So what would you build with 74 series logic that runs at 1GHz...? - Page 1
Forum section: electronics / projects

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 21, 2013, 09:04:57 am
content: http://www.potatosemi.com/potatosemiweb/74Logic.html

author: calmtron
author_rank: Regular Contributor
timestamp: August 21, 2013, 09:15:37 am
content: What?! Crazy people ..Well, hmmm, maybe a frequency counter using a bunch of high-speed latches? Prescalers are for amateurs!

author: kayvee
author_rank: Regular Contributor
timestamp: August 21, 2013, 09:17:55 am
content: Gotta luv that name.... so errr cheesyIndeed, I see it made news in our local read all of 6 years ago.http://www.dataweek.co.za/news.aspx?pklNewsId=27186&pklCategoryID=36

author: EEVblog
author_rank: Unknown
timestamp: August 21, 2013, 09:22:14 am
content: They have been around for donkeys years now.Last I heard they ran it out of their garage.Always did want to test them, just because, well, you can.

author: calmtron
author_rank: Regular Contributor
timestamp: August 21, 2013, 09:22:31 am
content: Check out their front page athttp://www.potatosemi.com/- "Why called Potatosemi as Brand". The chinglish is strong with this one

author: EEVblog
author_rank: Unknown
timestamp: August 21, 2013, 09:35:43 am
content: Yep, still working out of their garage:https://maps.google.com.au/maps?q=6051+Prince+Drive.+San+Jose,+California+95129+U.S.A.&hl=en&sll=-33.796924,150.922433&sspn=1.752873,3.749084&hnear=6051+Prince+Dr,+San+Jose,+Santa+Clara,+California+95129,+United+States&t=m&z=17

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 21, 2013, 09:40:59 am
content: Quote from: EEVblog on August 21, 2013, 09:22:14 am..well they're easy enough to buy :http://stores.ebay.com/potatosemi_W0QQsspagenameZMEQ3aFQ3aSTQQtZkm

author: EEVblog
author_rank: Unknown
timestamp: August 21, 2013, 09:59:52 am
content: Quote from: wilfred on August 21, 2013, 09:51:53 amOnly if every load point is 2pF or less. Max frequency drops dramatically over that.

author: calmtron
author_rank: Regular Contributor
timestamp: August 21, 2013, 10:13:16 am
content: Wonder what the current consumption is when running at 1.25 GHz?

author: tinhead
author_rank: Super Contributor
timestamp: August 21, 2013, 10:20:23 am
content: Quoteeverything where you have need for. I've already used clock buffers, buffers, inverters and FFs.They works as expected, however is important to know that the PCB design is important as well when you wish go to the limits.A simple 500MHz frequenzy counter (without any special PCB tricks) is no problem with their FFs.Quote from: calmtron on August 21, 2013, 10:13:16 amspeed costs always current, at 1.25GHz you will have more issues with PCB and load!

author: nctnico
author_rank: Super Contributor
timestamp: August 21, 2013, 10:57:26 am
content: Quote from: mikeselectricstuff on August 21, 2013, 09:04:57 amThey could be useful for building your own logic analyser with GHz samplerate... The PCB design would be challenging though.

author: Rerouter
author_rank: Super Contributor
timestamp: August 21, 2013, 11:16:50 am
content: not to mention the input capacitance of one stage is too high to then feed into another chip without reducing the loading,while i'm no expert at these things, would one not get away with a capacitor on the order of 1pF in series to lower the effective capacitance and some resistance to keep the bias in check?

author: EEVblog
author_rank: Unknown
timestamp: August 21, 2013, 11:42:59 am
content: Quote from: Rerouter on August 21, 2013, 11:16:50 amThe input capacitance of the NAND gate is so high at 4pF, you can't drive it from another gate at full speed. Your 1.125GHz drops to maybe 850MHz with a single gate load on an ideal PCB.

author: Skimask
author_rank: Super Contributor
timestamp: August 21, 2013, 11:55:38 am
content: A 1Ghz OISC...that'll effectively perform as well as, what, a 1Mhz 8080?

author: c4757p
author_rank: Super Contributor
timestamp: August 21, 2013, 12:36:56 pm
content: Quote from: calmtron on August 21, 2013, 09:15:37 amI'm planning on building a frequency counter... might try to get my hands on a few of these and see how fast I can get them...Hope they can count better than a potato.

