AGP 1.0, 2.0, 3.0, 1X, 2X, 4X, 8X

[Lunabjone]

Hello All,

I've been trying to get a grip on what they mean and how they are related. Sometimes I see AGP referenced with 1X, 2X, 4X, 8X other times its by 1.0, 2.0, 3.0. Speed vs Voltage? Other times I see 8X AGP 2.0 Required. Can they be more than one?

Thanks so much

 

[Aluvus]

1.0, 2.0, and 3.0 are different versions of the AGP specification itself. 1.0 introduced AGP 1x and 2x, 2.0 introduced 4x, and 3.0 introduced 8x. They made other changes as well (1.0 specified 3.3 V signaling, 2.0 added 1.5 V, and 3.0 added 0.8 V), but the increases in total bandwidth are the most well-known.

1x, 2x, etc. describe the capacity of the AGP link. AGP operates (always) on a 66 MHz clock signal. A 1x slot transfers data once per clock, and so operates at 66 MHz. 2x transfers data twice per clock (rising edge and falling edge of the signal), for an effective speed of 133 MHz. One convention for describing this is to say it performs 133 MegaTransfers per second (MT/s), which is clumsy but unambiguous. This is known as double-pumping. AGP 4x, then, engages in quad-pumping, transfering data 4 times in each clock cycle. This lets it execute 266 MT/s. AGP 8x is octo-pumped (or however one would say that), and so manages 533 MT/s.

The Wikipedia article on this topic is moderately helpful.

 

[Lunabjone]

Aluvus,

I think I understand it now. You've been very helpful. The Wikipedia link had some good info too.

Thank you

 

[Peter]

Also, AGP 2.0 substantially increased the power budget for the card.

 

[Lunabjone]

good to know.. thanks!

 

[ForumMaster]

Originally posted by: Peter
Also, AGP 2.0 substantially increased the power budget for the card.

indeed. and PCI-E increased it even further. i know this OT, but graphic cards keep on requiring more and more power. i suppose we will eventually have video card PSU.

 

[dguy6789]

Originally posted by: ForumMaster

Originally posted by: Peter
Also, AGP 2.0 substantially increased the power budget for the card.

indeed. and PCI-E increased it even further. i know this OT, but graphic cards keep on requiring more and more power. i suppose we will eventually have video card PSU.

http://www.anandtech.com/tradeshows/showdoc.aspx?i=2770