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A Question about DOMs

Stone

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Nov 3, 2009
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12,814
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Can somebody explain why the DOM runs fine even when not connected to the PSU? It not only runs fine but the machine also boots from it normally. Does it actually use that 5V for anything?
 

3pcedev

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Jun 8, 2014
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Australia
40 pin IDE or 44 pin?

If 44 pin then it's got power on the IDE cable. If 40 pin it might be using a signal wire that is normally high to power itself (i.e. I think the reset pin is inverted).
 

glitch

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Feb 1, 2010
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It can draw power from pin 20 on the IDE connector. Not all IDE connectors supply +5 on pin 20 (on many connectors it's a key pin and thus omitted), so sometimes you need the Molex pigtail.
 

Osgeld

Experienced Member
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Feb 20, 2016
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Tennessee
damn beat me to it, pin 20 is the keypin, which means it may or may not exist, it may or may not be blocked off on the cable, originally it was connected to the 5v bus but proved somewhat pointless when connected though the molex power connection

this used to drive me bonkers back in the day so i would take out a knife and remove the plastic plug from the cable to get it to fit in older machines, and of course it was connected internally, just a peg of plastic jammed in the cable for pentium and some later 486 machines for DURH HUHAHUA pleebs to have double poka-yoke when inserting their IDE cables with a hammer
 
Last edited:

glitch

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DOMs don't connect via a cable, at least not natively. :)

You can get male 40-pin IDC connectors for ribbon cables, I use them all the time for DOM refits where the DOM has to share an IDE channel with something else (CD-ROM, Zip drive, whatever).
 

Stone

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You can get male 40-pin IDC connectors for ribbon cables, I use them all the time for DOM refits where the DOM has to share an IDE channel with something else (CD-ROM, Zip drive, whatever).
Ya', that's what I meant by 'not natively'. :)

For reference, which ones have you been using?
 
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