does anyone know why a PCI-E video card's power connector is only 12v (yellow) and G, while the power connector on......

[computer]

Guys, does anyone know why a PCI-E video card's power connector is only 12v (yellow) and G, while the power connector on AGP 8x video cards (that have them), are 12v, G, AND a 5v (red) line?

Reason I ask is I recently got a new PSU that's modular and it has two labeled dedicated PCI-E modular cables. I was hoping I could use one of these for my AIW 9800 Pro, since I've always heard you should use a separate dedicated power cable for a video card (hence the separate dedicated PCI-E modular cables). But I can't, I apparently can't even adapt it to work with a mod'ed connector since the PCI-E connector is missing the red 5v wire. So I'm wondering that since my card for example uses a floppy power connector, if the 5v line may be "empty", as in it not being needed nor actually connected to anything on the card. If that's the case, then I easily mod the PCI-E cable to work with my card.

If not, then I'm going to have to use one of the huge cables with 4 of the large 4-pin Molex connectors on it just to be able to use a floppy power connector! Even if I adapt one of the 4-pin Molex to floppy connector, I'd still have to use the entire cable assembly for only one device, which defeats the purpose of me getting a modular PSU in the first place.
Thanks.

 

[letdown427]

Could be AGP cards drained 7volts instead of 12. But other than that, I don't know, sorry.

 

[MDE]

What other plugs were around before PCIe? Logic says it should work but I don't know if it'll actually use any power off the 5v line. If you're not going to need your old PSU you could try cutting the 5v wire on the connector to the AIW and see if it still works afterwards (tape the ends of the wire while it's powered on).

 

[computer]

Originally posted by: letdown427
Could be AGP cards drained 7volts instead of 12. But other than that, I don't know, sorry.

Thanks for the bump at least.

 

[computer]

Originally posted by: MDE
What other plugs were around before PCIe? Logic says it should work but I don't know if it'll actually use any power off the 5v line. If you're not going to need your old PSU you could try cutting the 5v wire on the connector to the AIW and see if it still works afterwards (tape the ends of the wire while it's powered on).

Plugs for video cards? None that I know of.

That's a good idea, thanks. I have all sorts of power adapters and I can cut the 5v line on one of the floppy drive power connectors and hook that to it. If the card does NOT work then that says a lot. But it if still does work, the line still could be needed for certain things FAIK that wouldn't show themselves unless under specific conditions. Might be for the fan, does anyone know if the video card GPU fans are 5v or 12v? My guess is they are 12v, but I've never messed with any of them so I don't know for sure.

 

[Continuity28]

Originally posted by: letdown427
Could be AGP cards drained 7volts instead of 12. But other than that, I don't know, sorry.

No, I believe the red 5V was simply not used. That's the good thing about molex, but they wanted a better source of power for more modern cards and opted to make a better cable specially for it.

EDIT: Ignore post

 

[computer]

Originally posted by: Continuity28

Originally posted by: letdown427
Could be AGP cards drained 7volts instead of 12. But other than that, I don't know, sorry.

No, I believe the red 5V was simply not used. That's the good thing about Molex, but they wanted a better source of power for more modern cards and opted to make a better cable specially for it.

Are you saying you think the red 5v isn't used on AGP cards? I looked at the connector fairly good on my card and there are indeed 4 pins (Y-B-B-R) just like the large 4-pin Molex and floppy connector, and they all soldered to the PCB. Now it's possible the red 5v ends right there, no trace after that connector. But if that were the case I'd think there wouldn't even be a pin there to "accept" the red 5v wire. I could look at it closer to see if I can tell if the 5v continues onward after that, but I'd have to remove it and disconnect all sorts of BS. I don't want to risk using a voltmeter on it hot to try and trace it even with sharp leads because I could still short something.

I'll wait for some more input. :clock:

 

[Continuity28]

Originally posted by: computer

Originally posted by: Continuity28

Originally posted by: letdown427
Could be AGP cards drained 7volts instead of 12. But other than that, I don't know, sorry.

