3 ms·

You clearly aren't a retrocomputing hobbyist, so you aren't in the know. Trust me, autorouting is essential for some use cases, and it works great for those app

You clearly aren't a retrocomputing hobbyist, so you aren't in the know. Trust me, autorouting is essential for some use cases, and it works great for those applications.

sweetjuly 3y ago
What's so special about retrocomputing that makes it more tractable for autorouting? Autorouting isn't a thing in industry for PCB design because managing EMI for modern ICs is so challenging. Is retrocomputing able to get away with it due to slow rise times on very old chips?
- phendrenad2 3y ago
  Exactly, EMC is only really an issue above 50MHz, much higher than most retrocomputers were capable of.
  - bogantech 3y ago
    The issue is not the frequency of your signals but the edge rate.
    - phendrenad2 3y ago
      That's... not entirely true actually.
LIV2 3y ago
I am, and I have made a few popular designs. I would consider it absolutely unnecessary, and invariably results in something that is unreliable at best. Do you have examples that show how it is essential?
- phendrenad2 3y ago
  You'd route 100+ signals by hand on a two-layer board? You either have too much money or too much time.
  - deleted 3y ago
    [deleted]
  - LIV2 3y ago
    Yes I have done so several times. 2 layer and 4 layer. I can't see how it would cost me money to do so, on the other hand if I was to blindly autoroute my designs i'd spend more time troubleshooting and way more money doing several revisions before I got something stable.
    - phendrenad2 3y ago
      What problems would you expect to find when blindly autorouting? I have to admit, I've only used two auto-routers in my life. Both were in Altium CircuitMaker. The first one was flawless, the second one was unusable. So maybe yours is more on the unusable end?
      - neltnerb 3y ago
        I think an autorouter does come in handy, but not if you use it blindly. How well it does is as you would expect of any other tool that operates without complete information. It can't trivially tell which areas of your board you have intended for analog signals, or where high speed things are. When you autoroute a 2 layer board (in particular) if you don't drop vias next to ground pins it goes nuts trying to connect ground pins with a ground pour constantly changing. It tries to keep traces as close as possible to edges where a human would really just give it "breathing room". If you want to make a prototype that can be reworked, you need to be super careful (you always do, but it's easier to miss a lack of accessibility if it's automatic). It orients traces in ways that are in accordance with a score metric rather than geometric elegance, legibility, or crosstalk because it doesn't know what signals are where. None of these are unsolvable, but they are the kinds of problems I expect when I use it. That said, if I have 1000 traces to route I will do 970 of them manually and be grateful for the autorouter doing the last 30 that would take me a half day to figure out a clean path for. The problem comes when people think an autorouter is a computer program written by people who know about their PCB and that the results will approximate an expert doing an okay job. Then they realize that's not the case and decide the autorouter cannot do a decent job ever. Much later they realize that if they actually learn how the autorouter works they can use it as a tool to do... what the autorouter is programmed to do. But it can't read the designer's mind.

You clearly aren't a retrocomputing hobbyist, so you aren't in the know. Trust me, autorouting is essential for some use cases, and it works great for those applications.

sweetjuly 3y ago

What's so special about retrocomputing that makes it more tractable for autorouting? Autorouting isn't a thing in industry for PCB design because managing EMI for modern ICs is so challenging. Is retrocomputing able to get away with it due to slow rise times on very old chips?

phendrenad2 3y ago
Exactly, EMC is only really an issue above 50MHz, much higher than most retrocomputers were capable of.
- bogantech 3y ago
  The issue is not the frequency of your signals but the edge rate.
  - phendrenad2 3y ago
    That's... not entirely true actually.

LIV2 3y ago

I am, and I have made a few popular designs. I would consider it absolutely unnecessary, and invariably results in something that is unreliable at best. Do you have examples that show how it is essential?

phendrenad2 3y ago
You'd route 100+ signals by hand on a two-layer board? You either have too much money or too much time.
- deleted 3y ago
  [deleted]
- LIV2 3y ago
  Yes I have done so several times. 2 layer and 4 layer. I can't see how it would cost me money to do so, on the other hand if I was to blindly autoroute my designs i'd spend more time troubleshooting and way more money doing several revisions before I got something stable.
  - phendrenad2 3y ago
    What problems would you expect to find when blindly autorouting? I have to admit, I've only used two auto-routers in my life. Both were in Altium CircuitMaker. The first one was flawless, the second one was unusable. So maybe yours is more on the unusable end?
    - neltnerb 3y ago
      I think an autorouter does come in handy, but not if you use it blindly. How well it does is as you would expect of any other tool that operates without complete information. It can't trivially tell which areas of your board you have intended for analog signals, or where high speed things are. When you autoroute a 2 layer board (in particular) if you don't drop vias next to ground pins it goes nuts trying to connect ground pins with a ground pour constantly changing. It tries to keep traces as close as possible to edges where a human would really just give it "breathing room". If you want to make a prototype that can be reworked, you need to be super careful (you always do, but it's easier to miss a lack of accessibility if it's automatic). It orients traces in ways that are in accordance with a score metric rather than geometric elegance, legibility, or crosstalk because it doesn't know what signals are where. None of these are unsolvable, but they are the kinds of problems I expect when I use it. That said, if I have 1000 traces to route I will do 970 of them manually and be grateful for the autorouter doing the last 30 that would take me a half day to figure out a clean path for. The problem comes when people think an autorouter is a computer program written by people who know about their PCB and that the results will approximate an expert doing an okay job. Then they realize that's not the case and decide the autorouter cannot do a decent job ever. Much later they realize that if they actually learn how the autorouter works they can use it as a tool to do... what the autorouter is programmed to do. But it can't read the designer's mind.