When did the 84-89 DME's start having the removable 24 pin chip?
 

I believe the earlier ones were soldered right to the boards, my 87 had a 24 pin receptacle the chip just pushed into. Ingo (who BTW did a FANTASTIC job, and quick!) just installed a 28 pin plug and stock program 28 pin chip in my DME and I have a 24 pin Autothority chip I want to give to someone. Obviously if he has a soldered on chip it wouldn't be worth it to de-solder/re-solder in this one as it's questionable if it will give him an improvement or not and going back to stock would be a PITA. Also, almost silly to have a 24 pin receptacle soldered in but certainly is one way to go for future upgradeability (though the 28 pin supposedly offers more programmability according to Ingo).. Soooo, anyone with an 84 chip it, and was it soldered?

I've seen an August of 84 Dated DME with the chip soldered on, so certainly some time after that. My 86 DME had a socket but with the 24 pins.

I believe all DME chips before MY 89(?) had 24 pins, now we know the 86 and later had a socket, wonder when that started? Sounds like his 84 would be soldered in if original...

Yeah mine was soldered - 84, swapped it out for the push in per Steve Wong.

I think it was 86 and up they started?

Bet Steve Wong knows! :D

My '84 (April build date, IIRC) has a socket.

Hmmm, guess it's still up in the air until my guy opens his up!

I never saw a soldered EPROM myself in a 911 DME. Soldered chips were common in the previous all-aluminum watertight DMEs for the 944. And these chips were actually ROMs without the E and P or PROMs. They had no quartz window. ROMs are mask-programmed and the information is part of the lithography. PROMs are one-time programmable (OTP) but can not be changed or erased later.

Soldering an EPROM to a PCB is somewhat uncommon since memory in EPROM version is more expensive due to the ceramic housing and the quartz window. That is what allows it to be erased and re-programmed.

These early boxes had the same 35-pin connector. Internally they used a different CPU and some very similar circuitry compared to the 911 DME. Their ignition stage was almost the same, and so was the fuel driver part. However, the flywheel decoder was built discrete with comparators where the 911 has another custom chip doing this.

But that doesn't mean there weren't soldered versions for the 911 DME. What I do know is that the first 911 DME had only a 2k 2716 EPROM . Later the size changed to 2732 but the content was still only 2k. The "rest" of the code resided on the CPU itself. It was a mask-programmed CPU that Intel made specifically for BOSCH. In the later DME the internal CPU memory is disabled and the entire code is on the EPROM. The EPROM size went to 2764 (8K).

Cheers,
Ingo