tag:blogger.com,1999:blog-6264947694886887540.post823107564209308759..comments2024-03-27T22:51:35.227-07:00Comments on Ken Shirriff's blog: Counting the transistors in the 8086 processor: it's harder than you might thinkKen Shirriffhttp://www.blogger.com/profile/08097301407311055124noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-6264947694886887540.post-52950778204918374322023-01-19T02:55:44.499-08:002023-01-19T02:55:44.499-08:00Amazing article. for me, the number of 29000 trans...Amazing article. for me, the number of 29000 transistor has a lot to do with advertising issues. you managed to really demystify the amount of transistors in the processor, effectively classifying their use. I've never seen this review before. Congratulations!!!Richardhttps://www.blogger.com/profile/16961829638621596618noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-27068385600023535522023-01-17T10:57:45.423-08:002023-01-17T10:57:45.423-08:00Re: the comments from TheEditor: https://www.blogg...Re: the comments from TheEditor: https://www.blogger.com/profile/00750939859695685490<br /><br />It'd be really amazing to see the equivalent reverse engineering of a T414 or T424 Transputer, largely because it was such a ground-breaking mass parallel-processing CPU from such an early point in the history of microprocessors. Analysing the quasi RISC / Bytecode / RPN execution engine, alongside the built-in hardware scheduler and multi-Megabit/s communications channels would reveal a lot (I guess) about the design choices they made.<br /><br />Disclosure: my 1989 undergraduate 3rd year project was done on the University of East Anglia Transputer Rack (9 x T424s I believe) in Occam 2 (the equivalent of a 9-core system). I thought we were on the verge of massive parallelism for the general public, but sadly, sequential, uniprocessor computing was already too dominant.Snialhttps://www.blogger.com/profile/18339375292327879363noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-82838186563019608112023-01-17T09:29:21.747-08:002023-01-17T09:29:21.747-08:00Ken,
I love your work !
Just sharing a simila...Ken,<br /> I love your work ! <br />Just sharing a similar perspective from someone on the chip design/production side..<br /><br />Anyway :-<br />We used the term 'physical transistors' for the actual transistors on the die. <br />Two counts were reported... connected (with contacts) and not connected (think gate array and ECO cells[for later changes by modifying metal only]) .... yield analysis stuff..<br /><br />Early roms/pla were diffusion, later many Roms had all the transistors present but used contact or metal to program. They were a bit bigger in area but this saved the cost of an increasingly expensive Gate mask when making rom code changes. It also saved a lot of processing time if wafers were 'banked' pre-contact, waiting for the inevitable rom changes..<br />on die Pla/Pal use almost disappeared by 130/90nm.. it made sense in some cases but synthesized logic was way quicker to implement , easier to floorplan and sometimes smaller area depending on function. Replacement of some ROMs with synthesized gates was also a growing trend. I found it made reversing quite a bit harder.<br /><br />The phrase "Logical transistors" (with apologies to analog designers) was the Equivalent reduced transistor count. Parallel reduction being used as you mention. Series reduction used for gate shorted stacked transistors. This was done in the old mainframe days for faster LVS, with suitable adjustments to L and W parameters. It seemed to have stuck around.<br /><br />Diodes were extracted and counted separately by type. Various diffusion diodes transistor diodes and gated diodes. Gated diodes sometimes used for interconnect antenna protection were actually transistors, only one connection to the signal wire.<br /><br />Marketing liked the big numbers for transistor counts. <br /><br />Then for logic alone there is the NAND gate or gate equivalent count, lots of ways to do that one.. transistors/4 is simplest. but physical or logical transistors.. And of course there are other ways to count logic gates..<br /><br />I am sure you are aware of similar chaos on reporting gate length Lgate, LDrawn, Lphysical, Leffective(electical),LMask, Lequivalent..and so on... <br />When someone quotes gate length, always good to know which one they mean.<br /><br /><br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-67462586411418179022023-01-16T08:29:11.970-08:002023-01-16T08:29:11.970-08:00> This allowed them to advertise their sets as ...> This allowed them to advertise their sets as a "10 transistor" radio, even though the actual circuit was no different than a 6 transistor radio. Fun stuff.<br /><br />To get halfway back to a "computer topic" I know of a similar cheat in the mid 80ies homecomputer market in Spain:<br />Amstrad installed an additional 8K RAM chip and some fake logic into their famous 464 model to bring it above 64K RAM (it became a "472" model). The reason wasn't marketing or competition but avoiding import taxes!<br /><br />See this video for details:<br />https://www.youtube.com/watch?v=_ErfWfjN9iU<br /><br />The chips were probably also rejects but who knows.Old Guyhttps://www.blogger.com/profile/04725508505561557922noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-66597780164102275792023-01-16T03:05:27.896-08:002023-01-16T03:05:27.896-08:00Great post as usual.