author: amyk
author_rank: Super Contributor
timestamp: October 16, 2013, 12:47:26 pm
content: I just bumped into this while looking for fast logic and I must say it's one of theweirdestcompanies I've seen. Makes me hesitate to order from them when their eBay store doesn't actually have pictures of their parts (nor does most of the Internet, it seems...) Looks like they're based in Taiwan.Also this curious note in their datasheet suggests power consumption is going to be absolutely insane:Quote

author: dannyf
author_rank: Super Contributor
timestamp: October 16, 2013, 12:57:23 pm
content: Layout at 1Ghz would far exceed what an amaturer could do. As a matter of fact, not many pros can do that either.

author: madshaman
author_rank: Frequent Contributor
timestamp: October 16, 2013, 01:00:11 pm
content: Quote from: dannyf on October 16, 2013, 12:57:23 pmWhy, a 1Ghz signal spans 30cm or so, not exactly mm wave?

author: c4757p
author_rank: Super Contributor
timestamp: October 16, 2013, 01:04:04 pm
content: If their noise margins are decent, I suspect a somewhat advanced amateur could pull off getting them to work. Now, if you were to have your design tested for EMC, the guy doing the test would probably just laugh at you.... but it might work.

author: tszaboo
author_rank: Super Contributor
timestamp: October 17, 2013, 11:52:34 am
content: This chips would be nice for transit time ultrasonic flow metering. But geez. Building a product which has a critical component coming from a company named potato semiconductor? Not a chance.I guess, this is one of the companies which are made for someone to buy them.

author: TerraHertz
author_rank: Super Contributor
timestamp: October 18, 2013, 08:12:56 am
content: I always liked using the old 74HCU04 non-buffered inverters as linear amplifiers.Now here's the same thing, but a bit faster.http://www.potatosemi.com/potatosemiweb/datasheet/PO74GU04A.pdfIt's amusing that Potato Semi are using a HP 54120B scope for their waveform pics. I recognize the screen layout. Pics taken with standard camera, because there's no screen capture.

author: Stonent
author_rank: Super Contributor
timestamp: October 18, 2013, 08:23:49 am
content: I guess when you come down to it, most anything digital could be built with 74 series logic.I'd like to see someone make a fully working x86 chip out of through hole 74 series logic. Heck lest just make it easy, a z80, or 6502!Maybe Alan Yates would be up for the challenge? It's not a 555 but it's of a similar era.

author: westfw
author_rank: Super Contributor
timestamp: October 18, 2013, 08:44:54 am
content: At that speed, wires between parts become a bottleneck...QuoteFirst; not quite accurate. KL10 equivalent (BBN pager, too.) Built by Foonly, which was founded by some people who had done a similar project at Stanford ("Super-foonly", according to the article. There was an F1 and an F4 as well. There was supposed to be an F5.)I spent some time working on porting BBN TCP code to Foonly Tenex, back in the day...It probably wouldn't be very interesting with 1.25GHz TTL chips. First of all; long wires. Second, I'm pretty sure it was "TTL" in the sense of "Not ECL like the DEC", rather than "100% TTL chips." I suspect it had a bunch of 2901 bitslice chips in it, which had some fundamental flaws when it came to making them go very fast. Sigh.Also, a COTS x86 system apparently does a fine job at emulating a PDP10 at much faster than any actual hardware ever ran. "Systems Concepts" and "XKL" also both sold significantly faster (than KL10, but predating the zippy emulators, I think) PDP10 systems. No one cared much :-((some rumors had it that cisco Systems was originally founded to build PDP10 clones, but got distracted selling some networking stuff to raise cash. I don't know for sure. But after Len left cisco, he founded XKL and built the TOAD-1 (Ten On A Desk))

author: EEVblog
author_rank: Unknown
timestamp: October 18, 2013, 08:57:42 am
content: Quote from: westfw on October 18, 2013, 08:44:54 amAs I mentioned previously, you are screwed right out of the gate (no pun intended) before you even get to the layout. These gates can't even drive the input cap of another single gate at the full rated speed.

author: Unknown
author_rank: Unknown
timestamp: October 18, 2013, 09:38:39 am
content: Is there any logic family with a fan-out less than one at their intended frequency?

author: Whuffo
author_rank: Regular Contributor
timestamp: October 20, 2013, 11:07:45 am
content: I was thinking that a nice electric fireplace could be built using them. The logic would generate fire patterns to be projected on the rear of the fireplace, and the heat from all the overclocked chips would warm the room quite:palm:nicely.It'd be quite the challenge managing output loading, trace lengths, clock skew, etc. and making something minimally complex actually work using these parts.

