Infatuated with Itanium, Intel has long resisted the obvious: creating a 64-bit chip that simply extends the x86 architecture on which the company built its fortune. Instead, Intel has ceded that ground to AMD, whose 64-bit, x86-compatible Opteron has steadily eaten into the market shares of both Itanium and the 32-bit Xeon throughout the past year. For many, Itanium has been too expensive and too much of a departure. And Xeon has lacked the 64-bit headroom provided by Opteron.
The game changed in late June when Intel introduced its newest Xeon processor, code-named Nocona. Intel unveiled the most recent arrival in its storied Xeon processor line with little fanfare, but in fact, it’s a major departure given that Intel has actually adapted the x86-64 instruction set that AMD developed for the Opteron. Intel’s new architecture, the EM64T (Extended Memory 64 Technology), brings a Xeon chip into direct competition with the Opteron for the first time.
The newly released CPU will take awhile to make its mark in the 64-bit computing world because all x86-64 code written so far has been for Opteron. Software tweaks and optimizations are in order to permit recently developed x86-64 code to run on the processor. For example, the 64-bit beta version of Windows Server 2003 will not run on this chip, as it’s been coded for the Opteron and will not install if CPU detection fails to find Opteron. This will be remedied soon, no doubt, but similar issues will abound for some time. Similarly, Red Hat Advanced Server Update 1 will not install on an EM64T system, but Update 3 will because EM64T support has been added.
Downshifting to 32 bit
Lack of 64-bit support is the main reason I benchmarked the Nocona chip in 32-bit mode only, using a 32-bit Xeon system as a basis for comparison rather than an Opteron system. Given time and development effort, 64-bit benchmarks will be more accurate and will provide a clearer picture as to how Nocona measures up against Opteron in 64-bit performance. Nonetheless, I was able to install Red Hat Linux Advanced Server 3.0 for x86-64 Update 3 on our prerelease, Nocona-based Dell PowerEdge 2800 test system. A few new drivers were required, notably the MegaRAID2 driver for the PERC RAID controller. Otherwise, the installation was smooth and uneventful (see more on Opteron vs. the new EM64T-based Xeon).
Running strictly 32-bit code, I tested the new chip on Red Hat Linux Advanced Server 3.0 for i386. The Dell PowerEdge 2800 test system had dual 3.6GHz Xeon EM64T CPUs with 1MB of Level 2 cache, an 800MHz FSB (front-side bus), and 4GB of DDR2 RAM. The 32-bit Xeon contender was a Dell PowerEdge 2600 that had dual 3.2GHz Pentium 4 Xeon CPUs with 512KB of Level 2 cache, a 533MHz FSB, and 4GB of DDR RAM. For reference, I also ran the Linpack tests on a Hewlett-Packard ML350 with dual 2.8GHz Pentium 4 Xeon CPUs with a 400MHz FSB, 512MB of Level 2 cache, and 4GB of RAM. All tests were run with Hyper Threading disabled, and I ran all tests on the stock Red Hat 2.4.21-EL kernel (these numbers would probably improve with a v2.6 kernel).