Some basic computer questions...

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DaMaDo

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May 31, 2001
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A buddy has been asking me all sorts of questions on the relation of computer components and it made me realize I don't know some of the fundamentals. Here are some of the questions I was asked that I wasn't really sure of:

1. Ok so we have FSB speed for the CPU, and mhz for ram....how do these relate?

2. If you have a 1 GHz FSB AMD venice cpu and pc3200 ram running at 400 mhz, is the ram slowing down everything to 400 mhz?

3. Why pay more for a faster FSB or RAM mhz?

4. How does FSB or ram mhz relate to southbridge/PCI/AGP?

Thanks =)
 
Ok maybe it's better to ask this:

Where can I go to learn what front side bus is and how RAM MHZ affects the speed of the computer as a whole etc...
 
Front Side Bus speed desribes the clock rate at which the connection between the memory and the CPU operates. It only applies to certain architectures and is often mistakenly transposed on other technologies (Hypertransport for one). Some things are similar, others are quite different. Overclockers have to care about the difference, most users don't.

The FSB clock is also the one on which the CPU speed and memory speed "hang" in the architectures where it applies, so the memory will run at the FSB speed or at a ratio to it. The CPU will run at a multiple of it. So altering the FSB clock effectively also overclocks the memory and the CPU (however if you install a CPU that's meant to run at the higher FSB already, no dice).

Uhh...HT on A64 is different because of the on-chip memory controller. The CPU clock becomes the base instead of the FSB and the memory becomes dependent on it according to a divider that's calculated more or less in the background.

FYI, Venice CPUs come in speeds down to 1.8GHz. Also PC3200 doesn't run at 400MHz, it runs at 200MHz. It's also refered to (confusingly labeled by marketing types and overenthusiastic engineers) as DDR400. If you remember old school SDRAM, DDR or more properly DDR SDRAM - Double Data Rate SDRAM, is basically SDRAM that they realized they could use both edges of the clock signal to send data on. So functionally it's as fast as if it was SDRAM running at double the speed, so they slap the 400 on there to push sales and look pretty. Anyway the two clocks are pretty independant on the A64, or rather there's such a wide variety of ratio choices that you can run the CPU with a pretty high overclock without ever moving the memory more than a smidge off 200MHz.

Why pay more for a faster FSB or RAM mhz? Well because it's FASTER. :D It depends a lot on what the system needs to do...if I gave you the fastest supercomputer in the world and all you wanted to do was check your email and blog a bit, all that extra power wouldn't do you one lick of good past the amount you actually had a use for. SO it really depends what you're doing.

How does FSB or ram mhz relate to southbridge/PCI/AGP? Not much at all. Well, hopefully. Depending on the architecture and on the quality of the implementation, sometimes overclocking the FSB inadvertantly overclocks a bunch of other things...good motherboards have a "lock" that fixes them at the speed they're supposed to operate at. You don't really want to overclock the PCI bus wholesale, because not every card you have installed is going to like it very much....

Any questions? ;)
 
DaMaDo said:
A buddy has been asking me all sorts of questions on the relation of computer components and it made me realize I don't know some of the fundamentals. Here are some of the questions I was asked that I wasn't really sure of:

1. Ok so we have FSB speed for the CPU, and mhz for ram....how do these relate?

2. If you have a 1 GHz FSB AMD venice cpu and pc3200 ram running at 400 mhz, is the ram slowing down everything to 400 mhz?

3. Why pay more for a faster FSB or RAM mhz?

4. How does FSB or ram mhz relate to southbridge/PCI/AGP?

Thanks =)
Click to expand...


1) FSB is also suppose to be indicate in mhz. it's the frequency of the FSB or the RAM speed.

2) no. but will still cause the whole system to be slower

3) coz to be faster

4) do sound much related. Totally different topic
 
Thanks a lot for the replies. One more question....well let me see if I understand this. If I have a 1 GHz FSB and my ram is PC3200...it doesn't slow the whole memory to CPU speed to 200 mhz right? What if I had pc2700 or PC4200?

It was mentioned that the CPU works on a multiplier...so is it 200 x 5 = 1ghz? That kind of thing? Which would mean that pc3200 at 200 mhz is perfectly matched? How would 400 mhz ram make this faster? it would make the CPU work at 400 x 2.5? If that's true then its not really faster just a diff ratio....I'm lost =/

This is where I really get confused and all the FAQs don't seem to explain those relations.
 
Your sig says you have an A64 FX-53 so you don't have a front side bus, you have a hypertransport link. Main difference is that the memory speed hangs from the CPU instead of the memory and CPU speed hanging from the FSB.

For A64 the memory isn't going to affect the CPU speed. At all. Because the CPU speed comes first and the memory operates at some divider of it...2GHz / 10 for 200MHz (aka DDR400, aka PC3200) for example.
 
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