An IMSAI and an Altair walk into a bar...

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I was moving things around in the workshop today and decided to do a quick eval on two of the machines in my collection. You may recognize the IMSAI 8080 from the movie "Wargames". (note it's not THE IMSAI 8080, it's just AN IMSAI 8080). The Altair 8800 is a super basic model of that machine - it only has a four slot backplane (S-100 bus) and no floppy or tape boards. I'm not sure what it was originally used for. The original owner may have gone to a different platform instead of upgrading the Altair.

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5 май 2023

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Комментарии : 15

@mikepowell9316 Год назад

Love those blinking console lights. Thanks, Gene.

@EtheB1 Год назад

This reminds me very much of the Cincinnati Milacron CIP 2200B mini that I worked on in the early 70’s - step/reset/run 😎

@JoelReesonmars Год назад

Garbage in memory from startup looks like instructions to a processor with no illegal instruction exception. We used to toggle through the garbage like that on the one our industrial electronics teacher let us build in high school, until the teacher would tell us write something meaningful to toggle in. I would be looking up the opcodes in the opcode map to see if they were defined instructions when I could keep up. My lab partner dug up a lunar lander program.

@saccadecom Год назад

My guess is it's hitting a place with no memory, loading 0xFF which is the 8080 "Restart Interrupt 7". This forces a subroutine call to a location in low memory, which (if it's not initialized) sends it off into the weeds. If the low memory address is not present, it'll keep making the same RST7 subroutine call, with the return address stack eventually overwriting all of RAM.

@jeffnay6502 Год назад

I have a couple of videos that may help you do some really simple testing of your IMSAI and or your Altair that you might like.

@f15sim Год назад

Thanks Jeff. I've already gone through the Altair - it appears to be functional, but there does appear to be a nut loose in front of the front panel. ;) The IMSAI...has issues. I was working with it a bit on Tuesday and it's basically off to yeetsville. :) I need to pull it down to a minimum config and see if I can get it to start behaving. I'm quite sure I'll be watching your videos.

@jeffnay6502 Год назад

@@f15sim The good thing about making these videos, is that they remind us, how and what we were able to do with these old computer. When we get back around to playing with them again... Can't wait to see another video on these two machines. I have not played with mine for a while now. As I have been focused on growing fruits and veggies in my back yard.

@jeffnay6502 Год назад

Maybe you can manually load and run the Kill The Bit program on these two machines.

@jeffnay6502 Год назад

So, what happens when they walk into the bar???

@f15sim Год назад

They get a Senior Discount. 🤣

@jeffnay6502 Год назад

@@f15sim Definitely, they deserve it !!!

@PresidentialPudding Год назад

I don’t understand this much but it looks very complicated

@f15sim Год назад

They only appear complex - you can hold the entire architecture of these computers in your head, no matter how you configure them. Those days are long gone. The Altair 8800 (2nd machine in the video) was the first computer Microsoft wrote software for - in fact, Microsoft *exists* because of that computer.

@PresidentialPudding Год назад

@@f15sim wow