Groups | Search | Server Info | Login | Register
Groups > comp.arch.fpga > #38730
| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Newsgroups | sci.electronics.design, comp.arch.fpga |
| Subject | Re: fast divider? |
| Date | 2026-04-01 09:12 -0700 |
| Organization | A noiseless patient Spider |
| Message-ID | <26gqskthcr1qfvkm62qh6qjg7cb0ipg4bu@4ax.com> (permalink) |
| References | (7 earlier) <10qgb98$39jr5$1@dont-email.me> <6honskhhs9lpc60c05dcn16v9pooqe8udp@4ax.com> <10qi8er$3tkci$3@dont-email.me> <cnjpsk9ev6uphcdeoqhnoeu37vb5epovd9@4ax.com> <10qjcna$ad1m$1@dont-email.me> |
Cross-posted to 2 groups.
On Thu, 2 Apr 2026 02:13:38 +1100, Bill Sloman <bill.sloman@ieee.org> wrote: >On 1/04/2026 7:06 pm, john larkin wrote: >> On Wed, 1 Apr 2026 15:54:44 +1100, Bill Sloman <bill.sloman@ieee.org> >> wrote: >> >>> On 1/04/2026 2:14 am, john larkin wrote: >>>> On Tue, 31 Mar 2026 22:30:44 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote: >>>> >>>>> On 31/03/2026 8:40 pm, john larkin wrote: >>>>>> On Tue, 31 Mar 2026 16:35:49 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote: >>>>>> >>>>>>> On 31/03/2026 2:00 am, john larkin wrote: >>>>>>>> On Mon, 30 Mar 2026 16:42:12 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> On 30/03/2026 2:18 am, john larkin wrote: >>>>>>>>>> On Sun, 29 Mar 2026 15:52:53 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>>> On 29/03/2026 8:38 am, john larkin wrote: >>>>>>>>>>>> On Sat, 28 Mar 2026 16:44:40 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>>>>>> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> On 28/03/2026 5:39 am, john larkin wrote: >>>>>>>>>>>>>> On Sun, 22 Mar 2026 03:00:16 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>>>>>>>> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> On 22/03/2026 1:52 am, john larkin wrote: >>>>>>>>>>>>>>>> On Sat, 21 Mar 2026 16:36:43 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>>>>>>>>>> wrote: >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> On 20/03/2026 4:05 am, john larkin wrote: >>>>>>>>>>>>>>>>>> On Tue, 17 Mar 2026 22:30:01 +0000, someone >>>>>>>>>>>>>>>>>> <cffbf4deb9142bce48974efc0e64dede@example.com> wrote: >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> I assume these are up-counters, so the thing overflows at all 1's. Then you only have the one fast carry TPD for the MS18b overflowing to all 1s when a 1 is clocked into its LSB. One whole clock period to clock the 1 out of the DFF and meet the setup times for what I assume is a synchronous LD and its setup for the counters. So that particular timing criticality is a DFF TPD and a LD setup TSU to reliably capture the register data. The LD TPD to CLK TSU for the LS18b counter shouldn't be a problem. This must be very speedy logic for 150MHz. Do you have a simulator that displays how much margin you have on this timing, or is it just a bunch waveforms? >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> Yes, loadable up-counter with carry chain. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> This would be in an FPGA, so the diagram is just a concept. The >>>>>>>>>>>>>>>>>> reality will be VHDL code. And the FPGA boys use the Wishbone >>>>>>>>>>>>>>>>>> architecture and want the counter to be 32 bits, which is OK with me. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> We are already doing a DDS at 250 MHz on this chip, an Efinix T20, so >>>>>>>>>>>>>>>>>> I expect we could do a divider in that ballpark. The T20 is in the >>>>>>>>>>>>>>>>>> *slow* Efinix family. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> I think the T20 has 18-bit fast carry chains. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> After the boys code this, the tools can verify timing. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> FPGAs are great, but there's a cultural gap between people who draw >>>>>>>>>>>>>>>>>> and people who type. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Can't say I've noticed that, but since I can do both, and most of the >>>>>>>>>>>>>>>>> engineers I've hung out with could too, John Larkin may be projecting here. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> Gosh Bill, you are wonderful. You are great at everything. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> I'm certainly not great at writing VHDL. There's a VHDL text-book on my >>>>>>>>>>>>>>> bookshelf - bought for a project which didn't come off - but the stuff I >>>>>>>>>>>>>>> did type was in a much less powerful language, but powerful enough to >>>>>>>>>>>>>>> get the chip to do what I wanted it to. