As a Xeon, Nocona is a honey of a power boost: fat cache; fast clock speed; smaller, denser die; and faster front-side bus. Intel's engineers busted hump to make Nocona Intel's best Xeon CPU. It's a shame that this laudable effort will be overshadowed by the last-minute inclusion of EM64T, Intel's 64-bit extended memory architecture. The Nocona EM64T-equipped server CPU, and its desktop counterpart Prescott, are precisely the "64-bit instructions strapped to 32-bit CPUs" that Intel warned against when Pentium 4 Xeon was launched.
Were EM64T sold for what it is -- x86 with a wider address bus and larger register set -- I'd have no complaints. But Intel hopes to use EM64T to blunt the market's growing interest in genuine 64-bit value servers and power desktops. These aren't waiting around the corner. They're here now, constructed around Advanced Micro Devices Athlon 64 and Apple Computer/IBM/Motorola PowerPC technology. But make no mistake: a 64-bit system requires a new system architecture (as AMD and Apple have created), not a new processor.
What characterizes a 64-bit system? Multiple independent I/O busses, on-chip memory controllers, and very highly integrated peripheral chip sets that eliminate the need for the many discrete single-purpose chips common to PC designs -- along with the slower, noisier circuits between them. Sixty-four-bit systems are technically simple compared with PCs' convoluted, legacy-bound designs. It took AMD several years of obsessive engineering to create Hammer (the former codename for the Athlon 64/Opteron line).
So here we have Nocona, Intel's would-be placeholder. Intel said in advance that it doesn't believe in this architecture. Neither do I. Nocona is, at best, a 32-bit Opteron emulator. Nocona will do well enough on 32-bit published benchmarks for a while. But during the next six to 12 months, while operating systems and I/O-intensive apps start flipping the 64-bit switch, users who already have true 64-bit AMD and G5 systems will get the total performance designed into these architectures. Those with EM64T systems will get what Intel designed into their systems, too. Why, they'll ask, didn't someone tell them nothing would happen when they flipped Nocona's 64-bit switch? Isn't it fun to know something that others don't?