56 votes
Accepted

Zilog Z80 freezes while binary counting up to 65 536 (2^16)

There are many issues here. As it is already said in comments, decoupling capacitor is a must! 555 (non-CMOS) timer output is very much like the output of TTL ICs, however Z80 requires a firm logic ...
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  • 9,326
45 votes
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Why was 2^127 − 1 an interesting problem for "Baby"?

It's hard to know for sure with just that picture, but that's a Mersenne number and a prime one at that. When a mathematician writes a Mersenne number on a board they are not thinking about getting ...
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  • 2,195
44 votes
Accepted

Z80 CPU address lines not stable

It appears that A0 through A6 operate correctly, but A7 though A9 (I've not tested the rest of the upper bits) are only active on the clock edge. Doesn't that exactly look like refresh cycles? :)) ...
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  • 173k
31 votes

Why was 2^127 − 1 an interesting problem for "Baby"?

Update: It seems as if David Marshall has found the missing link: The footage used in the clip is not just from the Manchester Baby, but also from the Manchester Mark 1 which became operational ...
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  • 173k
28 votes

Do instruction exercisers exist for 8086 and 68K (and other) CPUs?

Throwing some things out there that might fit the bill: 6502: AllSuiteA which assembles into a single binary and exits, leaving a failure or success code in memory; 6502 and 65C02: Klaus Dormann's ...
16 votes
Accepted

Testing RAM on an OmniBook 300?

The Omnibook has its own self-test which can be run by pressing Esc when powering it up. The best freely-available general-purpose memory checker is PCMemTest; older versions of its predecessor, ...
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14 votes

Do instruction exercisers exist for 8086 and 68K (and other) CPUs?

I understand the question (now), as asking about self test programs to check a CPU (or its emulation) for correct operation by trying out certain instructions and verifying the results. Does this fit? ...
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  • 173k
14 votes

Zilog Z80 freezes while binary counting up to 65 536 (2^16)

I'd just like to expand on a couple of points in lvd's excellent answer. Reset Circuit You might get by with just using a jumper wire to short the reset pin to ground for a brief moment after you've ...
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12 votes

Do instruction exercisers exist for 8086 and 68K (and other) CPUs?

Toni Wilen (of WinUAE fame) has written a CPU tester especially for MC68000: https://eab.abime.net/showthread.php?t=98747
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  • 520
11 votes
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Testing/using a joystick in AppleSoft?

The paddles and joysticks on the Apple work by charging a capacitor through a variable resistance (potentiometer). For the first joystick, the X-axis corresponds to paddle 0, and the Y-axis to paddle ...
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  • 1,048
8 votes

Do instruction exercisers exist for 8086 and 68K (and other) CPUs?

The Modcomp minicomputers were shipped with extensive self-test programs (on nine-track magnetic tape, no less). These were stand-alone programs (no operating system needed) that tested everything ...
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  • 1,886
7 votes

BBC Master 65C102 co-processor — test memory

PAGE and HIMEM are what you might call "system variables" in BBC basics, they mark the bottom top of the memory available for Basic use, they are intiialised from OS-provided values but can be changed ...
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  • 1,939
6 votes
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What is the proper way to test the PSU output for a Commodore 128D?

WARNING: Electricity is dangerous. Don't open up your computer without turning off the power and allowing the capacitors to discharge. If you need these instructions for anything other than knowing ...
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5 votes
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How to test an Orange Micro Grappler+ card?

Issue A is probably just the card waiting to detect a printer. (But I haven't disassembled the ROM.) Issue B is probably because you're trying to connect a serial printer to a (Centronics) parallel ...
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5 votes

BBC Master 65C102 co-processor — test memory

The 64KB of RAM for the 65C102 co-processor is provided by eight MB8264 64k x 1-bit chips. Each chip provides one bit of memory for every address, meaning that all eight chips are used for every ...
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  • 7,664
3 votes

CDTV Diagrom 1.2 Extended Memory Test AddressError Detected

In the DiagROM "AddressError Detected" is displayed when the CPU enters exception vector #2 at address $0000000C. This occurs if a word or longword access is attempted at an odd address, ...
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