5 ms·
I don't think it's a software issue -- AIUI the issue is that foundries will only let you use blocks for which the process was tested, or the yields would be un
by frabert 2y ago
I don't think it's a software issue -- AIUI the issue is that foundries will only let you use blocks for which the process was tested, or the yields would be unreliable/all over the place
- quotemstr 2y agoReally? I can't just call TSMC and say "Hey. Here's a mask. Please print 10,000, thanks."?
- morphle 2y agono, the mask must be made within the tight rules of the proprietary (and very secret) PDK of the TSMC Fab for that node. Just getting it certified that it fits the rules will cost millions. https://en.wikipedia.org/wiki/Process_design_kit https://en.wikipedia.org/wiki/Process_design_kit
- quotemstr 2y agoAre all fabs like this?
- hansihe 2y agoIt's probably more of a node thing than a fab thing. You would have a much easier time getting the fab to do random stuff for you on a legacy node compared to a leading edge node. Leading edge nodes are basically black magic and are right on the edge of working vs producing broken chips. You as a customer would never want to be in a position where you are solely responsible for yields.
- morphle 2y agoThere are only a few Fabs with nodes smaller than 28nm. Yes, all fabs are like that, with exception of a few experimental tiny labs at research institutes or universities.
- crote 2y agoThere are open-source PDKs[0] for education, research, and R&D - but they extremely rare and decades behind state-of-the-art. Nobody wants to give away trade secrets, so everything remains proprietary and behind an NDA until it has become completely obsolete. [0]: https://www.skywatertechnology.com/sky130-open-source-pdk/ https://www.skywatertechnology.com/sky130-open-source-pdk/
- amelius 2y agoInteresting. What is the granularity? Is it logic gates, or transistors?
- morphle 2y agothe granularity is at all levels: standard cells (=gates), transistor shapes, metal layer shapes down to groups of atoms (for quantum dots).
- shrubble 2y agoHow were the Parallax Propeller guys able to do it? They have a Propeller2 that is in either 40nm or 28nm, IIRC.
- RF_Savage 2y agoBecause those are now trailing edge nodes, so cheaper and easier entry for everybody.
- amelius 2y agoMaybe in reality it is somewhere in-between, where TSMC says: here is a set of standard cells that we tested; you can use them but if you modify anything then it's at your own risk.
- morphle 2y agoMaybe in therory, yes. In practise the fab will never allow you to do anything at your own risk because it might contaminate or break their $170 million machine. If you offer a few billion extra to cover that risk, your cheaper off building your own fab instead.
- amelius 2y agoI'm not convinced that moving transistors around freely would break the machine. How could that possibly happen?
- morphle 2y agoGoing outside of the PDK rules you risk contamination because a chip machine is a high speed ultra-accurate automated mechanical and chemical laboratory. It sprays extremely corrosive acids and vaporizes metals. Going a nanometer outside of the rules would send droplet or flakes of chemicals flying around at high speed. https://www.epfl.ch/research/facilities/cmi/equipment/photolithography/asml-pas-5500-350c/ https://www.epfl.ch/research/facilities/cmi/equipment/photol...
- haneefmubarak 2y agoThink of it less like moving transistors around and more like moving small groups of atoms around (also, you can get single transistor cells for analog and power designs). The processes required to place the rough groups of atoms in roughly specific places involves extreme amounts of energy relative to the size of what you are working with, which is supplied in a combination of chemical, radiation, and thermal forms. As a result, predicting what additional effects attempting to form specific micro-shapes might have is nontrivial. They extensively simulate and then carefully test all of their approved cells on an ongoing basis. Deviating from this could cause unknown issues, including damage, but doing the necessary work to prequalify your custom cells would be prohibitively expensive for most applications. NB: this is obviously a simplified explanation.