author: JohnnyGringo
author_rank: Regular Contributor
timestamp: October 20, 2013, 11:21:47 am
content: Potato Chips!I want a bag!

author: jpb
author_rank: Super Contributor
timestamp: December 20, 2017, 06:25:04 pm
content: I've just come across potatosemi so came here to find out more and found this old thread.Are they still going strong?Are there any advantages to using their high frequency parts at more normal frequencies (e.g. 10 to 20 MHz) - e.g. reduced jitter?Looking at their spec sheets they seem to have very high theoretical frequencies but the propagation delay is close to more standard parts.The parts are expensive but for one-off hobbyist designs this isn't such a big deal (e.g. spending $6 inc postage on a dual flip-flop for reclocking is not too bad if you're only using one of them).

author: David Hess
author_rank: Super Contributor
timestamp: December 21, 2017, 12:17:31 am
content: Quote from: jpb on December 20, 2017, 06:25:04 pmMaybe but faster logic does not necessarily mean less jitter. Without differential inputs, power supply noise leads directly to jitter.QuoteI noticed the same thing and their speeds are comparable to AS and FAST logic when reasonable conditions are imposed.QuoteBut there are cheaper and better solutions in this case like ECL.

author: jpb
author_rank: Super Contributor
timestamp: December 21, 2017, 02:30:47 pm
content: Quote from: David Hess on December 21, 2017, 12:17:31 amThank you for your response.It seems that their main selling point (high frequency) is not nearly as useful as the headlines imply.ECL has attractive specs but sadly it seems to be past its hay day. There is very little choice for ECL components or else they are horrendously expensive and the power supply requirements are a bit of a pain unless you use PECL.I get the impression that there are only a few niche users of ECL and only ON semiconductor seems to produce it. Though I know that Tabor Electronics use it in their ARBs.Though perhaps this is just indicative of the fact that almost everything on a commercial level at least will be done with FPGAs and microprocessors - the logic chip market is probably confined to education and hobbyists.

author: amyk
author_rank: Super Contributor
timestamp: December 21, 2017, 05:37:59 pm
content: Someone "sampled" one of their parts a few months ago, so they do actually exist:https://hackaday.com/2017/04/30/afroman-makes-a-uhf-oscillator-from-a-potato/For the longest time I thought it was some sort of elaborate joke, likehttp://atomchip.com/

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 21, 2017, 05:41:30 pm
content: Those probably fill very niche markets? As the relatively high input capacitances make power consumption an issue at this frequency in a lot of applications.

author: whatsthegeek
author_rank: Contributor
timestamp: December 21, 2017, 06:06:26 pm
content: Maybe a discrete RISC CPU ? XD

author: rhb
author_rank: Super Contributor
timestamp: December 22, 2017, 01:34:18 am
content: A PO74G14A should make a good 0.8 nS rise time pulse generator using the W2AEW circuit in video #88. Very useful for checking cheap DSOs.I tried to do this with ECL many years ago and had my head handed to me on a platter for failing to grasp how much BW a sub nanosecond risetime required. And how careful you had to be about circuit layout.

author: KE5FX
author_rank: Super Contributor
timestamp: December 22, 2017, 02:04:25 am
content: Quote from: alm on October 18, 2013, 09:38:39 amSort of like the 'Davy Crockett' atomic bazooka, whose blast radius exceeded its range.Some people (and companies, and governments) have too much time and money on their hands...

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 22, 2017, 02:11:28 am
content: Maybe... make a Don Lancaster TV Typewriterhttps://en.wikipedia.org/wiki/TV_Typewriterand see how fast it can go on a Tek 1GHz analog scope like the 7104.http://w140.com/tekwiki/wiki/7104

author: David Hess
author_rank: Super Contributor
timestamp: December 22, 2017, 03:01:14 am
content: Quote from: jpb on December 21, 2017, 02:30:47 pmThat was my conclusion when I first ran across their products and studied the datasheets.QuoteECL, or common mode logic (CML) which is ECL without the output emitter followers, is used anyplace where the highest performance is required. It is found in other logic products like like line receivers and transmitters without being called out.QuoteFPGAs are not suitable for low jitter applications. Where low jitter is required, an FPGA with external low jitter reclocking logic might be used.Quote from: rhb on December 22, 2017, 01:34:18 amSearching for suitable fast logic for fast edge generation was how I first ran across the Potato Semiconductor products. It is worth noting that with the exception of ECL and CML, designers actually make an effort to slow edges down to prevent excessive ground and power bounce; this was a big problem with AS and FAST logic.FAST and AS are not bad, especially if a 50 ohm line driver like the 74x140 is used, but I concluded that LVC or ALVC, especially the 125/126 tri-state buffer, is the best option for this application unless you use ECL or CML because a tri-state buffer can operate as a open collector/drain output to either ground or power.QuoteEven with the best layout, the package parasitics become a serious limitation. The best designs either use a termination within the IC like CML (common mode logic) or disconnect the output from the transmission line using an external diode or transistor which is where a tri-state buffer would be especially useful.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 22, 2017, 03:12:33 am
content: Hm, sorry, I always thought CML stood for Current Mode Logichttps://en.wikipedia.org/wiki/Current-mode_logic

