4 ms·
Two dies in one package: Teardown of a vintage ROM with double the storage
- kens 6y agoAuthor here if anyone has questions about vintage IBM integrated circuits :-)
- spaceribs 6y agoReally cool! I assume it would be possible to take the pictures you have, turn them into 1s and 0s via some sort of image processing, then pop out actual code?
- kens 6y agoYes, it would be straightforward to extract the data from these ROM images. (See the "Pulling Bits from ROM Silicon Die Images" article currently on the HN front page.) I extracted some of the data from the ROM, but it wasn't anything obvious. I didn't spend a lot of time examining the data since it's probably something like microcode for an undocumented IBM control processor. The extracted data did let me verify that the 9 bits were 8 + parity. To extract the bits, I made a simple JavaScript program where I click on the transistors. For a small amount of data, this is faster than performing image processing and setting up automated analysis software. One problem is that once you get the bits, there are a lot of uncertainties. Is a transistor a 0 or 1? What order are the bits in? Are the addresses left to right or right to left? So you end up with a bunch of cases you need to consider, rather than a nice hex file.
- trilinearnz 6y agoLiterally seeing the bits in your original article was a revelatory experience. Sometimes things are easier to understand when looking at earlier, historical technology. That linked article is also excellent. So exciting to see a visual analysis translate into a hexadecimal file!
- Stratoscope 6y agoYou may enjoy core memory, where you can see each bit (although not its state) with the naked eye. Here's a very pretty 4096 bit (64x64) core plane I bought a few years ago. The board measures 5" square: https://geary.smugmug.com/Computers/History/i-jb2rgF5/A https://geary.smugmug.com/Computers/History/i-jb2rgF5/A Core memory has the interesting property of destructive reads. You can write a bit directly, but you can't read one directly. Instead, you write the bit, and then a sense line tells you whether it changed or not. If your write-to-read changed the bit, then you issue another write to restore its original state. Here are a few of Ken's articles on core memory that explain that and much more: http://www.righto.com/2020/03/the-core-memory-inside-saturn-v-rockets.html http://www.righto.com/2020/03/the-core-memory-inside-saturn-... http://www.righto.com/2015/08/examining-core-memory-module-inside.html http://www.righto.com/2015/08/examining-core-memory-module-i... https://www.righto.com/2019/04/a-look-at-ibm-s360-core-memory-in-1960s.html https://www.righto.com/2019/04/a-look-at-ibm-s360-core-memor...
- spaceribs 6y agoyou left out the most interesting tidbit: these boards were hand stitched!
- trilinearnz 6y agoThat seems quite appropriate, given the loom-based origins of computing :)
- trilinearnz 6y agoLovely. Thank you for sharing these =)
- marcodiego 6y agoDoes the metal can packaging make the chip less vulnerable to static or fields? I mean, does it work somewhat like a Faraday cage?
- kens 6y agoI don't think the metal can makes much difference in this case, since it doesn't surround the bottom of the package. One IBM document says "A hard shell cover was used to provide rugged external structure for handling purposes. Many different metals or plastics would suffice for this purpose. A stamped aluminum cap was chosen." In contrast, op amps and other precision analog components were often packaged in round metal cans, but these enclosed the IC on all sides. Ref: Page B-8 of http://bitsavers.org/pdf/ibm/logic/SLT_Circuit_Design_Hbk.pdf http://bitsavers.org/pdf/ibm/logic/SLT_Circuit_Design_Hbk.pd...
- S_A_P 6y agoAdmitting total ignorance here how do seemingly the same components produce a capacitor and transistor. It just looks like different shapes of the same material. Why will one store electricity and another become a switch?
- zsmi 6y agoSee figure 6.5 on slide 5. http://web.engr.uky.edu/~elias/lectures/06_MOSFET_Operation.pdf http://web.engr.uky.edu/~elias/lectures/06_MOSFET_Operation.... About the only time one sees it these days is if someone is trying to match capacitance of a second fet for charge cancellation purposes. It's not a particularly area efficient way to make a capacitor in modern processes.
- kens 6y agoGood question. In a regular transistor, the gate does have capacitance but this is generally viewed as an inconvenient side-effect. For a capacitor, you make the gate much bigger so you get more capacitance. The other difference is that in a transistor you're connecting to both sides so you get a switch but the capacitor just connects to one side (handwaving a bit) so there's no switch action.
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