Here's what Anand said in his
P4 review:
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Along with the Pentium 4 Intel is introducing support and a need for the new ATX 2.03 specification. This specification basically makes room for the mounting holes for the Pentium 4?s heatsink retention mechanism in the case. This unfortunately means that current cases, without modifying the motherboard tray, won?t work with the Pentium 4 with its heatsink attached. If you?ve really got a lot of money invested in your case you can try and make your own mounting holes by lining up your motherboard and making the appropriate marks to drill through on the tray.
The next big change is with the power supply. The ATX 2.03 spec calls for an ATX12V power supply which supports the additional power connector required by i850 boards. This additional +12V power connector allows for additional power to be supplied to the motherboard around the CPU. With CPUs increasing in clock frequency and drawing more and more power, this helps to keep things stable in an area of the motherboard where current draw is at the highest levels.
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