No, I believe the red 5V was simply not used. That's the good thing about Molex, but they wanted a better source of power for more modern cards and opted to make a better cable specially for it.

Are you saying you think the red 5v isn't used on AGP cards? I looked at the connector fairly good on my card and there are indeed 4 pins (Y-B-B-R) just like the large 4-pin Molex and floppy connector, and they all soldered to the PCB. Now it's possible the red 5v ends right there, no trace after that connector. But if that were the case I'd think there wouldn't even be a pin there to "accept" the red 5v wire. I could look at it closer to see if I can tell if the 5v continues onward after that, but I'd have to remove it and disconnect all sorts of BS. I don't want to risk using a voltmeter on it hot to try and trace it even with sharp leads because I could still short something.

I'll wait for some more input. :clock:

You know what, I take back what I said.

I have reason to believe that AGP video cards used power on all 3 rails, 3.3V, 5V, and 12V. All three are able to come through the AGP port, but when the card needs more power, it uses the molex connector for additional 5V and 12V power. 3.3V is only carried in the slot.

 

[computer]

I have reason to believe that AGP video cards used power on all 3 rails, 3.3V, 5V, and 12V. All three are able to come through the AGP port, but when the card needs more power, it uses the molex connector for additional 5V and 12V power. 3.3V is only carried in the slot.

That's what I had originally thought. Now to find out why--Why it needs 5v when the PCI-E does not.

 

[Continuity28]

Originally posted by: computer

I have reason to believe that AGP video cards used power on all 3 rails, 3.3V, 5V, and 12V. All three are able to come through the AGP port, but when the card needs more power, it uses the molex connector for additional 5V and 12V power. 3.3V is only carried in the slot.

That's what I had originally thought. Now to find out why--Why it needs 5v when the PCI-E does not.

Probably not the answer you're really looking for... but I think they just changed the video card internally so that it doesn't use 5V power at all. I know, for example, PCI-Express slots only carry 12V and 3.3V power, and the 6 pin connector only carries 12V power, which means PCI-E cards use NO 5V power. I'm not sure if your AGP card does use 5V power, but the AGP slot and external connectors would carry it.

 

[computer]

If you're positive then it's the answer I'm looking for.

Looks like the only thing to do so far to be sure is what "MDE" suggested about cutting the 5v line and seeing if the card still works.

 

[DeathReborn]

Originally posted by: computer

I have reason to believe that AGP video cards used power on all 3 rails, 3.3V, 5V, and 12V. All three are able to come through the AGP port, but when the card needs more power, it uses the molex connector for additional 5V and 12V power. 3.3V is only carried in the slot.

That's what I had originally thought. Now to find out why--Why it needs 5v when the PCI-E does not.

PCIe is capable of 75W through the slot, AGP was 25W (roughly). AGP Pro could provide 50W to 110W depending on the version used.

There is a little bit on AGP Pro here: http://www.tomshardware.com/2000/09/22/agp_pro_/page2.html

The current AGP slot can supply up to 25 W to the graphics card. With the two additional pins, PRSNT1# & PRSNT2#, the AGP Pro cards report its power requirements to the motherboard. An AGP Pro slot can provide a total of 50W or 110W.

 

[computer]

Thanks for the info, I'll look into it.

 

[computer]

Well, I disconnected the red 5v line and my PC wouldn't boot. So obviously the 5v is indeed used and needed for AGP cards.

 

[Continuity28]

Originally posted by: computer
Well, I disconnected the red 5v line and my PC wouldn't boot. So obviously the 5v is indeed used and needed for AGP cards.

That's a shame.

I guess you'll need to use your multiple molex modular cable eh?

 

[amenx]

Just wondering, maybe not related though, but dont some cards have fan speed options? Like when its in 3d mode fan speed is 100%, and in 2d mode it slows down?

