YAY! Found the latest TDL ZPU board problem

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Terry Fox

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Dec 23, 2025, 12:12:42 AM12/23/25
to Altair 8800
So, I've been going over Walt's TDL ZPU board some more.  It turns out there was a hairline solder bridge between two address lines on the Z80 socket.  I removed that, and cleaned up some ugly solder resin between the pins, and the board is now working.  I had previously resoldered all the Z80 pins, but apparently missed seeing this short.

It's funny, because last night I took the time to single-step the initial AMON boot through about 30 or steps on both the Cromemco ZPU and the TDL ZPU, they were pretty much in lockstep.  So it must have been a pair of addresses that aren't involved in those first 30 or so instructions.

Time to clean the board up a little more, and run it for a few days.  It runs AMON fine, and boots CP/M 2.2 from the serial server.
Terry

Joseph Corda

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Dec 23, 2025, 12:14:52 AM12/23/25
to Terry Fox, Altair 8800
Great News Terry !

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Walt Perko

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Dec 23, 2025, 12:18:59 AM12/23/25
to Altair 8800
Hi, 

Wow Great!   I hope that's the last fix for the computer.  

So is that the 9-Slot Backplane, mini-Front Panel, TDL ZPU, FDC+, 88-2SIOJP, 88-2SIOR1 all working together?  I think I had the 88-2SIOR1 addressed as 14h/15h & 16h/17h for utility stuff (Servo Motors, Stepper Motors and a Speech System.)  .  


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