I have always used ML / BASIC programs I wrote to do troubleshooting / burn-in testing, using loopback connectors to test external ports (on a par with the original IBM XT Diagnostics diskette). The programs could be simple or complex, depending on the situation. Sometimes I only burn-in test the area of repair. For example the serial port, with a loopback connector. If the problem was in the address decode circuitry, then I test all devices (memory, display, RS-232, printer, etc). If the repair required replacement of an IC or module, then I usually test for only one or two hours. If the problem is intermittent connections, then I test for 24 to 48 hours, at elevated temperature.
Of course if the uProcessor is not running, then the computer cannot be used to diagnose itself. In that case, if the uProcessor has a pin that can "tri-state" all output pins (the 80C85 does), then I used a test computer with a parallel port interface I designed that could exercise all the address, data and control pins by clipping onto the target computers uProcessor with a cable and test clip. The test program could also write and read from Memory / Port addresses to check the address decoding circuitry on the target computer. But that was decades ago now. I should re-make that interface board again for nostalgia sake. Back in those days, I frequently used my M100 as a test computer where I was working (CALMA, a CAD/CAM equipment manufacturer), repairing Data General mini computers, and Lexidata graphics computers mostly along with the peripherals. Discrete ALU based processor boards with ~150 74LS type IC's, core and dynamic memory, 9-track tape, video monitors, serial data terminals, etc. Fun times. Regards, Peter > ------------------------------ > > Message: 6 > Date: Fri, 9 Jul 2021 19:58:12 -0500 > From: "Jeffrey Birt" <[email protected]> > To: <[email protected]> > Subject: [M100] Burn in program > Message-ID: <[email protected]> > Content-Type: text/plain; charset="us-ascii" > > Hi all, > > Burn in test? I was just wondering what sort of program you guys like to > run > as a burn in test of a computer you have just repaired. I modified the M100 > test harness code so can run a continuous RAM test but that is not a really > useful test that everyone can use as it only works with the test harness. > > Maybe something in BASIC that just runs some calculations, displays things > on the LCD, etc. to test how stable the computer is when running for a few > hours. Any favorites? > > Thanks, > > Jeff Birt > >