It looks like the area taken...Great post as usual.<br /><br />It looks like the area taken up by the microcode transistors / vacancies is quite small given the number of transistors in those parts of the die. Is it fair to say that there is much greater transistor density achieved there relative to the logic elsewhere on the die?Carlhttps://www.blogger.com/profile/08197616938972349223noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-5343652682684378572023-01-15T09:33:36.013-08:002023-01-15T09:33:36.013-08:00You counted all those transistors? Impressive! I...You counted all those transistors? Impressive! I'm reminded of the transistor count scandal involving portable transistor radios back in the 60's. At the time, small transistor radios pretty much all had similar performance. To distinguish them from their rivals, manufacturers would place their transistor count prominently on the front panel. "5 transistor", "8 transistor" etc.<br /><br />The transistor wars eventually heated up to the point that some manufacturers got the brilliant idea to bump their transistor count by placing transistors (typically QC rejects) on their PCB's that weren't actually connected to anything. This allowed them to advertise their sets as a "10 transistor" radio, even though the actual circuit was no different than a 6 transistor radio. Fun stuff.<br /><br />Ref.: https://www.antiqueradios.com/forums/viewtopic.php?f=4&t=338675Michelehttps://www.blogger.com/profile/11446439300213187649noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-14842254619801291302023-01-15T07:23:29.499-08:002023-01-15T07:23:29.499-08:00Hi Ken,
thank you for this detailed explanation ab...Hi Ken,<br />thank you for this detailed explanation about transistor counting. I'm looking forward for a browser simulator showing the enabled transistors like you did before. Do you think it is feasible or should be a daunting effort?Alanhttps://acassis.wordpress.comnoreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-35870044948150189142023-01-15T05:10:25.671-08:002023-01-15T05:10:25.671-08:00Thank you, Ken, for another excellent article. Thi...Thank you, Ken, for another excellent article. This particular one neatly sums up why I am a grateful subscriber to your work. The 8086 processor and the x86 architecture have run in parallel with the greater part of my life and I'm sure that has been for the better. Like most things, once they became commonplace, both the processor and the architecture, they became forgotten by most people but they deserve to be researched, remembered and recorded for posterity.Miceal Tyrenoreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-62685118931652623582023-01-14T14:39:54.600-08:002023-01-14T14:39:54.600-08:00No. Bristol based.No. Bristol based.The Editorhttps://www.blogger.com/profile/00750939859695685490noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-57545845659200600892023-01-14T13:31:51.274-08:002023-01-14T13:31:51.274-08:00Did you ever work in Colorado Springs?
Randy LeaDid you ever work in Colorado Springs?<br /><br />Randy LeaDogzillahttps://www.blogger.com/profile/03646509798175015025noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-1376036779268090652023-01-14T11:59:37.726-08:002023-01-14T11:59:37.726-08:00We (Inmos) tool pretty much the same approach when...We (Inmos) tool pretty much the same approach when we counted the transistors in the transputers (T414, T800, …). When I saw the article went through potential v. actual sites, high drive transistors implemented as multiple transistors, logical ROM bits v. actual ROM bits (the microcode ROM used rows split into two. If all the bits in one half of the row were identical then a decider truck allowed the half row to be omitted, saving space. I think this saved about 30% of ROM area. I can’t remember what we used when quoting transistor count. The Editorhttps://www.blogger.com/profile/00750939859695685490noreply@blogger.com