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  • DIY Laplink cable results

    From kirkspragg@21:2/150 to All on Fri Aug 15 21:15:35 2025
    Hi everyone, hope your weekend has started off well & that your weekend is good to you.

    So i got round to putting together the 5m long laplink parallel port data transfer cable. I ended up using the 'Parallel Transfer Mode 0' cable schematics from docs.kernel.org/networking/plip.html and used 3 parallel runs of some cheap 4 core shielded speaker wire from our local hobby electronics store:
    https://www.jaycar.co.nz/4-core-round-screened-audio-cable/p/WB1510

    Soldering 12 wires from 3 different multi-core cables into the DB25 plugs was a bit of a hassle & with three runs of cable between the plugs. The cables barely fit in the plug housing -but they did fit with some light encouragement. I just tested it out & it works!

    Getting around 20KB/s between dosbox running on my main PC and my 386DX40 & I think that a reasonably speed to get form the old standard parallel port in my 386, I'm stoked!

    Supposed I should put together a serial null modem cable and try that out as well. I expect the speed will be quite a bit less.

    ... A friend asks only for your time, not your money.

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  • From poindexter FORTRAN@21:4/122 to kirkspragg on Sun Aug 17 07:58:03 2025
    kirkspragg wrote to All <=-

    Soldering 12 wires from 3 different multi-core cables into the DB25
    plugs was a bit of a hassle & with three runs of cable between the
    plugs. The cables barely fit in the plug housing -but they did fit
    with some light encouragement. I just tested it out & it works!

    My first IT job had me soldering 100 DB25s onto some kind of shielded cable, forget what type. It was a pain, but at least it was one cable per
    connector!



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  • From kirkspragg@21:2/150 to poindexter FORTRAN on Mon Aug 18 12:53:00 2025
    My first IT job had me soldering 100 DB25s onto some kind of shielded cable, forget what type. It was a pain, but at least it was one cable per connector!

    That would have made it a bit easier, did you have a decent soldering setup to help you hold the connector & cable in place while soldering together?

    I kinda made do with my basic temp controlled iron and a single bench clamp to hold the plug.... next time i'll have 2nd clamp of some sort to hold the cables. Its far too fiddly and error prone otherwise - I only slightly melted the plastic of one of the plugs when I slipped with the iron. Man am I out of practice wielding a soldering iron!

    ... Help! I've fallen and I can't Hey! Nice carpet!

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  • From poindexter FORTRAN@21:4/122 to kirkspragg on Mon Aug 18 13:14:47 2025
    Re: Re: DIY Laplink cable results
    By: kirkspragg to poindexter FORTRAN on Mon Aug 18 2025 12:53 pm

    That would have made it a bit easier, did you have a decent soldering setup to help you hold the connector & cable in place while soldering together?

    A pair of vise-grips. :)
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  • From Bob Worm to kirkspragg on Tue Aug 19 19:48:31 2025
    Re: DIY Laplink cable results
    By: kirkspragg to All on Fri Aug 15 2025 21:15:35

    Hi, kirkspragg.

    So i got round to putting together the 5m long laplink parallel port data transfer cable.

    I just tested it out & it works!

    I just wanted to let you know that you're my personal hero :)

    BobW
  • From Retroswim@21:2/121 to kirkspragg on Wed Aug 20 11:10:12 2025
    Getting around 20KB/s between dosbox running on my main PC and my 386DX40 & I think that a reasonably speed to get form the old standard parallel port in my 386, I'm stoked!

    Hell yeah!

    What transfer software are you using? Back in the day, we used a package called "FastLynx", it could get around a megabit of throughport between 486es, using a standard LapLink parallel cable. I have to assume using some
    form of compression?

    Cheers,
    RetroSwim

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  • From Bob Worm to Retroswim on Wed Aug 20 21:04:57 2025
    Re: DIY Laplink cable results
    By: Retroswim to kirkspragg on Wed Aug 20 2025 11:10:12

    What transfer software are you using? Back in the day, we used a package called "FastLynx", it could get around a megabit of throughport between 486es, using a standard LapLink parallel cable. I have to assume using some form of compression?

    Every time anyone mentions Laplink I go off into a mental rabbit hole and think that I might have to whip out the ol' logic analyser and sniff a Laplink connection to see how it works. My cheapo logic analyser only has 8 pins, though, so I guess it'll have to be serial. At a guess parallel would use the same protocol over the top.

    Maybe it would be easier to MitM it using a system with two serial ports. If it relies on hardware handshaking, though, I might have to bypass those through at first.

    Hmmmm...

    BobW
  • From kirkspragg@21:2/150 to Bob Worm on Fri Aug 22 22:11:20 2025
    So i got round to putting together the 5m long laplink parallel port da transfer cable.

    I just tested it out & it works!

    I just wanted to let you know that you're my personal hero :)

    BobW
    Oh that so cool to hear!

    Seriously it wasn't exactly hard wire/solder everything up as a bit tedious and occasionally frustrating. You could do it yourself assuming you've got a decent soldering iron & a couple of bench vices to hold stuff in place.

    I've just finished making a 5m long null modem cable as well, did it "properly" with the hardware handshaking lines crossed over as per http://www.nullmodem.com/NullModem.htm. I was hoping that having hardware handshaking wired would enable me to use a baud rate > 9600 with my old 386.

    TLDR; Nope. The highest best rate that doesn't cause failures or crash the com port is 9600 baud. Turns out the UART in the multi-io card is a 16450 and so just can't do any better.

    ... All stressed out, and no one to choke.

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  • From kirkspragg@21:2/150 to Retroswim on Fri Aug 22 22:18:43 2025
    I think that a reasonably speed to get form the old standard parallel in my 386, I'm stoked!

    Hell yeah!

    What transfer software are you using? Back in the day, we used a package called "FastLynx", it could get around a megabit of throughport between 486es, using a standard LapLink parallel cable. I have to assume using some form of compression?

    Yea I'm using FastLynx. My past experience with laplink hasn't been so great as it tends to just die on long running transfers. Fastlynx on the other hand seems quite stable.

    Fastlynx can do compression (which I disabled for my benchmarking) so that would help. What speed 486es were they? anyting but a lowely 486sx25 should perform much better than my 386dx40, I wonder if that would lead to better parallel port data transfer rate?

    Also it is possible your 486es had 'proper' bi-diretional EPP parallel ports which would increase the speed quite a lot - but I think you need a different cable that the one I made for that but I'm not completely sure.

    ... Hear no evil, speak no evil, C:\NOEVIL

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