RPGDX > Forums > Off Topic > Computer question

MadQB · I wanna be a ballerina! Joined: 31 May 2002 Posts: 24

Hey all, I have been lurking for almost a year and a half without any posts here. Pretty much quit coding and surfing the indie forums ever since gdr went down. But lately I've been feeling the tug of the community and have been slinking around reading posts and project info and other things. Maybe some of you even remember me from like 2 years ago too.

Anyway, I just have a quick question about processor speeds vs bus speeds and things. Just wondering how one calculates the actual speed of the processor. I have heard a few different things. First off, i guess it is different on Pentium/intel based mobo's than amd based mobo's. Maybe you don't know what I mean. There is a clock multiplier, bus speed, ram bus speed and the max frequency of the cpu itself. Somehow we put all these together and find out what speed the system is actually running at. A tech guy has been talking about it lately but he fails to explain himself well enough, and I am just curious about the whole deal.

I mean, don't get me wrong I can understand almost any explanation you give me, I just need a thorough one that Describes both types (if a difference exists).
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Bjorn · Posted: Thu Feb 12, 2004 9:17 pm Post subject:

Hello lurker. I see all your previous posts have "fallen off the edge of the world", to quote Mr. Pumpkinhead, who I haven't seen here for a long time either. Sorry about that. :-)

MadQB · I wanna be a ballerina! Joined: 31 May 2002 Posts: 24

Bjorn · Posted: Sat Feb 14, 2004 1:48 am Post subject:

The multiplier setting used to be a jumper setting, and your motherboard manual would tell you which jumper to move where. Those were the days when I didn't even think about meddling with the system. Today, most motherboards will have this setting in their BIOS. As I said, you still might have to get back to the jumpers when you screw up your BIOS settings too bad. For example I tried overclocking my bus speed and moving the multiplier down, but my system didn't like that and wouldn't boot anymore until I reset the BIOS settings. Anything better than no message, and then the smell of your memory melting away a few minutes later. :-)

BTW, it says when you registered next to every post you make. You seem to have come in 2 days after me, I guess you were also already around before these forums got set up. :-) I was just apologizing for purging this forum of old posts and as a result only 2 out of your current 8 posts are present. I kinda regret it now, but at the time broadband wasn't in sight for me and I still wanted to download the database from time to time.

MadQB · I wanna be a ballerina! Joined: 31 May 2002 Posts: 24

Oh, thats alright, I'm just glad to be back now.

Anyway, I will check my manual, and if i find nothing i will check the bios again. Thanks for the help.
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valderman · Posted: Sat Feb 14, 2004 6:23 pm Post subject:

I'm kind of tired, so I don't know how well my answers apply to the original question, but anyway:
FSB (bus speed) * clock multiplier = CPU clock frequency. For example, my Athlon 64 is running at 200MHz FSB * 10 multiplier.
If you are running your memory synced with the FSB (which you really should be doing), the memory frequency will be 2 * FSB. The speeds of most components in your computer is somehow proportional to the FSB - raising it will improve performance, but decrease stability if you don't have high-quality components. For example, my cheap crap memory effectively puts an end to all of my OC attempts.

You can also change the clock multiplier to adjust the clock frequency of the CPU - this is useful to increase performance a little if your memory isn't fast enough to keep up with a higher FSB, or if your CPU can't take the higher clock frequencies, you can lower it while increasing the FSB and still get a significant performance boost. Sadly, many new CPUs come with their clock multiplier locked (I can only lower mine, not increase), to prevent overclocking.

A CPU doesn't really have a set max clock frequency - you can increase it to your heart's content, as long as the CPU can keep up. The max frequency can vary among different models of CPUs even within the same CPU family - for example, some Athlon XP 1700+ default to only 1.5V (or something like that) and can take really high frequencies, while others default to 1.6V and can barely be overclocked at all.

Finally, since you mentioned the "speed" of the CPU, you should be aware that the perceived speed isn't equal to the clock frequency (though you probably already know this) - different CPUs can execute a different number of instructions per clock cycle at varying speed depending on its pipeline construction.
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MadQB · I wanna be a ballerina! Joined: 31 May 2002 Posts: 24

valderman · Posted: Sat Feb 14, 2004 7:13 pm Post subject:

Well, the base FSB that is used to calculate the speed of everything else is 200MHz, the memory is working at 400MHz, though they have this technology called HyperTransport (which I don't know much about) that improves memory performance, much like DualChannel. Benchmark apps like SiSoft Sandra are totally clueless about this, and can produce some funny results - my memory is, for example, working at 378% of its maximum capacity. ^_^
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