FSB, channel between CPU and system?

[VIAN]

"The FSB (or, for AMD processors, the HTT*), or Front Side Bus, is the channel through which your entire system communicates with your CPU. So, obviously, the faster your FSB can run, the faster your entire system can run." - Overclocking Guide

This is incorrect.

The FSB is the channel between the CPU and the memory controller.

So increasing the fsb cannot make your system run faster. The only thing you would be able to do is increase the communication between the RAM and CPU, that is if you have a 1:1 ratio.

The rest of the system runs on a PCI bus. This baby runs at 33Mhz which comes from dividing the FSB. Since modern mobos include a PCI lock so that when you increase the FSB, the PCI speed doesn't increase, because of stability issues, no matter how high your FSB is, you PCI bus, a.k.a. the rest of your system, will still run at the same speed.

 

[miketheidiot]

Originally posted by: VIAN
"The FSB (or, for AMD processors, the HTT*), or Front Side Bus, is the channel through which your entire system communicates with your CPU. So, obviously, the faster your FSB can run, the faster your entire system can run." - Overclocking Guide

This is incorrect.

The FSB is the channel between the CPU and the memory controller.

So increasing the fsb cannot make your system run faster. The only thing you would be able to do is increase the communication between the RAM and CPU, that is if you have a 1:1 ratio.

The rest of the system runs on a PCI bus. This baby runs at 33Mhz which comes from dividing the FSB. Since modern mobos include a PCI lock so that when you increase the FSB, the PCI speed doesn't increase, because of stability issues, no matter how high your FSB is, you PCI bus, a.k.a. the rest of your system, will still run at the same speed.

Thats interestsing because I thought the FSB went to the northbridge.

Anyways if you think a larger FSB won't result in a faster computer clock for clock, you must be an idiot. I'll dig up my old Axp benchies if you want proof.

 

[VIAN]

Sir, I believe you're the idiot.

No, I never said that, just pointing out what the FSB is because people seem to be confused about what it is. And I never said that you wouldn't gain any performance. Here is a quote from my previous post:

The only thing you would be able to do is increase the communication between the RAM and CPU, that is if you have a 1:1 ratio.

Increased communication means increased speed. But not to the system, just the RAM.

 

[VirtualLarry]

Traditionally, "front-side bus" meant the connection between the CPU bus and the system chipset. (Which for most chipsets, was further divided into two parts, the "north" bridge, which handled higher-speed components, like the CPU FSB, memory-controller, and then it had a connection to the "south" bridge, which handled lower-speed peripherals, like the PCI bus, ISA bus, IDE ports, LPC I/O, etc.). This came about during the Slot-1/PII era, because the off-die L2 cache was located on the CPU's "back-side bus" - a dedicated bus specifically for the L2 cache.

So that brings about an interesting question - on newer CPUs which no longer have the memory-controller embedded into the northbridge, but in the CPU itself - what exactly is the "front-side" bus? Is it the DRAM/memory-controller? Or is it the link from the CPU to the system chipset (HT link)? in terms of correctness, I would argue that it would be the HT link, since the "front" bus is the primary bus that the CPU communicates with the rest of the system with.

In that sense then,

[/i]"The FSB (or, for AMD processors, the HTT*), or Front Side Bus, is the channel through which your entire system communicates with your CPU. So, obviously, the faster your FSB can run, the faster your entire system can run." - Overclocking Guide[/i]

... is correct. Perhaps your concern is the possible implication that other busses derive their clock freqencies from a syncronous divisor of the FSB clock? That isn't true with many boards/chipsets anymore, and it isn't stated explicitly, so I don't see why that would be a problem either.

 

[VIAN]

I agree that the FSB is the connection between the CPU and all the other buses on the computer.

But I'm still correct that it doesn't speed up the system since the PCI bus still remains at 33MHz. Meaning the only thing you could do is speed up memory performance, which is the only other component besides the CPU that you can OC. This was my main point.

If you say otherwise, that means that if you weren't allowed to OC the RAM, there would be no other reason to raise the FSB. Unless you run out of multipliers, but then you would have an asyncronous RAM:FSB ratio which would suck. Would have to be tested.

 

[Appledrop]

vian... give up lol.

 

[miketheidiot]

Originally posted by: VIAN
I agree that the FSB is the connection between the CPU and all the other buses on the computer.

But I'm still correct that it doesn't speed up the system since the PCI bus still remains at 33MHz. Meaning the only thing you could do is speed up memory performance, which is the only other component besides the CPU that you can OC. This was my main point.

If you say otherwise, that means that if you weren't allowed to OC the RAM, there would be no other reason to raise the FSB. Unless you run out of multipliers, but then you would have an asyncronous RAM:FSB ratio which would suck. Would have to be tested.

If your motherboard does not have an agp/pci lock (most if not all are/can be locked now days) the pci/agp bus also OCed.

 

[Green Man]

Originally posted by: VIAN


The rest of the system runs on a PCI bus. This baby runs at 33Mhz which comes from dividing the FSB. Since modern mobos include a PCI lock so that when you increase the FSB, the PCI speed doesn't increase, because of stability issues, no matter how high your FSB is, you PCI bus, a.k.a. the rest of your system, will still run at the same speed.

Traditionally (read 440BX era) the northbridge and southbridge were linked by the PCI bus, but that is no longer the case. Even relatively older chipsets far exeed PCIs 133Mb/s throughput.
IIRC KT266 had 266Mb/s and KT400A had 533Mb/s. Even these speeds are eclipsed by NF3, a single chip solution that links to the CPU with HTT. Something like onboard sound would run on the PCI bus, but LAN, SATA, PATA even USB are removed from it.

PCI bus saturation was a real concern at one point, but it's no longer a problem.