[vcf-midatlantic] Fake 7400-series memory

Herb Johnson hjohnson at retrotechnology.info
Thu Aug 24 11:04:44 EDT 2017


 > That was a rather interesting read. It's like a combination
 > of archeology and technology. - Joe Oprysko

Right. That's what early vintage computing looks like - kinda. ;) 
Editorial follows, for those interested. Otherwise: thanks for this 
glimpse into a corner of chip-collecting. - H

Doing some Web "archeology" found the originator of the decapitated 
chip. It's part of a recent project by Robert Baruch which he calls 
"Project 54/74" and hosted on YouTube and a wiki at project5474.org, and 
his Twitter account. He extracts chip die from original 7400 (and the 
industrial/military version 5400) logic chips, for annotation and 
imaging; then reverse engineers the schematic. He seems to be doing 
other vintage-computing stuff as well, with new S-100 boards and 3D 
printing, very 21st century.

Tracing out chip-die sounds like rocket-science; but it's a matter of 
knowledge and tedium, recognizing visual patterns and following the 
likely logic. That's what the "fake" poster Ken Shirriff performed in 
his deconstruction Web post. TTL gate-level logic is usually described 
in 7400 documents, but not in detail. EE's in the 70's era (like me) 
were trained in semiconductors at almost the die level; the detailed 
knowledge is/was available in other textbooks for IC design specialists.

And, it's something done in the microprocessor collecting world; tracing 
out early CPU dies. There may well be other such projects, for other 
chips including TTL. And it was professionally done in the era as 
literal reverse-engineering; competitors looking for ways to produce 
copies, learn design techniques, and so on.

"Archeology and technology" overlap considerably; archeologists try to 
reverse engineer how structures or tools, homes, weapons were made. To 
me this is another example of what I call preservation by restoration 
and repair and Web publishing. I work at the S-100 board and chip level, 
not at the die level. As do others in this email list.

Herb Johnson

-- 
Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net



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