 

[computer]

Originally posted by: Continuity28

Originally posted by: computer
Well, I disconnected the red 5v line and my PC wouldn't boot. So obviously the 5v is indeed used and needed for AGP cards.

That's a shame.

I guess you'll need to use your multiple molex modular cable eh?

That, or either once again have to make something myself that no else makes! :disgust: The PS has TWO SATA modular cables, and I only need one of those, whereas with the 4-pin Molex cable I may end up needing both of those modular cables, I don't know now. If did end up needing both, that would defeat the purpose of having a dedicated video card power cable as most recommend. So I'd have to use one of the SATA modular cables and "adapt" it to the floppy type power connector needed by my video card....then that would defeat the purpose of the modular cable design and using fewer cables, just the cables you need! Has anyone ever seen an SATA power connector to a floppy power connector adapter? If not, I'd have to rig that.

I'm thinking about modifying the PCI-E power cable, somehow adapting/rigging it to accept the floppy drive type power connector on the card, then I'd have to get the 5v source from another source and attach that wire to the appropriate hole on the floppy type connector on the video card. This way, at least the 12v line to the card would be dedicated. For that it would help if I could find a PCI-E power cable to male floppy power cable adapter.

It would be great if I could find a female PCI-E power connector, like you find on PCI-E video cards, connect that to the PCI-E power connector cable from the PS, then coming out of the female PCI-E power connector I could have the 12v and G wires going to the video card, then get the 5v from elsewhere.

 

[jiffylube1024]

A 9800 Pro doesn't draw anywhere near enough juice to be worrying about running a dedicated line to the card. Just don't put all of your hard drives on the same line and you'll be fine.

Btw, I'm pretty sure AGP cards draw their power primarily from the +12V line, but it might need to "see" the 4 pins from the molex connector to think it's working. Modding a 6-pin PCI-e adaptor is not a good idea, just stick with the molex plugs direct from the PSU...

 

[computer]

Originally posted by: jiffylube1024
A 9800 Pro doesn't draw anywhere near enough juice to be worrying about running a dedicated line to the card. Just don't put all of your hard drives on the same line and you'll be fine.

Btw, I'm pretty sure AGP cards draw their power primarily from the +12V line, but it might need to "see" the 4 pins from the molex connector to think it's working. Modding a 6-pin PCI-e adaptor is not a good idea, just stick with the molex plugs direct from the PSU...

I haven't been able to find anything out regarding its current requirement, but it was either the manual or website that said a separate line is recommended for it, and said something to the effect of being recommended for "...any video cards that require separate power".

This card came out before there were split 12v rails, so I don't understand why that (dedicated/separate power cable) would be necessary current or wattage wise because the power comes from the 'same place' in a non-split PSU! So for this card, this makes me lean towards the school of "separate power cable recommended" possibly due to EM interference and not any current or wattage reasons. ?? Anyone have any thoughts on that?

Btw, I'm pretty sure AGP cards draw their power primarily from the +12V line, but it might need to "see" the 4 pins from the molex connector to think it's working.

How do you think it would "see" that 5v pin? Do you mean like the connector on the card is using some kind of impedance, capacitance or inductance "sensing" rather than actually needing the 5v voltage?

I guess one could always just use the PCI-E power cable than hook up a 5v battery to the 5v connector pin!

 

[computer]

Originally posted by: amenx
Just wondering, maybe not related though, but dont some cards have fan speed options? Like when its in 3d mode fan speed is 100%, and in 2d mode it slows down?

I haven't had enough experience with 3D or gaming to know that. I however never noticed any fan speed changes auditory wise on a 6800GT, or 7800GT; and on my AIW Radeon 7500 & AIW 9800 Pro I couldn't tell because I have so many fans in my case it drowns out everything! My guess would be that probably over the next 18 months or so when video card memory doubles again, and their RAMDAC's and core speed double again, a variable speed fan would probably become common place in the higher end cards like it has in CPU HSF units.