Do you remember when you received your first computer or device containing a processor with more than one main processing core on the chip? We think for many of you it was probably around 2005, and the processor is likely to be from the Intel Core Duo family of chips. With a dual-core ESP32 now costing relative pennies, it may be hard to figure out in 2020, but there was a time when a multi-core processor was indeed a really big deal.
What if we told you that there was another Intel dual-core processor in the 1970s, and some of you might have even owned one without ever realizing it? It’s a story that tells us [Chris Evans], about how a team of reverse engineering enthusiasts came together to unlock the secrets of the Intel 8271.
If you’ve never heard of the 8271, you can be forgiven, as far from being part of the chip giant’s processor lineup, it was more of a high-performance floppy controller that appeared on relatively few. of machines. An unexpected use of it came in the Acorn BBC Micro, where [Chris] met him for the first time. There is very little documentation on its internal functionality, so an impressive combination of stripping and research was required for the team before they could figure out its secrets.
As you might have guessed, what they found was not a general purpose application processor, but a mask-programmed dual-core microcontroller optimized for data rate and containing Programmable Logic Arrays (PLA). substantial. It’s a relatively large chip for its time, and with 22,000 transistors, it dwarfs the relatively svelte 6502 which does most of the BBC Micro’s work. Very hard work to decode RMO and PLA comes to the conclusion that the main core has some similarity to their 8048 architecture, and the dual-core design turns out to be a solution to the problem of calculating cyclic redundancy checks at the same time. fly on disk transfer speed. There is even another chip using the same silicon in the contemporary Intel lineup, the 8273 synchronous data link controller simply has a different ROM. Overall, the article provides a fascinating insight into this very unusual corner of 1970s microcomputer technology.
As longtime readers know, we are interested in reverse engineering of chips.