Any voltage issues running an AGP 4x/8x card on an old 2x/4x m/b?

[Quick1]

Speedwise, the card will just drop down to 4x?right? Also, would a 4x/8x card also drop down to 2x, if needed? I want to run a CHAINTECH SA5500T2 Geforce FX5500 on an ASUS P3V4X. This board has the VIA Apollo Pro133A chipset but the manual does not specify the AGP voltage. By checking the hardware monitoring temps in the bios, I think its 5.0v. Currently running a GeForce 2 GTS AGP-V7700 but it?s quickly going south. I?d like to get a DirectX 9 AGP card for surfing and light gaming for less than $100 that won?t present a voltage problem to this old m/b. Also, anyone know the AGP voltage requirement of this card or any nVidia FX5500 card? Any feedback?

 

[Quick1]

Or...should I buy a PCI Express card and just use the PCI function untill I can ugrade the m/b?

 

[LTC8K6]

All AGP slots use a 5V supply.

The differences are in the signaling voltages which can be 3.3, 1.5, or .8V.

A modern 4X/8X card will be 1.5/.8V and work correctly in either slot.

A 2X/4X board may not be compatible with a modern 4X/8X card.

The board should switch to the 4X and 1.5V when you put the FX5500 in and it should work properly, but there are boards out there where it won't, and I am really not sure how you can tell.

There was a keying system for cards that were incompatible so they would not fit, but that is well in the past, I think.

 

[LTC8K6]

PCI & PCI-Express are incompatible.

I believe PCI FX5500's are still available.

 

[Quick1]

Good info LTC8K6! Agreed the PCI version is still available. But, would I be giving up speed by going from an AGP 2x GeForce2 GTS to a PCI FX5500?

 

[LTC8K6]

If we can determine that the board will do 4X and 1.5V, then the AGP card should work.

I am not sure if you would be giving up any speed going to a PCI card.

 

[LTC8K6]

I am getting a lot of folks saying that the board is unstable at AGP 4X anyway.

It might be better to just use a PCI card in that board, unless someone else can come up with a definite answer about the AGP port.

 

[Quick1]

Yes...I've heard the same thing.

Hmmm....maybe having a DirectX 9 vid card is not as imperative as I thought.

 

[Steve]

Originally posted by: LTC8K6
All AGP slots use a 5V supply.

Wrong. AGP supply voltage was, is, and will always be 3.3v

Signalling voltages:
1x/2x = 3.3v
4x/8x = 1.5v

8x has a "reduced swing" 0.8v available. In addition, "Universal" 2x/4x slots can handle a card that complies with either standard.

So if a card is AGP 3.0 (8x/4x) then it only needs to be compatible with that (1.5v). Further backward compatibility is optional and not often used. What this means is that while it can work in an AGP "Universal" slot (2x/4x) due to its 4x (1.5v) compliance, said card will not work in a 3.3v only (2x) slot.

Yes, they are often keyed to prevent incompatible voltages from mixing, but that wasn't 100% foolproof - some cards, and some slots, were keyed "Universal" but didn't comply with both voltages. Best to read up on each chips specs to be sure.

BTW, there is only one PCI-E chipset (at least that I know of) that has both PCI-E and AGP 8x, and that is the ULi M1695. Other boards with PCI-E and AGP can only support older, slower AGP standards.

 

[Quick1]

Oh, I thought the 3.3v was for the SDRAM memory. Does the memory also run at 3.3v?

I know this m/b is supposed to support AGP 4x because ASUS posted a registry key with this label on their website several years after the board was sold.

?AGP 4X turn on Registry key for VIA 694x N.B. in Windows 95/98/ME/NT40/2000?

sm8000: Point taken, so I should not assume a 4x/8x card will work in a 2x/4x slot. And the slot could even fry the card!

So...I guess I should go the PCI route as previously suggested. I?m considering this one, on the rig below. Any other card suggestions?

http://www.newegg.com/Product/Product.asp?Item=N82E16814145087



PIII@933
ASUS P3V4X m/b 1006.004
512MB ram
ASUS GeForce2 GTS AGP-V7700 32MB (2x only)
40GB IBM "DeathStar"
Win98SE

 

[Steve]

No, just do some research. What you need to find out:

Does this slot labeled "Universal" (2x/4x) actually properly support 4x's 1.5v? For this you need to go to the chipset maker's website and look up the chipset. Can't hurt to go to the boardmaker's website afterward.

Does this card labeled AGP 3.0 (4x/8x) really do AGP 4x's 1.5v? Again, look up the video chip itself, followed by the card maker too.

In my opinion, the most likely answer to both questions is yes. But look them up to be sure!

Not sure about the memory voltage, but that can also be looked up. A lot of things have run on the 3.3v rail over the years, some have moved to the 5v and even to the 12v too.

 

[LTC8K6]

I am pretty sure the AGP supply is 5V, but you could be right sm8000. My point was that the voltage in question is not the supply voltage.

I believe the AGP 8X spec requires 4X and 1.5V compatibility.

Actually, the AGP2.0 pinout seems to use 12, 5, and 3.3V lines in additon to the 1.5V.

 

[Steve]

The AGP supply voltage is definitely 3.3v, I can promise you that. I wish Intel (AGP is their baby) would keep their spec docs online, but I remember looking for them last year when I was temping at VisionTek and a customer had a question about using a card in an AGP Pro slot. All the searches resulted in PCI-E pages, and the AGP Forum's site was down then too.

Anyway, AGP 8x does indeed mandate 4x capability, and Universal slots mandate 4x compliance too. So if both components meet in the middle he's good to go. There are rare cases where an 8x card will support 2x's 3.3v standard but this is not mandatory and not often done.

If I remember correctly, the offenders who made Universal hardware but without supporting the voltage were old TNT or TNT2 cards and old Intel chipsets, but there may be others too, in both cases.

 

[Quick1]

Thanks for the feedback guys!

Alright, I'll do some more research before making a decision.