AGP 8X in 4X Slot?

[Erin Peterson]

Hi all,

Just a quick question about AGP slots.

Could I put a 8X AGP video card in a 4X slot and have it function at 4X
speeds? The reason I ask is that I would like to buy a new video card
but the card I want is 8X and I don't have the resources to upgrade my
MoBo.

Any help would be greatly appreciated.

TIA,
Erin

 

[kony]

Hi all,

Just a quick question about AGP slots.

Could I put a 8X AGP video card in a 4X slot and have it function at 4X
speeds? The reason I ask is that I would like to buy a new video card
but the card I want is 8X and I don't have the resources to upgrade my
MoBo.

Any help would be greatly appreciated.

TIA,
Erin

Usually yes. I vaguely recall some ATI cards might not
work, you'd have to check their website per the specific
model to see if that is an issue.

 

[w_tom]

The motherboard must be compatible with the 8x video
hardware. 8x AGP uses different signaling voltages compared
to 4x. There is a handshaking between motherboard and video
card so that the correct signaling voltages (1.5 or 0.8 volts)
are used. If your motherboard does not support these lower
voltages for 8x AGP, then motherboard might put excessive
voltages into the video card - damage the video card.

 

[Larc]

| The motherboard must be compatible with the 8x video
| hardware. 8x AGP uses different signaling voltages compared
| to 4x. There is a handshaking between motherboard and video
| card so that the correct signaling voltages (1.5 or 0.8 volts)
| are used. If your motherboard does not support these lower
| voltages for 8x AGP, then motherboard might put excessive
| voltages into the video card - damage the video card.

That's a bit strange. Why would most 8x video cards be backward
compatible with 4x if they worked only in 8x-capable boards? Wouldn't
that be a worthless compatibility if 8x cards couldn't be mated with
4x boards?

Larc



§§§ - Change planet to earth to reply by email - §§§

 

[DaveW]

Yes, it will run at 4x.

 

[w_tom]

I did not know that 4x motherboard slots did not support 8x
boards. But the Intel specs for 8x boards is quite specific.
The motherboard must provide a different voltage for 8x
boards. Notice the voltages provided. 0.8 and 1.5. Why? We
had an AGP board that we suspected was being destroyed by
motherboard. We measured those voltages. And yes, also
provided is a voltage that is the threshold for a logic one
and logic zero. If I recall correctly, the threshold voltage
even in Intel specs says 0.35 for 8x AGP boards and 0.75 for
4x AGP boards. Motherboard provides these voltages. Scary
how complex motherboard hardware has become.

I cannot report more. I do not have the data sheet with
maximum voltages for those 8x graphic chips. But the 8x board
does require lower voltages - 0.8 volts. 4x boards requires
1.5 volts. An AGP socket must identify the video board - and
adjust voltages accordingly. The data sheets say that quite
bluntly.

Again, I did not know any motherboard existed that could not
adjust voltages for 8x Graphics cards. Sockets are
mechanically different for earlier versions AGP graphics cards
because later earlier motherboards could not provide the 1.5
volts required by 4x AGP boards.

 

[YanquiDawg]

I definitely ran my FX 5900 4x/8x in a 4x motherboard.The board was the Epox
8kha+.

 

[allindelille]

This is only a test

I did not know that 4x motherboard slots did not support 8x
boards. But the Intel specs for 8x boards is quite specific.
The motherboard must provide a different voltage for 8x
boards. Notice the voltages provided. 0.8 and 1.5. Why? We
had an AGP board that we suspected was being destroyed by
motherboard. We measured those voltages. And yes, also
provided is a voltage that is the threshold for a logic one
and logic zero. If I recall correctly, the threshold voltage
even in Intel specs says 0.35 for 8x AGP boards and 0.75 for
4x AGP boards. Motherboard provides these voltages. Scary
how complex motherboard hardware has become.

I cannot report more. I do not have the data sheet with
maximum voltages for those 8x graphic chips. But the 8x board
does require lower voltages - 0.8 volts. 4x boards requires
1.5 volts. An AGP socket must identify the video board - and
adjust voltages accordingly. The data sheets say that quite
bluntly.

Again, I did not know any motherboard existed that could not
adjust voltages for 8x Graphics cards. Sockets are
mechanically different for earlier versions AGP graphics cards
because later earlier motherboards could not provide the 1.5
volts required by 4x AGP boards.

 

[allindelille]

Test

Usually yes. I vaguely recall some ATI cards might not
work, you'd have to check their website per the specific
model to see if that is an issue.

 

[General Schvantzkoph]

Hi all,

Just a quick question about AGP slots.

Could I put a 8X AGP video card in a 4X slot and have it function at 4X
speeds? The reason I ask is that I would like to buy a new video card
but the card I want is 8X and I don't have the resources to upgrade my
MoBo.

Any help would be greatly appreciated.

TIA,
Erin

Just check the specs on the card, most 8X cards will work fine in
a 4X slot. I'm running an 8X card in a 2X slot, works fine.