AGP Core Voltage

[GForceYourHand]

I just got a motherboard whose manual says it can only run AGP cards running at 1.5V. Does that mean AGP 4x cards? How do I know what voltage an AGP card runs at? I want to buy an older card for this PC for the time being until I can afford a real good one and it's hard to find specs on older cards.

 

[priyajeet]

AGP [Accelerated Graphics Port] is a Point-to-Point [Chip-to-Chip] bus using 1.5 Volt or 3.3V signaling. The main use of the AGP bus is as a Local Video bus in IBM compatible Personal Computers [PCs]. The AGP bus is based on the PCI [Peripheral Component Interface] spec, using the PCI specification as an operational baseline. The AGP specification adds 20 additional signals not included in the PCI bus. The AGP specification defines the Protocol, Electrical and Mechanical aspects of the bus.

The Mechanical definitions include a connector and Add-in card. The Card sizes and 1.5v and 3.3v connectors are also defined with in the spec. There are five connectors defined: AGP 3.3v, AGP 1.5v, AGP Universal, AGP Pro Universal, AGP Pro 3.3v, and AGP Pro 1.5v. PCI and AGP boards are not mechanically interchangeable.

The AGP 1.0 specification defined 1x and 2x speeds with the 3.3v keyed connector.
The AGP 2.0 specification defined 1x, 2x and 4x speeds with the 3.3v, or 1.5v keyed connector or a 'Universal' connector which supported both card types.
The AGP Pro specification defined 1x, 2x and 4x speeds with the 3.3v, or 1.5v keyed connector or a 'Universal' connector which supported both card types.
The AGP 3.0 specification defined 1x, 2x, 4x and 8x speeds with the 1.5v keyed connector or a 1.5v AGP Pro connector.
Each up-grade is a supper-set of the 1x mode, so 4x will also support 1x. The base clock rate is 66MHz, but to achieve to 2x, 4x, and 8x speeds the clock is doubled each time. AGP uses both edges of the clock to transfer data.

AGP (1x): 66MHz clock, 8 bytes/clock, Bandwidth: 266MB/s [3.3V or 1.5V signal swing]
AGP 2x: 133MHz clock, 8 bytes/clock, Bandwidth: 533MB/s [3.3V or 1.5V signal swing]
AGP 4x: 266MHz clock, 16 bytes/clock, Bandwidth: 1066MB/s [1.5V signal swing]
AGP 8x: 533MHz clock, 32 bytes/clock, Bandwidth: 2.1GB/s [0.8V signal swing]

The AGP data bus may be 8, 16, 24, 32, or 64 bits. Due to timing requirements the maximum bus length is 9". The trace impedance is specified as 65 ohms +/- 15 ohms (no termination resistor is specified). For the 8x speed the bus requires a parallel termination.

<b>TAKEN FROM http://www.interfacebus.com/Design_Connector_AGP.html

Do google search for all these kind of things.</b>

<i> <font color=blue>Futile is resistance,</font color=blue><font color=red> assimilate you we will.</font color=red> </i>
<b>Hard work has a future payoff. Laziness pays off now.</b>

 

[Crashman]

BS, AGP2x is 66MHz clock. AGP4x is 66MHz clock. AGP8x is 66MHz clock. They just use a method similar to DDR, QDR, and ODR to double, quadruple, and octuple data rates.

All he really needs to know is that all AGP8x boards support both 8x cards and 4x cards at full speed, and that all AGP4x boards support 4x and 8x cards at 4x speed, regardless of what the maker says about voltage.

And he should also know the reason they say 1.5v only cards is because 3.3v cards won't work, it has no bearing on 0.8v signals.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[davemar14]

Yup. My GeForce 2 Ti, won't work on my Asus A7N8X Deluxe. It will run on my 2nd comp with a AGP 4x slot, but not on my Asus board with the AGP 8X. I must have a rare GeForce2 with 3.3V and not 1.5 V. I just use a GeForce4 on my Asus board.

 

[Crashman]

I remember a site had a list of such cards a few years ago. "AGP4x" cards that didn't meet AGP2.0 specification, even though they were keyed for both.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[priyajeet]

Can be BS, I just took it from a website.
Well <A HREF="http://www.abit-usa.com/products/graphics/documents/agp30_final_10.pdf" target="_new">This</A> seems a better document about it.

<i> <font color=blue>Futile is resistance,</font color=blue><font color=red> assimilate you we will.</font color=red> </i>
<b>Hard work has a future payoff. Laziness pays off now.</b>

 

[Crashman]

Shortcuts in the previously refered document would confuse the reader. And them calling it clock rate instead of data rate should have been caught by a fact checker. Best to refer to only the needed facts when dealing with someone who doesn't know these things. The whole KISS phillosophy. That's why I just keep these simple things in mind:
1.) All AGP8x cards are 3.0/2.0 cross compliant.
2.) Most AGP8x cards have been 3.0/2.0/1.0 cross compliant
3.) All AGP4x cards have been 2.0/1.0 cross compliant
4.) Motherboard manufacturers only say 1.5v to mean their boads are not AGP 1.0 voltage signal compliant.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[priyajeet]

got it, but that was directed towards u. i mean i replied to u.

<i> <font color=blue>Futile is resistance,</font color=blue><font color=red> assimilate you we will.</font color=red> </i>
<b>Hard work has a future payoff. Laziness pays off now.</b>

 

[Crashman]

Yes, well, my BS comment wasn't directed towards what you said, but what the people who wrote the technical information said. Most technical information I find is either incomplete, misstated, or misleading.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[addiarmadar]

Either look in the manual or in your bios. It should give you a way lock lock the bus to 2x, 4x, or 8x.

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