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Ah, the old PCI versus AGP question. Everyone knows that AGP is faster, but the real world numbers would never show it. Until recently, the Voodoo3 2000 was the only Voodoo3 you could get for a PCI slot and probably the fastest PCI video card available. But now, 3dfx is offering the Voodoo3 3000 in PCI form. Being the curious and completely hardware-addicted types that we are, we decided to put the Voodoo3 3000 PCI through its paces and then compare its performance to that of a Voodoo3 3000 AGP. Not only would we get to know how good the Voodoo3 3000 PCI is, we would get to know whether AGP really makes a difference over PCI when using current hardware and software. AGP is faster than PCI theoretically, but does it actually show in the numbers? Inquiring minds want to know! So here we go, with a mixture of a PCI and AGP comparison as well as a 3dfx Voodoo3 3000 PCI review.

First, lets take a detailed (but understandable) look at the differences and similarities for graphics cards between PCI (Peripheral Components Interface) and AGP (Accelerated Graphics Port):

PCI, as it comes on mainstream mainboards, is a 32-bit wide 33MHz bus capable of 132MB/s theoretical maximum transfer rates. 32-bit pieces of data sent at a rate of 33MHz come to 132MB/s. There are 64-bit, 66MHz, and 64-bit 66MHz implementations of PCI as well, but mainstream PC systems do not use those other types so we will not discuss them any further.

AGP is a 32-bit wide 66MHz bus capable of 528MB/s theoretical maximum transfer rates. If you do the math, this only adds up to 264MB/s, which is AGP 1X. But AGP 2X cards transfer data on the rising and falling edge of the clock (like UltraSCSI2 and DDR RAM) which doubles the transfer rate. When AGP 4X is available, peak theoretical transfer rates will reach 1056MB/s. There is some confusion in the market as to what exactly AGP 2X is since it is commonly called 133MHz AGP.

So the AGP bus has four times the transfer rate of the PCI bus due to running at twice the clock speed as well as to its use of both the rising and falling edge of the clock to send data.