[HN Gopher] Germanium transistors: logic circuits in the IBM 140...
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Germanium transistors: logic circuits in the IBM 1401 computer
Author : parsecs
Score : 49 points
Date : 2021-03-03 18:17 UTC (4 hours ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| mathiasgredal wrote:
| From what i have read, with my limited understanding of
| chipmaking, it seems that UO2(Uranium dioxide) makes a great heat
| and radiation resistant semiconductor with better properties than
| silicon or germanium[1]. So how come we arent using that or
| exploring other materials for pushing the limits of computational
| power?
|
| [1]:
| https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.52...
| userbinator wrote:
| The mere mention of uranium is going to make the paranoid
| scared, and nuclear regulatory agencies raise much concern.
|
| Even "depleted" uranium is somewhat radioactive, and it's a
| toxic heavy metal.
| the8472 wrote:
| U238 is an alpha emitter. You'd probably get way more bitflips
| than non-radioactive semiconductors experience.
| philipkglass wrote:
| Probably a few factors:
|
| - Difficulty growing high quality crystals
|
| - All the process chemistry for building devices would be
| different
|
| - Toxicity/radioactivity
|
| The third one is IMO the least important. There are a lot of
| semiconductor materials that theoretically have properties
| comparable to or better than silicon for solar cells (as this
| paper suggests). But having a theoretically good band gap
| doesn't matter if the actual material as grown is full of
| deleterious defects. We're really good at growing near-perfect
| silicon crystals. We're not so good at growing perfect crystals
| of iron (II) sulfide, uranium dioxide, etc.
|
| Even if that could be solved, re-developing all the chemistry
| and tooling for fabricating dense logic/memory devices based on
| uranium dioxide instead of silicon would require an
| extraordinary investment of money and time. It could be
| comparable to or even more expensive than the transition to
| extreme ultraviolet lithography.
| omgJustTest wrote:
| Chemical scarcity should be in your list, and it is the
| reason silicon will remain for years to come, at least in
| electric domains.
| retrac wrote:
| Yep. I tried to ballpark the amount of polysilicon used to
| actually make ICs. Somewhere between 100,000 and 10 million
| tonnes a year, I figure. Those little dies are only 100 mg
| or so but we print them by the billions. Whether the real
| number is more to the high or low end of that, it's
| hopeless. As Wikipedia says "About 118 tonnes of germanium
| was produced in 2011 worldwide."
| myself248 wrote:
| Not specifically about the 1401, but where do you find the time
| to produce this volume of high-quality content that obviously
| takes a ton of work and research?
| kens wrote:
| The secret is to retire :-)
| gjvr wrote:
| Ken Shirriff, your blog is just awesome.
|
| What a wealth of material you have on righto.com!
|
| Blown away.
| kens wrote:
| Author here for your IBM 1401 questions :-)
| addaon wrote:
| How similar or different are the performance characteristics of
| the NPN-based and PNP-based gates? Assuming there's a
| meaningful difference, are there signs in the design anywhere
| where this was considered? Thinking of cases where complex
| logic is pushed to the NPN stages and the PNP stage is used for
| just an inverter, or similar patterns.
| kens wrote:
| That's an interesting question. Looking at the documentation
| the NPN card (CHWW) and the PNP card (CGWW) have different
| switching characteristics (NPN is faster on and slower off).
| But I haven't noticed any difference in usage patterns.
| Ccecil wrote:
| My memory...which is very hazy and limited on this topic...is
| that the Germanium based transistors have a VBE of .3v
| instead of silicon's VBE of .7v
|
| So in things like amplifiers it gives you less zero point
| crossover distortion. In digital I believe it lends to a
| faster switch time but I could be very wrong on this part.
|
| Germanium is much more rare so the cost is naturally
| higher...from what I know.
| yholio wrote:
| What's DEFL - Diode Emitter Follower Logic, suppose it's IBM's
| name for ECL? Do we have examples of these circuits being used
| in critical circuits in mainframes of the 60s?
