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Old 05-22-2003, 01:06 PM   #1
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GCC has option for Xeon cpu ???

Hi all,

Does anyone know that the latest GCC version 3.4 has "-mcpu "option for xeon cpu???

Each time when I compile code using gcc or g77, it will read information from file "specs" . I read file "specs" and see there are a couple of cpu options in the files, such as i386,. i486 , pentium, pentiumpro etc, but there is no xeon. I use GCC 3.1 so far . so when I specify the "-mcpu=xeon" in the command line, it said xeon is bad value.

If GCC 3.4 has xeon cpu option in the file "specs" , then maybe I can specify "-mcpu=xeon" in the compile command line to test my slower code on xeon machine. Check my previous thread if you have interest on my codes running slower on xeon machine who has higher speed and more memory.

By the way, what is the use of file "specs" ? I don't understand this file completely.

Any idea ???? Thanks to all of you in advance.

Old 05-22-2003, 01:56 PM   #2
Registered: Mar 2003
Distribution: Debian
Posts: 275

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I don't follow the processors much, but aren't the Xeon cpus just like their "desktop" versions, except a bigger/faster cache? Perhaps "rated" for SMP configs?

There isn't much for the compiler to optimize there. It's more up to your code to stay in the cache size. I believe (you should probably read the gcc mailing list archive for real info) that the cpu optimizations done are things like using newer instructions, or changing instruction order to keep the pipelines filled.

You would be better off looking at the '-f' optimizations (-funroll-loops vs. -funroll-all-loops) to see what runs faster on different cpus.

Oh, on reading your previous post, isn't a Xeon 1.8 a Pentium IV? vs. a PIII 1.0. I think they are about the same speed. Try compiling the code twice, once with -march=pentium3, and with -march=pentium4. Try to see any difference there.

The specs file is basically a preprocessor for options. If you needed to which C library got used, you could do it here.

Good luck,


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