but apparently can be used for power delivery (assuming connected devices support it)

Yes, IDE DOM devices usually can work with that pin. I suppose you can deduce expected power delivery from DOM datasheets.

The Serpent Rider wrote on 2020-10-08, 16:28:

but apparently can be used for power delivery (assuming connected devices support it)

Yes, IDE DOM devices usually can work with that pin. I suppose you can deduce expected power delivery from DOM datasheets.

Thanks. I had looked at one (https://www.digchip.com/datasheets/parts/data … 44MV032-pdf.php) and its power usage is extremely low (< 60 mA), so it does not help establish an upper limit . Additionally, it does not even use pin 20 or any official power pin . I would guess it powers itself directly from data pins since current demand is so low (please correct me if that makes no sense) .

I have looked at specs on drives old 2.5" IDE drives that show current as high as 1A at 5V . The highest current draw I have seen on older, officially supported drives on the VS-880EX is 3.5A 0.7A (3.5W)(http://www.ps139.com/vs880ex/pages/VSCompat.pdf) .

My plan is to run a Samsung 860 EVO (extreme overkill, but it should last essentially forever) through a JMicron JM20330 SATA to IDE bridge . The Samsung is rate at 4W max , 2.2W typical . The power requirements of the JMicron are extremely low. Since it looks like I will be waiting longer than expected for my disk caddy/connection adapter, I am going to build my own (pretty much mostly done) and source power from the 5V "motor" pin (though I suspect both it and the "logic" pin are directly connected to the same supply) and hope I do not fry anything . I have tested this using external power only, so far .

EDIT: Corrected typo

I've found PDF for my InnoDisk EDC4000 DOM and pin 20 is described as following: "In the 40-pin version, this pin is defined as VCC to reduce the need for an external power connector. In
the 44-pin version, this pin is defined as KEY, according to the ATA standard".

InnoDisk EDC4000 has 125mA max power consumption.

So probably 0.5-1A max?

The Serpent Rider wrote on 2020-10-08, 17:25:

I've found PDF for my InnoDisk EDC4000 DOM and pin 20 is described as following: "In the 40-pin version, this pin is defined as […]
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I've found PDF for my InnoDisk EDC4000 DOM and pin 20 is described as following: "In the 40-pin version, this pin is defined as VCC to reduce the need for an external power connector. In
the 44-pin version, this pin is defined as KEY, according to the ATA standard".

InnoDisk EDC4000 has 125mA max power consumption.

So probably 0.5-1A max?

I guess I will have to go with that guess and assume 0.8A will be OK .

Even the official ATA-2 spec, which was current when the VS-880EX was released ( http://www.t13.org/Documents/UploadedDocument … 48r4c-ATA-2.pdf ) does not go any further than pin assignments on the 44-pin connector . I can understand that power requirements of 40-pin devices using a Molex power connector would not need to be defined explicitly in the spec, but I would have thought that at least the 44-pin variant, being constrained by wires on a ribbon cable, would have been .

Assuming 28 gauge wire, (some cables are 26 gauge but I would go conservative and use the 28 gauge for reference), the rating is 0.7 amps. Of coarse this assumes that adequate cooling is available. I.E. the wire is not in a bundle. Since flat ribbon cables are not technically a "bundle", (lots of air around at least 50% of the diameter of the individual wire), you should be OK with 0.7 amps or less. However, I've seen ribbon cables that were essentially turned into a bundle by tightly rolling to make it a round cable, so don't do that and you should be fine. You might want to consider a fuse on the line if it's not currently fused just so that you don't have a melt down or worse.

ibmapc wrote on 2020-10-08, 18:54:

Assuming 28 gauge wire, (some cables are 26 gauge but I would go conservative and use the 28 gauge for reference), the rating is […]
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Assuming 28 gauge wire, (some cables are 26 gauge but I would go conservative and use the 28 gauge for reference), the rating is .7 amps. Of coarse this assumes that adequate cooling is available. I.E. the wire is not in a bundle. Since flat ribbon cables are not technically a "bundle", (lots of air around at least 50% of the diameter of the individual wire), you should be OK with .7 amps or less. However, I've seen ribbon cables that were essentially turned into a bundle by tightly rolling to make it a round cable, so don't do that and you should be fine. You might want to consider a fuse on the line if it's not currently fused just so that you don't have a melt down or worse.

Thank you for that information . Unfortunately that puts a crimp (pun intended) on my plans . The 50-pin "SCSI" ribbon cable that I am using for testing is 28AWG, as are all my other 50-pin cables . The very short 50-pin cable that came with the unit subjectively looks like a slightly bigger gauge (hard to tell, TBH). I guess I could use a 28AWG 40-pin cable for data and a separate bigger gauge cable pair for power delivery, though it makes it a lot less convenient .

Maybe I am just worrying too much and trying to over-engineer it as the VS-880EX will probably never be able to drive the 860 EVO hard enough to reach its 0.8A max (burst mode) .

Anyway a fuse is probably a good idea anyway . What fuse rating/type would you suggest ?

I'd go with a 0.7 amp (700 mA) slow-blow. I think you'll be fine. Run it for a while at full load (don't think you can maintain burst mode for long, just do a big write to it) and feel the cable. If it stays cool, you're probably OK. Especially with the fuse in line. I run power to external 5-1/4 floppy drive though a ribbon cable and have never seen the cable get warm at all.

ibmapc wrote on 2020-10-08, 20:00:

I'd go with a 0.7 amp (700 mA) slow-blow. I think you'll be fine. Run it for a while at full load (don't think you can maintain burst mode for long, just do a big write to it) and feel the cable. If it stays cool, you're probably OK. Especially with the fuse in line. I run power to external 5-1/4 floppy drive though a ribbon cable and have never seen the cable get warm at all.

Thanks . I will give my setup some more thought .

1A is about max for a pin in the connector, and seems cable itself is less capable. There will be some level of heating, depending on (contact) resistance but in general it isn't gonna be a problem unless you try to do something overkill 🤣.

44 pin ATA connector used 4 pins for power, are two ground return, two for 5V supply, rest is signal ground. Hard drives of these 2.5" usually 1A surge during start up.

Cheers,