ATi designed the 256 MB variant of the X1 primarily for OEM customers. It is based on the FireGL 9700 chip - a descendant of the Radeon 9700. An additional power connector (a type typically found on hard drives or CD ROM drives) is not found on this particular graphics card. Instead, the power is supplied through the AGP Pro slot. Therefore, those who are interested in the card should be careful to check and see whether or not their motherboard actually has an AGP Pro slot!
A special feature of this model is that it takes up two slots in the PC system. Essentially, this is due to the large cooler on the card. As a point of comparison, this is not to be found on either of the 128 MB versions. There's not much to be expected from the benchmarks. We determined that there were practically no differences between the results of the X1 128 MB and those of the X1 256 MB. The reason for this lies with the test programs, themselves. At the moment, most of the applications are not yet ripe for 256 MB. Only certain special applications can make use of the extra performance. If you still want to go with the FireGL X1 256 MB, be prepared to fork over $200 more than you'd pay for the 128 MB model.