Friday, 14 October 2016

PET 2001TEST for 6540/6550

I had some trouble with the 6540-ROMs in my PETs and built an special adapter to read them in my EPROM-burner.
But it's not possible to read them in my TL866, Merlin/Promenade C1 and the Tiny Eprommer :(
The 6540 need a clock to operate correctly!

I decided to code a test-kernel that verifies the 8-bit-checksums in the PET ;)
Also I appended a RAM-test for the whole 8kB.
You have to burn the image in an EPROM and plug it with an adapter in the H7-socket.
It also runs in a 2532-EPROM (upper half) in a 2316B-board in the H4-socket.

Download Image: 2001TEST V1.0

YouTube: 2001TEST in action ;)

The test reads the 8-bit-checksums (without carry) from the ROMs in H1 - H6.
It verifies the checksums with the romsets 6540-011 to 6540-026.
For testing the 6540-018 or 6540-026, just plug it in the H6-socket.
The ROM-test needs no RAM to run - only the screen-memory for visibility ;)

2001TEST also checks the RAMs with 55 / AA in a continous loop.
But it's not possible to recognize the I or J chip because the test needs 2047 bytes and there is only 1 byte space left ;)


  1. Great post thanks for sharing this great article keep posting such articles :)
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  2. This looks like exactly what I need. I'm trying to restore my Commodore PET that I purchased in 1978. At startup, it says 1023 BYTES FREE -- not 7167 as it's supposed to -- and people tell me that one or more of my RAM chips might be bad.

    I see that your download is a .bin file, but I don't know what to do with it now that I've saved it on my PC. Could you please give me more instructions?

  3. Hi, the bin-file is a 2k rom-Image. It will tell you what 1k-ram-pair is defective. I suppose it's I3,J3. You should Exchange I3 with I8 and J3 with J8 for testing.
    You have to burn the bin in an eprom and plug it with an adpater in the Kernal socket H7. You Need a Special Adapter for 6540 oder 2316 - depends on the board you have.

  4. Here you get Adapter boards:

  5. Is there a PET tester that I can load from Tape?