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> What are you designing now? >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Absolutely nothing. I do fish for work from time to time, but at 83 I'm >>>>>>>>>>>>>>> not an attractive employee. >>>>>>>>>>>>>> >>>>>>>>>>>>>> Join one of those maker space things, meet some people, offer to help >>>>>>>>>>>>>> for free, see what happens. >>>>>>>>>>>>> >>>>>>>>>>>>> I'm active on the committee of NSW branch of the IEEE but I don't know >>>>>>>>>>>>> of any maker space things in Sydney. >>>>>>>>>>>> >>>>>>>>>>>> Hey, you could google >>>>>>>>>>>> >>>>>>>>>>>> maker spaces sydney australia >>>>>>>>>>> >>>>>>>>>>> https://makerspaces.com.au/nsw/sydney >>>>>>>>>>> >>>>>>>>>>> So they exist. Leather work and needle work (sewing) are supported. I am >>>>>>>>>>> a tolerably competent carpenter so I might fit in. As a route into >>>>>>>>>>> advanced electronic design it doesn't look promising. >>>>>>>>>> >>>>>>>>>> We have some of that handicraft stuff here, but we have a lot of >>>>>>>>>> people who want to build things that use electronics, and those people >>>>>>>>>> aren't usually very good circuit designers. [1] >>>>>>>>>> >>>>>>>>>> Some of them are actual startups with an idea and some funding. They >>>>>>>>>> go to meetups to pitch their ideas and maybe meet people who could >>>>>>>>>> help. >>>>>>>>>> >>>>>>>>>> Studio 45 near here has an occasional meetup with 500 people, free >>>>>>>>>> food and beer. We might sponsor one. >>>>>>>>>> >>>>>>>>>> We had a cool one at a Rivian facility. I met a photonics consultant >>>>>>>>>> and recommended Phil's book. And listened to yet another pitch for AI >>>>>>>>>> circuit/pcb design. >>>>>>>>>> >>>>>>>>>> There's one coming up in a pier on the SF Bay, an ocean >>>>>>>>>> instrumentetion outfit. That should be fun. >>>>>>>>>> >>>>>>>>>> I do one or two meetups per month and meet lots of Young Things. >>>>>>>>>> >>>>>>>>>> The point is that you could show up, and meet people who need >>>>>>>>>> electronics, and see what happens. >>>>>>>>> >>>>>>>>> If I showed up at the right meetings, I might meet people who needed >>>>>>>>> electronics. The odds don't look great. >>>>>>>>> >>>>>>>>>> Or don't. >>>>>>>>> >>>>>>>>> That would seem to be the rational choice. >>>>>>>> >>>>>>>> Exactly. Do nothing. Just post insults on forums all day. >>>>>>> >>>>>>> I post information. When it doesn't inform people that you are a >>>>>>> brilliant circuit designer, you feel insulted, though you should be used >>>>>>> to that by now. >>>>>>> >>>>>>>>>> [1] It's impressive how few people are good at electronic design. >>>>>>>>> >>>>>>>>> Even more impressive that you seem to think you can make that statement. >>>>>>>>> If you don't think that a classical emitter-coupled monostable can work, >>>>>>>>> your status as a judge of electronic design quality can't be all that high. >>>>>>>> >>>>>>>> That circuit can certainly work; it's classic=ancient. But not often >>>>>>>> useful in this modern world. I didn't like your version because the >>>>>>>> input trigger had to be delicately tuned to fire it, and it really >>>>>>>> amplified the input pulse more than it one-shotted. It was Spice tuned >>>>>>>> until it appeared to work. >>>>>>> >>>>>>> Many applications have well-defined trigger pulses. I certainly didn't >>>>>>> spend any time "deliberately tuning" the circuit. >>>>>>> >>>>>>> The trigger pulse has to be big enough and fast enough to turn off the >>>>>>> normally-on transistor and push enough current into the timing capacitor >>>>>>> to get the one-shot action, and the amplification is incidental to that. >>>>>>> >>>>>>> You didn't recognise the circuit, couldn't see how it worked, and have >>>>>>> been trying to deny this obvious point ever since. >>>>>> >>>>>> That circuit is in the 1964 GE Transistor Manual (7th edition, $2). >>>>>> Transistors used to be expensive so their use was minimized. Nowadays >>>>>> they cost about nothing. >>>>> >>>>> Using a broad-band transistor in a classic circuit can give you a much >>>>> shorter pulse. Broad-band transistors aren't all that cheap, and there >>>>> aren't as many of them around as there used to be, but it can be a >>>>> useful option. >>>>> >>>>>>> This isn't the kind >>>>>>> of comment you like reading, and will claim that you are being insulted. >>>>>>> Tough. This isn't some kind of mutual approbation society >>>>>>> >>>>>>>> There are far better, easier, cheaper, more deliberate ways to make a >>>>>>>> fast one-shot these days. >>>>>>> >>>>>>> Which is to say, to make a one-shot whose action you can understand >>>>>> >>>>>> I usually design circuits that I understand, but what matters is that >>>>>> they work. >>>>>> >>>>>> With Spice or experiment, one can profitably design a circuit that you >>>>>> don't understand. I have a cool new sensor simulator circuit that I >>>>>> don't understand. >>>>> >>>>> You really don't want to. They have a nasty habit of doing something >>>>> unexpected at inconvenient moments. >>>> >>>> That's not a nasty habit, it's a talent that I practice and teach. >>> >>> That's a really nasty habit. Encouraging people to build circuits that >>> can go wrong when they run into a situation that the designer hadn't >>> expected is - to put it kindly - unwise. >> >> Invention is precisely running into - running toward - the unexpected. > >That's a