author: David Hess
author_rank: Super Contributor
timestamp: December 22, 2017, 03:40:24 am
content: Quote from: Alex Eisenhut on December 22, 2017, 03:12:33 amI guess that is right. For some reason I thought it was called common mode logic.

author: KE5FX
author_rank: Super Contributor
timestamp: December 22, 2017, 03:46:01 am
content: Quote from: David Hess on December 22, 2017, 03:01:14 amThat's a bit... overbroad.

author: David Hess
author_rank: Super Contributor
timestamp: December 22, 2017, 04:29:18 am
content: Quote from: KE5FX on December 22, 2017, 03:46:01 amI can make it broader. If single ended logic is used which encompass all saturated logic that I am aware of including TTL and CMOS, then it is not suitable for low jitter applications. This is simply because saturated singled ended logic despite having high noise immunity has no or very little power supply rejection so variation of the power and ground levels shift the switching thresholds. Below is an example of jitter in a single 74F00 TTL gate caused by modulation of the power and ground from a TTL counter chain. (1)With special effort, an FPGA or other programmable logic may be used for low jitter functions however other functions have to be segregated to another device defeating the purpose of using programmable logic for integration.Besides drawing constant power reducing power and ground bounce, ECL and CML use a separate internal or if exposed, external logic level reference for their differential input stages. Discrete ECL can sometimes be found in old designs like the sampling oscilloscope which produced the photograph below.(1) That is obviously not the output of the 74F00 gate itself; it is driving a pile of low jitter discrete ECL logic to produce a precision edge. The jitter is all from the 74F00 gate though because of poor operating conditions.

author: jpb
author_rank: Super Contributor
timestamp: December 22, 2017, 10:46:24 am
content: This has turned into a general discussion of fast logic which I've found very interesting to read.My background (before I morphed into a computer scientist) was in high frequency analogue (MMICs). The issue of parasitics was critical, when in the tens of GHz range just bonding discrete FETs becomes difficult because of the added source inductance. The rule of thumb we used to use for bond wires was nH/mm. (I like such memorable rules of thumb - the other one I remember which I think came from Donald Knuth is pi seconds = 1 nano century - useful for working out how long software might run for!)

author: Zero999
author_rank: Super Contributor
timestamp: December 22, 2017, 11:17:43 am
content: I don't see how these Potato ICs are any better than the 74AUC series.http://www.ti.com/lit/ds/symlink/sn74auc00.pdfhttp://www.potatosemi.com/potatosemiweb/datasheet/PO74G00A.pdfWhat a really high speed logic gate? Try the HMC843, which can work at up to 25GHz but don't ask the price.http://www.analog.com/media/en/technical-documentation/data-sheets/hmc843.pdf

author: rhb
author_rank: Super Contributor
timestamp: December 22, 2017, 03:20:17 pm
content: Clearly only for the well heeled hobbyist. $692.11 each at Digikey.

author: jpb
author_rank: Super Contributor
timestamp: December 22, 2017, 04:18:45 pm
content: Quote from: rhb on December 22, 2017, 03:20:17 pmI remember back in the mid 70s a hobby electronics magazine, I forget which one - perhaps practical electronics, published a year long project on building a calculator from discrete logic chips.Perhaps someone might try building a 25GHz version

author: Zero999
author_rank: Super Contributor
timestamp: December 22, 2017, 05:46:36 pm
content: I did say don't ask the price.If you want 25GHz, better use asynchronous logic, the wavelength is just under 12mm, so you'll have to take the phase shift into account, as it passes down the transmission lines. It will also need to be water cooled, as the power dissipation is 528mW per gate.

author: rhb
author_rank: Super Contributor
timestamp: December 22, 2017, 06:15:45 pm
content: I rather expect that actually buying that part is more difficult than merely paying for it. I bet if you ordered a few hundred someone would come around asking questions. It just screams ITAR.

