Sorry this is not entirely Linux related bar the fact that I will be installing Slackware to the machine in question.

I rashly purchased a bargain Shuttle SD30G2 case/mobo on ebay thinking I had an old CPU/RAM/HDD lying around. Anyway I cannot find the CPU I thought I had and am now looking at the options on ebay.

Shuttle say this board supports 800/1066/1333Mhz processors. Chipset Intel 945GC however looks to have a system bus up to 800Mhz.

Whatever CPU I purchase it will cost very little. But the internet has me totally confused.

If I go with a 1333Mhz CPU some "experts" say the multiplier is locked, and with FSB at 800Mhz the CPUs clockspeed would effectively decrease, ie. 9x multiplier CPU 3ghz/1333 would actually run at 2ghz/800. Is that true?

I am better off going with an equivalent clockspeed 800Mhz chip? If not then cache size is going to edge me towards core2duo e8xx. Otherwise I think a e5xx may be my best bet.

I would say to be safe, yes, get the fastest 800 MHz bus processor you can. I have never had one of these Shuttle boards to know if they truly do have support for the faster bus speeds (I know there were MB makers that hacked in support for that to the various 945 chipsets).

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i would check "tom's hardware" and even ask the question there. there are some knowledgable pc hacks there

i would say it depends on the bios. your faster CPU can likely be set to a slower speed (core2 supports frequency changes: but does the BIOS?)

i would also say go with the "better / faster CPU", it's a better bet the bios will let you change frequency and voltage (carefully!!!), and a "better cpu" runs cooler and faster at a lower speed than an older cpu

you can always find the motherboard manual online, and Intel cpu white sheet.

or you could go to "tom's hardware", it's a fun site

OH! note i never said any chip works on that MB. i have no idea. check the manual for socket and cpu support. sometimes a newer cpu can be put on a socket SOMETIMES NOT (not unless the bios has been upgraded).

there's a real chance of your getting a "no boot" situation if you don't check into it further.

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As X-LFS-2010 mentioned, it is the socket that determines which cpus the mobo will work with. Some sockets have a different designation, but are physically identical to other sockets. However, they are not electrically identical. So, just because a processor will fit in the socket does not mean it will work.

Your socket is LGA775, or socket T.

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Thanks all.

The Motherboard/Case is a Shuttle SD30G2.
Shuttle explicitly say it supports 800/1066/1333 on the site.
Furthermore I saw there were BIOS updates up to 2012.
Together that seemed like a good bet that there was support for later LGA775 processors.

I got an e7500 for 2 GBP, popped it in. (Shuttle make it so easy...the heatsink design is great!)
And I can now report back.

CPU is identified and works perfectly at defaults (266Mhz 11x Multiplier).
Furthermore BIOS supports frequency change, although the multiplier can be decreased in the BIOS it cannot exceed the default.
While the multiplier might be considered "locked" (it can still be decreased) frequency is not.

I'd therefore assume that e8xx CPUs would be just fine (max freq is something odd like 357Mhz).
CPUs with stock 800Mhz could theoretically be overclocked the most with their higher multipliers although I guess most people interested in this are probably not running such old hardware.