- Sat, 2013-11-09 15:07
- 1 Comment
An Excellent write-up on the Programmable Logic Array (PLA) by Thomas 'skoe' Giesel. This PLA is found in the Commodore C-64 of the early 1980's and was the glue that held the video "VIC" chip, the microprocessor and the memory together to make a home computer.
Those familiar with the PLA know that just as it gave, it also took away and at one time was the single highest failing component due to poor passivation - the final step in chip production meant to protect the die. In section 4.3 Mr Giesel quotes Dam Morris that the failures were due to greater than 4% Boron in the Low Temp Oxide (probably activated further by the power density as these chips got a little toasty). He also goes to great length to discuss the geometric features of the chip and the differences in NMOS/HMOS processes.
Thomas did a great job in telling the story of a single chip, and I would say that almost every chip or piece of hardware or chuck of software has a story as well; the total story of a single C64 could fill a book. I am amazed at how the retro movements going on have revived some of the stories of the old days, sadly the players are taking their leave as time catches up.
Here the initials of one of the chip layout people: Joan Brenneke
Total PLA die:
Size differences between HMOSI and HMOSII processes
Block Diagram of the Input Cell