[ischmitz]

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