3 ms·

yeah the 68k story is funny, I've heard that before, though I remembered it as Apollo that did that dual 68k trick. It always confused me why Motorola didn't j

yeah the 68k story is funny, I've heard that before, though I remembered it as Apollo that did that dual 68k trick. It always confused me why Motorola didn't just axe the original 68000 entirely when it released the 68010 (with the fix for the page fault mis-design). there was no reason to keep producing the former after the latter came out, and it couldn't have cost them any more to make the '010 and it was pin for pin compatible (I've stuffed an 010 in Atari STs here with 0 problems, for example).

kragen 3y ago
i think i was misremembering which company it was and you're right pin-for-pin compatible parts always have some differences: power consumption, setup and hold times, ground bounce, slew rates, noise margins, hysteresis on slow transitions, drive strength, stability in the face of capacitive output loads, endurance when subjected to overvoltage or overcurrent conditions, etc. dave jones of eevblog did a video a few years ago https://youtu.be/1VlKoR0ldIE https://youtu.be/1VlKoR0ldIE about how he shipped a bunch of defective μCurrent burden-voltage-eliminating current sensors. in his tests it worked fine, but many of his customers started reporting inaccurate readings. after sufficient debugging, he figured out that the problem happened only when its output was connected to a voltmeter with a high input capacitance, which caused its output to oscillate, introducing both noise and an offset into the readings. it turned out that one of the op-amps was going into oscillation because it couldn't handle driving that much output capacitance, a common problems with op-amps, but why was this never a problem before? he'd switched over to a second source that made a chip meeting the same specifications, but which turned out to be more vulnerable to output oscillations so, when you put a pin-compatible chip into a design in place of the original part, you have to carefully test the result to ensure that it still works properly. most times it will, but if it doesn't, you could have a product recall on your hands. worse, your customers may be incorporating your product into their own products if you pull chips without warning, for example when you start producing competitive chips, every company who designed them into a product has to suddenly switch over to their supposedly pin-compatible replacements. some of them will have their products fail unless they redesign them. they will have to pull their products from the market. everyone who designed a product incorporating your original chip gets fired, and when they finally manage to get a new job, they swear to never again use a part from your company and that's why lots of companies have been producing the μa741 and its clones like the lm741 since 01968, and why out of the 15522 different op-amps that digi-key lists as in stock, 1397 are listed as 'obsolete' and another 1042 are listed as 'last time buy'. and it's why a z80 you buy from zilog today still uses hundreds of milliamps i'm not an electrical engineer, i just play one on hn

kragen 3y ago

i think i was misremembering which company it was and you're right pin-for-pin compatible parts always have some differences: power consumption, setup and hold times, ground bounce, slew rates, noise margins, hysteresis on slow transitions, drive strength, stability in the face of capacitive output loads, endurance when subjected to overvoltage or overcurrent conditions, etc. dave jones of eevblog did a video a few years ago https://youtu.be/1VlKoR0ldIE https://youtu.be/1VlKoR0ldIE about how he shipped a bunch of defective μCurrent burden-voltage-eliminating current sensors. in his tests it worked fine, but many of his customers started reporting inaccurate readings. after sufficient debugging, he figured out that the problem happened only when its output was connected to a voltmeter with a high input capacitance, which caused its output to oscillate, introducing both noise and an offset into the readings. it turned out that one of the op-amps was going into oscillation because it couldn't handle driving that much output capacitance, a common problems with op-amps, but why was this never a problem before? he'd switched over to a second source that made a chip meeting the same specifications, but which turned out to be more vulnerable to output oscillations so, when you put a pin-compatible chip into a design in place of the original part, you have to carefully test the result to ensure that it still works properly. most times it will, but if it doesn't, you could have a product recall on your hands. worse, your customers may be incorporating your product into their own products if you pull chips without warning, for example when you start producing competitive chips, every company who designed them into a product has to suddenly switch over to their supposedly pin-compatible replacements. some of them will have their products fail unless they redesign them. they will have to pull their products from the market. everyone who designed a product incorporating your original chip gets fired, and when they finally manage to get a new job, they swear to never again use a part from your company and that's why lots of companies have been producing the μa741 and its clones like the lm741 since 01968, and why out of the 15522 different op-amps that digi-key lists as in stock, 1397 are listed as 'obsolete' and another 1042 are listed as 'last time buy'. and it's why a z80 you buy from zilog today still uses hundreds of milliamps i'm not an electrical engineer, i just play one on hn