The ACorp 4VPX266A features both multiplier and FSB adjustments but no voltage manipulation options. You can select up to 132MHz FSB in 1MHz increments and the multiplier goes up to 23x. The Shuttle AV40R however, features a max FSB of 160MHz in 1MHz increments, multiplier settings up to 23x, CPU voltage, DDR voltage and chipset voltage adjustments. This plethora of overclocking options included by Shuttle competes with even the likes of Asus and Abit. Since the Pentium 4's multiplier is locked, the highest we could stably overclock our 2GHz CPU to was 2.2GHz (20x110MHz). Both boards were completely stable at this speed and I was able to run Prime95 on each of them for 24 hours without crashing. I am fairly happy with this 10% overclock however, clearly we can see that both boards have the potential to go much higher.
The Shuttle AV40R has an MSRP price of $US119 while the AV40 has an MSRP price of $US99. Since the ACorp 4VPX266A is not yet on the market, its price is not available. As a comparisson, Abit's TH7II-RAID motherboard based on the Intel i850 chipset is retailing for around $US220. A stick of Mushkin 256MB PC2100 DDR SDRAM sells for $US64 while 256MB of Mushkin PC800 RAMBUS sells for $US129. As you can see from the above prices, purchasing a P4X266 based system will save you a lot more money when compared to purchasing an i850 based system.