CF cards can receive power on pin 20.

kingcake wrote on 2024-03-19, 08:39:

CF cards can receive power on pin 20.

Pin 20 is marked as “missin pin” that means factory can connect it to +5v or not? and why? to feed what?

i'd like to know on what chipsets this power on pin 20 is prevalent on.

AlessandroB wrote on 2024-03-19, 08:16:

To my incredible surprise, by mounting the adapter you see in the photo without connecting it to the power supply, it works perfectly! I didn't think it would take power from the normal 40-pin IDE cable, but is this something expected? Doesn't it overload the IDE controller circuitry?

Beware that if you're not getting power explicitly on pin 20 it means the card is working essentially through unintended paths and/or leakage and that might very well lead to data corruption and even loss of the cf card.
I had this happen to me when I plugged an adapter to a controller card and forgot to power it explicitly and it borked the cf card.

If you want things to be neater either add power to pin 20 (if it's physically on the motherboard connector) or you can bring 5V from any other header on the board like for example USB or IRdA, you just need a single female-female dupont cable (ground is already well connected)

stanwebber wrote on 2024-03-19, 12:34:

i'd like to know on what chipsets this power on pin 20 is prevalent on.

Most modern XTide cards have this as an option.

Yrouel wrote on 2024-03-19, 12:46:

Beware that if you're not getting power explicitly on pin 20 it means the card is working essentially through unintended paths a […]
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AlessandroB wrote on 2024-03-19, 08:16:

To my incredible surprise, by mounting the adapter you see in the photo without connecting it to the power supply, it works perfectly! I didn't think it would take power from the normal 40-pin IDE cable, but is this something expected? Doesn't it overload the IDE controller circuitry?

Beware that if you're not getting power explicitly on pin 20 it means the card is working essentially through unintended paths and/or leakage and that might very well lead to data corruption and even loss of the cf card.
I had this happen to me when I plugged an adapter to a controller card and forgot to power it explicitly and it borked the cf card.

If you want things to be neater either add power to pin 20 (if it's physically on the motherboard connector) or you can bring 5V from any other header on the board like for example USB or IRdA, you just need a single female-female dupont cable (ground is already well connected)

if the card wont take power from pin20... wich one can provide? all the other are data cable...

anyway, if i measure 5v on my pin20 i can be sure that my adapter take power from it in a correct way?

AlessandroB wrote on 2024-03-19, 19:47:

Yrouel wrote on 2024-03-19, 12:46:

Beware that if you're not getting power explicitly on pin 20 it means the card is working essentially through unintended paths a […]
Show full quote

AlessandroB wrote on 2024-03-19, 08:16:

To my incredible surprise, by mounting the adapter you see in the photo without connecting it to the power supply, it works perfectly! I didn't think it would take power from the normal 40-pin IDE cable, but is this something expected? Doesn't it overload the IDE controller circuitry?

Beware that if you're not getting power explicitly on pin 20 it means the card is working essentially through unintended paths and/or leakage and that might very well lead to data corruption and even loss of the cf card.
I had this happen to me when I plugged an adapter to a controller card and forgot to power it explicitly and it borked the cf card.

If you want things to be neater either add power to pin 20 (if it's physically on the motherboard connector) or you can bring 5V from any other header on the board like for example USB or IRdA, you just need a single female-female dupont cable (ground is already well connected)

if the card wont take power from pin20... wich one can provide? all the other are data cable...

anyway, if i measure 5v on my pin20 i can be sure that my adapter take power from it in a correct way?

If you see 5v on pin 20, you are probably OK. What IDE controller are you using?

douglar wrote on 2024-03-19, 19:56:

AlessandroB wrote on 2024-03-19, 19:47:

Yrouel wrote on 2024-03-19, 12:46:

Beware that if you're not getting power explicitly on pin 20 it means the card is working essentially through unintended paths and/or leakage and that might very well lead to data corruption and even loss of the cf card.
I had this happen to me when I plugged an adapter to a controller card and forgot to power it explicitly and it borked the cf card.

If you want things to be neater either add power to pin 20 (if it's physically on the motherboard connector) or you can bring 5V from any other header on the board like for example USB or IRdA, you just need a single female-female dupont cable (ground is already well connected)

if the card wont take power from pin20... wich one can provide? all the other are data cable...

anyway, if i measure 5v on my pin20 i can be sure that my adapter take power from it in a correct way?

If you see 5v on pin 20, you are probably OK. What IDE controller are you using?

is the one integrated in th IBM pc330 486DX2

for all the people saying pin 20...

pin 20, the keypin, the pin that seems to be missing on OP's photo. That pin is delivering power ?

Truly we live in amazing times.

EDIT: sorry wrong link. I can't find where I wrote that I saw that with a CF card on a Startech IDE to CF adapter. Or maybe I never wrote about it and imagined that I had .
EDIT2: Found Using a vintage multi-track recorder as a mixer, namely the Roland VS-880EX - might apply to other Roland VS- units , but that is not what I remember either. I think I was using the 40-pin input on the CF adapter and am not sure anymore whether I checked pin 2o.

I had a similar surprise with a mysteriously powered CF card . No pin20 either .

Re: What is the current carrying capacity of a wire in 40-pin IDE (ATA) and 44-pin IDE (ATA) cables ?

running on leakage power thru data pins, not a good idea

weedeewee wrote on 2024-03-19, 21:05:

for all the people saying pin 20...

pin 20, the keypin, the pin that seems to be missing on OP's photo. That pin is delivering power ?

Truly we live in amazing times.

I didn’t even think to look at the CF adaptor. Good eye!

weedeewee wrote on 2024-03-19, 21:05:

for all the people saying pin 20...

pin 20, the keypin, the pin that seems to be missing on OP's photo. That pin is delivering power ?

Truly we live in amazing times.

Right I should have clarified. I was making a statement of fact. Didn't mean to imply that's what was happening in OP's case.

beware the passive adapter ! (such HXSP-2108P) there are no regulator or diode on it, my thouught if pin 20 exists then better to not connect the molex or we risk reversing current if psu are not too accurate (eg pin 20 IDE supply +4.9V and red molex +5.2V), it has bigger risk than half powered CF, is my thought make sense?

Whether the CF card works without power connected to the adapter or not, is not a property of the adapter. It is a property of the CF card. Certain cards don't require the power cable to be connected, and some do.

I have CF cards of both kinds.. A 256MB that works without connecting power to the adapter, and a 4Gb card that doesn't work unless you connect the power cable. The adapter has nothing to do with it. You can try several cards to know which ones require power vs ones that work without the cable.

RTID wrote on 2026-01-05, 14:47:

beware the passive adapter ! (such HXSP-2108P) there are no regulator or diode on it, my thouught if pin 20 exists then better to not connect the molex or we risk reversing current if psu are not too accurate (eg pin 20 IDE supply +4.9V and red molex +5.2V), it has bigger risk than half powered CF, is my thought make sense?

i not know....

wbahnassi wrote on 2026-01-05, 19:02:

Whether the CF card works without power connected to the adapter or not, is not a property of the adapter. It is a property of the CF card. Certain cards don't require the power cable to be connected, and some do.

I have CF cards of both kinds.. A 256MB that works without connecting power to the adapter, and a 4Gb card that doesn't work unless you connect the power cable. The adapter has nothing to do with it. You can try several cards to know which ones require power vs ones that work without the cable.

Very interesting.. i will try tnks