1 frame every 10s 😂
@Anders Nielsen It is possible to install linux on old smartphone but could we add something like raspberry pi pico or ft232h and make it a raspberry pi alternative to some extent.
@@parshvapatel8484 Eventually I’m sure we’ll get a serial port on there
9:24 Sorry to ask a dumb question, but I don't understand how you can learn anything from a multimeter applied to address lines because surely the address bus has moved on once the machine has booted the main BIOS? Why would those two address lines still be active?
Actually a good question!
My assumption there was that the card latches or at least buffers the address lines, and they’re not directly connected to the bus or maybe they’re hardwired for a specific ROM type.
I was looking for any change at all but I didn’t see as much as a blip - basically: I was guessing at that point :)
@@AndersNielsenAA I was impressed how far you can get with solving a problem like that with just a multimeter. I recently read a piece in the Raspberry Pi RP2040 datasheet that says that a Pi Pico ($4 or so) can act as an eight channel digital signal analyzer at speeds of several tens of MHz so I think that is the way to go. It would need some protection from the 5V TTL logic levels in these old machines. It takes time though to get all these tools working together, ...
I try not to escalate too fast up the tool chain and choose the "right tool for the job" but when you can use a Pico as a logic analyzer and a Blue Pill as a scope, all you need is a passive adapter board and some reasonable probes... Actually, a lot of the time I just grab the scope because it already has the convenient probes attached.
Any PC can be a microcontroller if you run custom BIOS
Well, technically just a clunky single board computer :) Microcontroller usually implies CPU, RAM and ROM in one package. I wonder what a Pi Hat would look like for a PC motherboard :)
@@AndersNielsenAA maybe call it macro controller ;)