Re: TED based motherboard

From: Anders Carlsson (
Date: 2007-03-28 00:45:48


Bil Herd on behalf of Jeri Ellsworth wrote:

> The two resistors on the chip mark it as a TED where the test mode pins
> were higher impedance than predicted by the chip designers and a strong
> electric field would freeze the counters.

Oh, those are resistors? With my limited electronical knowledge, I really
thought they were diodes too. In any case, they both are wired together
at pin 4. One ends at pin 15, one at pin 16. With my poor eyesight at the
tender age of 32, I can barely read out the rating.. FH 481? FM 481?

Bil writes that he added an 8-bit latch "8529 or something like that",
while I observe two chips named 8329, assumed to be RAM. Ethan suggested
that U4 should hold a 82S100 or similar.

I need to get access to an EPROM reader/burner to dump those chips
safely. The 2764:s I could read off a C64 cartridge with EPROM slots,
but I don't think I have anything to read the 27128.

> Hey Haynie, Russell, Ryan: This thing look familiar?"

If it entertains somebody, I uploaded a couple more, huge pictures: (218 kB) (234 kB) (219 kB) (201 kB)

Feel free to copy them, but rather not deep link in e.g. a forum, as
they're a bit on the heavy side.

Now only remains the question, how does a prototype board from inside
Commodore labs end up at a PET reseller in the deepest woods of Sweden?
Lying totally forgotten on a shelf, resting on the bottom half of a C64
breadbox no less. Seemingly lacking a few chips and one wire sticking
out from the cartridge port (perhaps that was part of the prototyping).


Anders Carlsson

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