|
| I can't imagine a logic circuit of that era that was
| technically capable of being clocked at 100Mhz, 30 years before
| these frequencies became the norm.
| kens wrote:
| I've looked, but I can't find anything more about DEFL. (The
| table says it was used in certain serial numbers of the core
| memory for the Stretch computer, so it seems rather obscure.)
|
| Based on the speed, it's plausible that it is a type of ECL,
| but I don't know where the diodes would fit in. IBM had other
| names such as current-steering logic for ECL.
|
| Keep in mind that the 10ns speed doesn't mean you can run at
| 100 Mhz, since there are likely to be multiple levels of
| logic, as well as other delays. But it's still pretty fast.
| bsder wrote:
| Is it possible this is DTL (Diode Transistor Logic) in IBM-
| speak?
| kens wrote:
| It's possible. IBM had several other types of diode-
| transistor logic including DDTL, SDTRL and CTDL. The
| emitter follower was more often used with ECL.
| chmaynard wrote:
| Off topic: I understand that William Shockley was interested in
| exploring germanium semiconductors, which may have been a
| contributing factor in the exodus of eight of his senior
| scientists and engineers to form Fairchild Semiconductor. Could
| you comment?
| jecel wrote:
| Thanks for yet another great article! I was wondering about the
| inductor connected to the collector but you already answered in
| the footnote.
| kitotik wrote:
| Neat!
|
| NOS germanium transistors are still highly sought after(and
| therefore expensive) for music gear such as guitar distortion
| pedals and pre-amps. They impart a lovely 'gooey' quality that
| modern transistors just can't do.
| highspeedbus wrote:
| Glad to see other people that enjoy building guitar pedals.
| That seems increasingly rare. There are some interesting read
| if you like electronics and guitars:
|
| https://www.analogman.com/fuzzface.htm
|
| http://www.geofex.com/article_folders/fuzzface/fftech.htm
|
| Another one
|
| https://jacquespedals.com/the-ac128-transistor/
|
| An excerpt:
|
| "EPILOGUE : When supply will dry...
|
| In a very close future, all stocks, including mine, of original
| germanium AC128 or any usable germanium transistor will dry.
|
| Forever.
|
| After this extinction, that only a few aficionados will notice,
| there will be no other possiblities to obtain THE original fuzz
| tone than a used Germanium fuzz box or a digital model."
| gkhartman wrote:
| Yep, I have a diy fuzz effect pedal around here somewhere that
| uses a matched pair of germanium transistors. An older
| electrical engineer gave me a box of them after I explained how
| sought after they were. He couldn't get his head around the
| idea that I would want to use them in a new project when new
| silicon transistors would be superior for many reasons.
| kens wrote:
| It seems like audio applications like to use old parts: how
| do germanium transistors compare with tubes?
| Ccecil wrote:
| Tubes are better since they have amplify with less "zero
| point crossover distortion". Silicon has .7v and Germanium
| has .3v Vbe so that is why people seek them.
|
| My understanding though is that it is something you can
| tune by adding biasing diodes but requires matching.
|
| I am not an expert...just something I remembered from
| school :)
|
| https://en.wikipedia.org/wiki/Crossover_distortion
|
| Edit: added Vbe
| billjings wrote:
| Depends on the use. For low distortion, tubes fare better
| because their operating point is more linear than any
| single transistor. Ge doesn't make a huge difference here
| iirc.
|
| Outside their operating point is another story. As said
| elsewhere, Ge has a smaller and less sharp drop than Si,
| which is worlds different for all sorts of clipping
| distortion applications. The classic example is the Fuzz
| Face, where the gentler clip made for a warmer sound. Think
| early Hendrix versus late Hendrix. But the transistors were
| so inconsistent and the circuit so sensitive to the gain
| that only one in fifty would sound good!
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