From searching the DIY stickies, it looks like the uc in the ECU is a 6811 or some derivative thereof. Now the 6811 was first introduced in '85. So did GM get an early version of it and develop the ECU around it? Did GM start using the 6811 later and embed another controller before using the 6811?

 

They are custom designs specifically for GM. In the C3 series of ECMs it is known as the GMCM (General Motors Custom Microprocessor). It was similar to the Motorola 6800/6803.

The P4 ECMs of that time used a microprocessor that was similar to the 68HC11. But again, was custom to what GM wanted/required. With the numbers that they were purchasing, getting a chip customized to their requirements is a given.

At the same time, several other chips were developed specifically to handle the various features. Such as having counter/timers for injection and spark/dwell timing. Along with pulse accumulation and PWM outputs.

RBob.

 

then, in my own words, the GMCM is a derivative of the 6800 (due to the instruction set similarity), probably licensed from Motorola? They were the ones used in the CCC of the early 80's? The P4's were probably a step up - analogous to the 8080 to 8085 intel processors of the same time, both 8 bit, but the 8085 much more versatile. Man i wish i was working in detroit on this stuff at that time. Truly cutting edge.

 

Umm, not in your own words, but in the words of the engineers that did the work (along with what I already posted). And not licensed from Motorola, but purchased directly from them. They did the re-design and the fab work for GM.

Figure that GM was purchasing likely 3 to 4 million chips a year, would you give them what they wanted? I would...

RBob.

 

I see. It was a customized version for GM. So to close this out, did GM ever go to a 16-bit or bigger controller? If so, do you happen to know the time frame and what processor it was based on?

 

I don't know if GM ever went to 16 bit CPUs. Or that they just jumped past them to 32 bit. Which occurred, IIRC, sometime in the late '90s. A variant of the 68300 may be what was used.

RBob.