VOGONS


First post, by Overlord_Manny

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This question may sound crazy but let me explain. I've been playing some old DND titles on my 486, Menzoberranzan & Ravenloft: Strahd's Possession. Anyone familiar with those games, and many other DOS titles actually, will remember that movement was hard coded to use the number pad. The mouse is also used for menu navigation in those games. I'm right handed and my aging back sure doesn't like the fact that both of my hands are being held to the right side of my body for a long periods. I thought getting an add-on PS/2 keypad and putting it to the left of my keyboard might be the answer and I bought one on ebay for pretty cheap. Sadly, I didn't think about the fact that biggest reason for needing an add-on PS/2 keypad back in the day would be using it for a laptop that didn't have one. I thought there would be a passthrough plug for a full keyboard, but I was mistaken. I know they make PS/2 splitters for those later 2000's PC's that had shared mouse and keyboard plugs, but I imagine that they are wired differently than I would need. I'm fine with crafting my own splitter, but would that even work or could it possibly draw too much power from the port. I sure don't want to wreck neither my 486 or my P1-233MMX that are shared on a KVM. Anyone have any experience with something like this?

TLDR: Can a splitter be bought/made that will achieve adding an add-on PS/2 numberpad to the same PS/2 port as the full keyboard and is it safe to do so?

Reply 1 of 3, by Plasma

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I don't think a dumb splitter will work. There are PS/2 numpads designed for left-hand users that have a PS/2 passthrough for the main keyboard. Cherry G80-3700 for example. PC Concepts KB5640 and/or Fellowes 99907 may also have a passthrough since it's marketed as "perfect for left handed desktop users", although I cannot find any photos confirming this.

Reply 2 of 3, by FuST

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This might be a good place to start: http://www.burtonsys.com/PS2_keyboard_and_mou … or_pinouts.html
Especially the second cable pinout is of interest as it seems to suggest that simply connecting the keyboards in parallel should work, though I can't see how when looking at the PS/2 hardware protocol.
The pinout hints toward a second CLK line being used for a Y-splitter for keyboard/mouse (https://pinouts.ru/InputCables/KeyboardPC6_pinout.shtml) but that's not the case for the multi-keyboard splitter.
I would think, with my somewhat limited knowledge of PS/2, sharing the CLK and DATA lines would lead to bus contention when used simultaniously as both keyboards will try to send data.

I don't think this would overload the PS/2 port any more than a keyboard/mouse combo would.

TL;DR: Looks like it should be possible though at the moment I can't see how that would work on a hardware protocol level.

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Reply 3 of 3, by debs3759

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As the keyboard is powered by the computer port, I don't see why it wouldn't work. The main keyboard and the keypad wouldn't generally be outputting signals at the exact same moment, so whatever key you press on each would be recognised. I would expect even key combinations such as CTRL-ALT-DEL using both would work.

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