Need help with overclocking basics

[iOL]

Hi members,

I need some help to understand the basics of overclocking. I dont really know where to start, i'll try to be has clear as possible.
On some post David asks:

Should the DDR2 memory DRAM Frequency be as close to the Bus Speed of the CPU as possible?

David specs:

DRAM Frequency - 301.1 MHz
FSB : RAM - 2:3
CL, tRCD, tRP - all 4 clocks
Cycle Time - 12 clocks
Core Speed 3010.8 MHz
Multiplier - x15.0
Bus Speed - 200.7 MHz
FSB - 802.9

Then paul explain that we should consider the real transfer rate in mb/s of both the memory and the processor bandwidth to match.

Paul calculs:

if you had dual channel memory at PC2-4800 (which is DDR2-600 rate),
the bandwidth might look like 2*4800 = 9600MB/sec
The processor is 8 * FSB800 = 6400MB/sec.

The first calcul is 4800 * 2 because its in dual channel thats ok.. But on the processor one (8 * FSB800) where does the 8 come from?

I also have some other question about this after someone kindly help me get this clear.

 

[iOL]

With google, i have some progress:

8 counts as the amount of "bits" per data cycle.

Before i can understand this, there comes another question: How can i know how many transfers per Clock Cycle my cpu can do?

Number of cores 2 (max 2)
Number of threads 2 (max 2)
Name AMD Athlon 64 X2 5200+
Codename Windsor
Specification AMD Athlon(tm) 64 X2 Dual Core Processor 5200+
Package Socket AM2 (940)
CPUID F.3.2
Extended CPUID F.43
Brand ID 4
Core Stepping JH-F2
Technology 90 nm
Core Speed 2612.2 MHz
Multiplier x FSB 13.0 x 200.9 MHz
HT Link speed 1004.7 MHz
Stock frequency 2600 MHz
Instructions sets MMX (+), 3DNow! (+), SSE, SSE2, SSE3, x86-64, AMD-V
L1 Data cache 2 x 64 KBytes, 2-way set associative, 64-byte line size
L1 Instruction cache 2 x 64 KBytes, 2-way set associative, 64-byte line size
L2 cache 2 x 1024 KBytes, 16-way set associative, 64-byte line size
FID/VID Control yes
Max FID 13.0x
Max VID 1.350 V

 

[Wishmaster]

Perhaps Im confused but, what exactly are we talking about here?

AMD or Intel? And what generation/what chipset etc.

Each configuration will be a bit different.

 

[iOL]

Im not talking about a specific manufacturer but in general. As i said i try to as clear as possible.

Also, i'v found something about the "transfers per clock cycle"

Let's say a cpu operates at 8MHz. That means it breaks down time into little units per second. The number of units per second in this case is 8 million (1 MHz = 1 million Hz). The CPU sees "time" as being 8 million units per second, with each unit being a clock cycle.

The amount of data that can be sent by a bus per clock cycle is the bus width - If a bus width is 16-bit. On each clock cycle, 16 bits of data are sent, or received, depending.

So if i understand correctly, this cpu would transfert (8 000 000 * 16) 128 000 000 bits in a second?

128000000 bits = 16000000 byte = 15.25 mb/s

That doesnt make any sense 15.25 mb/s is way too much for a 8 mhz cpu !?

 

[iOL]

I see what im missing:

Assume that this microprocessor has a bus cycle whose minimum duration equals four input clock cycles.

The info we really need is the external bus width (16-bit), the CPU clock speed (8MHz), and the fact that the external bus clock cycle is 1/4 the speed of the CPU.
So the bandwidth of the external bus (often called the FSB or Front-Side Bus in today's CPU's) is the width times the speed. The width is 16-bit, the speed is 1/4 of 8MHz = 2MHz

Here is the complete thread

It takes a minimum of 4 internal bus clock cycle to do a "transfer"
The internal bus clock cycle beeing 8 mhz in this case (8 million units per second)

Am i right?

 

[Lordbob75]

That thread has nothing to do with overclocking, it's about data transfer speed of CPUs.

Overclocking is increasing the speed of the processor, and you don't need to know that much detail to do it.
The general idea is that you increase the clock speed and/or core clock of the processor until it is as fast as you want it or it can go. The actual method is a bit different depending on the CPU though.

~Lordbob

 

[A Guy]

That thread has nothing to do with overclocking, it's about data transfer speed of CPUs.

Overclocking is increasing the speed of the processor, and you don't need to know that much detail to do it.
The general idea is that you increase the clock speed and/or core clock of the processor until it is as fast as you want it or it can go. The actual method is a bit different depending on the CPU though.

~Lordbob

Agreed. If you were seeking edification on the information in that thread, that is different. But if you were seeking it in regard to overclocking, it isn't needed. A Guy

 

[Corpsecrank]

The basics of overclocking is simple get a motherboard and chip that allow it first. You want a board that has all the bios options open to manually control your cpu settings and a cpu that is not locked. For AMD the black edition processors are the unlocked ones that can be overclocked for intel I have no idea which are unlocked and which are not. Buy a good overclocking motherboard though one that is specifically for overclocking or that you know has a lot of options.

The rest is trial and error really. Go into the bios and start manually adjusting setting a little bit at a time. DO NOT crank the voltage though. That is the one thing that WILL kill your processor. You can adjust the clock speed all you want hell crank it to 7 or 8ghz the worst case there is that it won't boot up and if it does it will surely crash out shortly after probably before windows fully loads up.

But you want to start small only a couple hundred mhz. If that runs good for a day or so you can bump it another 100mhz until you start to see issues with your system. General weirdness like glitchy graphics in games or things freezing up randomly. If you get very minor glitchyness you can try adjusting the voltage at that point. Slight and I mean the smallest increment offered on voltage at a time.

Bump the voltage one small notch and run the system. If things are still not stable bump it once or twice more. Make sure not to go very far with voltage. If bumping the voltage a couple of notches does not solve the stability issues take the clock speed down a notch and back the voltage down again.

Once you have more experience with this you will be able to do more but that is a good starting point.

 

[iOL]

Thank's guys for your answers i appreciate. I guess the title should have been "Need help with computer architecture basics". I guess i had in mind to overclock my old pc while really knowing what i was doiing. So i had to understand a few things.

Is it too late to keep goiing with the "Data Transfers per Clock Cycle"?

Not all processors will use a "Four Data Transfers per Clock Cycle" system. The old Athlon XP only used a dual (2) system.

Where is it possible to find this info about any cpu?

 

[Lordbob75]

Not all processors will use a "Four Data Transfers per Clock Cycle" system. The old Athlon XP only used a dual (2) system.

Where is it possible to find this info about any cpu?

I would think that the CPU information and spec page on the companies website would have the information, but I have never actually looked for it. Not sure what it would be listed as either.

~Lordbob

 

[iOL]

Not sure what it would be listed as either.

So we can find the bandwidth that the cpu can deliver?

theoretical bandwidth of the external bus = external bus width * (cpu frequency / Data Transfers per Clock Cycle)

I would have liked to know this info about my cpu