bizarre way of looking at it. It's doing something in a way >that hasn't been done before, but it is goal directed, and you wouldn't >start the process if you didn't have a pretty clear idea of what you >wanted to do, if not exactly how you were going to do it. I strongly disagree; that is backwards. Sometimes we imagine products or circuits that nobody ever wanted or expected. It just happens sometimes at 2AM. I have a folder full of ideas, most speculative and unexpected and probably dumb. We hire smart kids, college students, to explore them and write up a report on the possible uses, competitors specs and pricing, any interesting offshoots that occurr to them. They get a fixed fee when they turn in the report. > >> Sometimes that's accidental, but can be deliberately provoked. >> Inventing needs the right skills and personality but improves with >> practice in the right environment. Books have been written about that. > >None of them useful enough to have been touted at places that encouraged >inventions and applying for patents. EMI Central Research was just such >a place, and I worked there for three years without ever running into >such a book. The histories of Bell Labs > >https://en.wikipedia.org/wiki/The_Idea_Factory > I have that one; good book. Someone said that all the great inventions at Bell in those days were done by people who ate lunch with Harry Nyquist. >didn't mention any such book either. People will write books with the >flimsiest of justifications if they think the product will sell. >Teaching people how to make genuine inventions would be a very good >thing if you could do it, and a lot of confidence tricksters claim that >they can. The evidence supporting such claims doesn't seem to exist. The real evidence is purchase orders. > >> Some people invent things. Some intelligent and (over)educated people >> actively resent invention, because they can't do it. > >I can't say that I've met any of them. My father and two of my friends >have each got their names onto about 25 patents and none of them ever >talked about people resenting that work. > >>>> Given an enormous space of undiscovered ideas, one profits from a >>>> method of exploring them in parallel with minimal filtering. > >At EMI Central Research we were encourage to submit patent queries. One >of my colleagues put in a record number of patent queries - about fifty >in one year - and was seen as having rather poor judgement. None of them >turned into a patent. He would have benefited from better filtering. The real evidence is purchase orders. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
Back to comp.arch.fpga | Previous | Next — Previous in thread | Next in thread | Find similar
fast divider? john larkin <jl@glen--canyon.com> - 2026-03-15 11:47 -0700
Re: fast divider? someone <cffbf4deb9142bce48974efc0e64dede@example.com> - 2026-03-17 22:30 +0000
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-19 10:05 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-21 16:36 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-21 07:52 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-22 03:00 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-27 11:39 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-28 16:44 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-28 14:38 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-29 15:52 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-29 08:18 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-30 16:42 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-30 08:00 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-31 16:35 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-31 02:40 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-31 22:30 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-31 08:14 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-01 15:54 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-01 01:06 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-02 02:13 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-01 09:12 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-02 14:41 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-02 07:53 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-03 02:21 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-02 08:57 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-03 04:05 +1100
Re: fast divider? someone <cffbf4deb9142bce48974efc0e64dede@example.com> - 2026-03-26 23:30 +0000
Re: fast divider? Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-03-21 09:38 -0700
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-21 10:29 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-23 23:49 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-23 08:20 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-24 23:04 +1100
Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-24 05:56 -0700
Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-25 02:47 +1100
csiph-web