Topic: Video Cards
Date: October 6th, 2004
Product: Radeon X600 PRO
Provided by: ATI Technology
Author: Kevin Elliott

Introduction

When ATI announced the launch of the R420 core developed under the project name Loki is one of the major deities in the Norse pantheon. He is a son of the giant Farbauti ("cruel striker") and the giantess Laufey. He is regarded as one of Aesir, but is on occasion their enemy. He is connected with fire and magic, and can assume many different shapes (horse, falcon, fly). He is crafty and malicious, but is also heroic: in that aspect he can be compared with the trickster from North American myths. The ambivalent god grows progressively more unpleasant, and is directly responsible for the death of Balder, the god of light.  It was not a complete revision of past cores but instead the Radeon X600 has the feature set and hardware support as the very popular Radeon 9600XT.

Both the X600 and 9600XT use the same four pixel pipeline architecture and include two programmable vertex shader pipelines.  The clock speeds are similar at 500 MHz but the memory speed of 740 MHz for the X600 as opposed to 600 for the 9600XT makes them slightly different in that area. But since we are dealing with the X600 PRO we should discuss the actual clock frequencies on this particular card. The X600 PRO is slower on both the front and back-end seeing how it only clocks in at 400 MHz for the core and 600MHz (300DDR) for the memory.

The Difference between AGP and PCI Express

So what's the big difference between AGP and PCI Express? In the simplest of terms it can be explained using a highway traffic analogy. Think of AGP bus as a one way street that is forced to move traffic in both directions at the same time and the maximum speed limit has been set to 2.1 GB/sec.

PCI Express uses two uni-directional links, one for upstream transfers and one for downstream transfers. For PCI Express x16, each link consists of 16 lanes, providing a peak theoretical bandwidth of 4 GB/sec in each direction. Thus, PCI Express offers significantly higher bandwidth in both the upstream and downstream directions than AGP 8X. Furthermore, it supports full duplex transfers (i.e. both directions simultaneously), while AGP can only support transfers in one direction at a time. Note that this important capability is only supported in native PCI Express designs.

The next thing that will separate the two type of video cards will be connectors used to mate them with your motherboard. I'm sure most of you are familiar with what an AGP slot connector looks like but have you seen an AGP slot connector side-by-side with a PCI-E x16 slot connector? Maybe not so here goes.