Linked by Amjith Ramanujam on Thu 31st Jul 2008 20:51 UTC, submitted by snydeq
Hardware, Embedded Systems While using an AMD Barcelona server to create a portable benchmarking kit, InfoWorld's Tom Yager discovered something unexpected: "I could incur variances in some benchmark tests ranging from 10 to 60 percent through combined manipulation of the server's BIOS settings, BIOS version, compiler flags, and OS release." Yager put this matter to AMD's performance engineers and was told he was seeing an effect widely known among CPU engineers, but seldom communicated to IT - that the performance envelope of a CPU is cast in silicon, but is sculpted in software. "Long before you lay hands on a server," Yager writes, "BIOS and OS engineers have reshaped its finely tuned logic in code, sometimes with the real intent of making it faster [...] sometimes to homogenize the server to flatten its performance relative to Intel's."
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RE: What are the implications?
by wdeviers on Fri 1st Aug 2008 13:21 UTC in reply to "What are the implications?"
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On a factory build machine, you would typically have to replace the BIOS. There are a lot of settings that the OS can't directly control. Think the deep magic stuff like memory timings, AGP memory allocation, bus speeds, CPU multiplier, etc.

Dell/HP/Apple/etc all come with heavily sanitized (or crippled) BIOS versions. They generally have the bear minimum options available to do whatever the machine is supposed to do. Boot order, basic power settings, BIOS password, that sort of stuff. The "enthusiast" machines come with basically no BIOS restrictions. On a good BIOS setup, you can change at least a dozen different memory timings alone; you can increment the bus speed 1Mhz at a time, or enable and disable specific features or optimizations.

Another difference is that the enthusiast boards take the time to figure out specialized performance work for the various chips while large factory OEMs won't bother because their goal is to minimize support calls. So if you buy a performance motherboard from DFI or Abit, they're going to not only have lots of options in the BIOS to tweak, they're also going to be using chipsets specifically designed to maximize performance of an AMD chip (or Intel). The factory guys just want to "make it work".

If you have that kind of board and can tweak with it, then both Linux and XP can run optimized for AMD hardware to a degree. In XP you can install the AMD processor driver. In Linux, it's built into the kernel already.

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