author: Zero999
author_rank: Super Contributor
timestamp: December 23, 2017, 08:50:26 pm
content: Quote from: rhb on December 22, 2017, 06:15:45 pmActually I struggle to see the applications for such high speed discrete logic. Does anyone know what it could be used for?

author: rhb
author_rank: Super Contributor
timestamp: December 24, 2017, 12:26:26 am
content: A "Fat Boy" device requires setting off multiple explosive charges at *very* precise times. Look at the 1945 Alamogordo test photos. I'm sure that there are other applications, but that was the basis of my ITAR comment.

author: Zero999
author_rank: Super Contributor
timestamp: December 24, 2017, 12:40:08 am
content: Quote from: rhb on December 24, 2017, 12:26:26 amOh well, at least it's RoHS compliant.

author: texaspyro
author_rank: Super Contributor
timestamp: December 24, 2017, 02:47:03 am
content: Quote from: rhb on December 24, 2017, 12:26:26 amThey don't have to be all that precise compared to modern electronics... as Bunker Hunt once said "a nanosecond isn't what it used to be". With a little care and attention to detail power MOSFETs can do the job.

author: sdouble
author_rank: Frequent Contributor
timestamp: December 24, 2017, 04:59:47 am
content: "luckily", not that precise at all.Quote from: rhb on December 24, 2017, 12:26:26 am

author: BrianHG
author_rank: Super Contributor
timestamp: December 25, 2017, 04:14:55 am
content: Quote from: Hero999 on December 22, 2017, 11:17:43 amI still need faster. Anything which can work 100GHz range?

author: Zero999
author_rank: Super Contributor
timestamp: December 25, 2017, 04:24:45 pm
content: Quote from: BrianHG on December 25, 2017, 04:14:55 amWhat the heck are you doing?

author: RES
author_rank: Regular Contributor
timestamp: December 25, 2017, 06:51:45 pm
content: Quote from: BrianHG on December 25, 2017, 04:14:55 amAbstract: High-performance graphene field-effect transistors have been fabricated on epitaxial graphene synthesized on a two-inch SiC wafer, achieving a cutoff frequency of 100 GHz for a gate length of 240 nm. The high-frequency performance of these epitaxial graphene transistors not only shows the highest speed for any graphene devices up to date, but it also exceeds that of Si MOSFETs at the same gate length. The result confirms the high potential of graphene for advanced electronics applications, marking an important milestone for carbon electronics.https://arxiv.org/ftp/arxiv/papers/1002/1002.3845.pdf

author: Zero999
author_rank: Super Contributor
timestamp: December 26, 2017, 11:09:08 am
content: Quote from: RES on December 25, 2017, 06:51:45 pmSeems quite a long way off.Anyway, CMOS gates, capable of operating at multi GHz frequencies already exist and have been used in CPUs for the last 18 years now, so why is there no >1GHz CMOS glue logic? Because that would require driving low impedance transmission lines, on a PCB, which is much more difficult than another logic gate, on the same die, via an electrically short connection. Driving a low impedance, PCB trace, requires much larger, slower transistors, than another gate input.

author: KE5FX
author_rank: Super Contributor
timestamp: December 26, 2017, 09:14:02 pm
content: Quote from: RES on December 25, 2017, 06:51:45 pmOut of stock at DigiKey, as usual.

author: BrianHG
author_rank: Super Contributor
timestamp: December 26, 2017, 10:45:59 pm
content: Quote from: Hero999 on December 25, 2017, 04:24:45 pmEither brain washing or a gravity pump...

author: rsjsouza
author_rank: Super Contributor
timestamp: December 26, 2017, 11:08:57 pm
content: Quote from: BrianHG on December 25, 2017, 04:14:55 amThat would be difficult commercially. The faster I have ever seen are those automotive radars operating at 81GHzhttp://www.ti.com/product/AWR1642

author: TomS_
author_rank: Frequent Contributor
timestamp: December 27, 2017, 12:23:19 am
content: Quote from: Stonent on October 18, 2013, 08:23:49 amYou havent seen the Monster 6502 then? Its not 74 series logic, but its discrete.I built a clock using nothing but transistors (https://ornotblog.blogspot.com) to form NOR logic, and believe me, you have to be damn dedicated to the cause to build something like that - it took me 5 months of reasonably solid construction. 74 series logic may make it a tiny bit easier, but I suspect an X86 would be too mammoth of a task othersome some other nutter may have already done it.