Overclocking question

[akaneria]

hi,
i have a asus P5B MB with a e6600 2.4 ghz
it has the artic freezer cooler and artic silver 5 paste

I have put the FSB up from 266 to 290 and left the DRAM on Auto.
This has brought the speed up to 2.610ghz whcih is stable with prime95, however it was getting a bit hot, so i decided to drop the vcore (was also on auto) to the lowest possible option amount available, whcih ran stable and much cooler, 35-36c.

When i tried to increase the fsb to 300 the computer just wouldnt boot up, so i had to manually clear the CMOS, does anybody think its to do with the vcore being too low as the reason for not booting up.
I want to keep the processor as cool as possible but as low voltage as possible.

I dont really want to keep clearing the cmos to find the correct voltage

[Thorsson]

It may well be the VCore.

It may also be your RAM. Firstly you need to check what voltage it's getting and compare that to specs. Some RAM is specced for higher voltage than Auto will give. Secondly Auto also ups the RAM speeds on some motherboards: check what ratio yours is running at, and put to 1:1 if 300 takes it past its speed.

If these settings are OK then try upping VCore a notch at a time until it's stable running prime.

[akaneria]

the ram is 2gb corsair xms2 6400 800mhz
i have left this to auto, what should be the best option, 533, 666 or 800?
On my MB is doesnt give an option for ratio.

[Noxvayl]

Put it on 533... you want your RAM on the lowest option so your RAM doesn't become the bottleneck for the overclock. After you get further with the overclock its more than likely that the RAM will get to its rated speed anyway. If it doesn't you can go into the BIOS and put it up a level to see if it will run anyway.

As for the voltage leave it at its recommended level(which I think is 1.3v) and continue to put the speed up. Auto was most probably over volting the CPU because of the overclock causing the higher temps. When your PC gets unstable with the overclock the further you get up the voltage ever so slightly to help stabilise the system. Also 40C at idle with your cooler is not unusual when overclocking, its when it passes that at idle you need to hold back because then load temps would be a bit high for anyone's liking.

I don't think you'll be able to reduce the voltage while overclocking and I am pretty sure that is what caused the boot problem.

[akaneria]

cheers mate for the info,
its really helped as i am a total beginner at this.
Just another question, if you fix the rambus at 533 and still overclock will it still up tthe speed on the ram, or will it only do that if its on auto?

also on the vcore side of things, if i fix it to say 1.25v will that be ok?

the 40-41 idel at 2.6ghz is with the fan on Qfan on silent.

[Noxvayl]

Yes the RAM speed will still increase.

Lower voltage does mean less heat but it also means less stability because the chip requires a certain amount of power in order to function properly. 1.25v should be ok to work as far as you have overclocked at the moment(most C2D chips I've encountered are fine with that voltage at your stage but its all dependant on your chip). Each CPU is different so sometimes you can go pretty far without needing to up the voltage other times you need to up the voltage for small overclocks. Basically in order to remain stable we up the voltage of the CPU as long as we have the cooling ability to handle it. So you need to strike a balance between heat created and overclock because if you go too far you could cause damage to the CPU. What you want to do is remain within 60-65C under load temps(running prime95 or orthos to stress the CPU). 60-65C is relatively safe, its not a comfortable temperature but its within Intel guidelines which means it shouldn't be damaging to your CPU.

Overclocking in simple terms is increasing the core clock speed in order to increase the speed of components which use it to derive there individual frequencies.

More in depth explanation: Your PC uses a core frequency to synchronise its actions so that when one component sends information to another component the component receiving it is at the cycle stage to be ready for receiving the info. This stops information being held up in the bus waiting for the specific component which improves efficiency. To do this synchronisation the system needs to be run on one single core frequency and the other components then use multipliers to get to there individual frequencies. So when we go into the BIOS and increase the speed we are changing that core frequency which then in turn increases every thing's frequency that uses the motherboards core clock speed. The only component not using the motherboards clock speed is the GFX card which has its own independent core clock(its essentially a motherboard with GPU embedded) so other than that all other components with a rated speed basically multiply the motherboards clock speed to get there's.

You seemed like someone who likes to be more informed so I went more in depth. Hope it helps and answers your questions. Happy to answer any more you might have

[akaneria]

Thanks for the in depth info ExHail, really appreciate it!

Also i just upped the FSB to 300 so the it takes it to 2.7ghz, however i fixed the rambus at 533, but when i open up cpuz
under memory it shows the DRAM frequency at 299.9mhz not 800mhz as my ddr2 6400 should be?
and the FSB : DRAM ratio is 1:1

is this alright?

[shaffaaf27]

yes thats fine.

if you want to run the RAM it its full rated speed, just increace the ratio of FBS:RAM frequency

[Noxvayl]

When you set the RAM to 533 you lowered its multiplier so its speed would decrease. As you go further with the overclock the speed will slowly rise. Once you have found the limit of your processor and motherboard then you can set the memory higher until it comes close to its rated frequency.

The reason you set the memory up like this is because the memory is the least overclockable component that uses the core frequency so you don't want the computer to stop booting because of the memory when the motherboard and CPU can potentially go much further in an overclock.

[akaneria]

cheers for the info, but i still don't quite understand the relationship between the FSB and the RAM Bus.

If i left my cpu on auto at stock speeds FSB 266 2.4 GHZ would the ram ever reach the speed rated on the sticker of 800mhz (DDR 6400)? I always thought that if i bought ram dd2 6400 it would run always at 800mhz. pretty confused

If i have set the rambus on the bios at 533 then why does it show on cpuz as 299.99?

http://img240.imageshack.us/my.php?image=cpuzzy5.jpg

http://img123.imageshack.us/my.php?image=cpuz2xj6.jpg

[Thorsson]

It's Double Data RAM, which means that's 600 (near as damnit). That would indicate an FSB of 300. You should have a multiplier setting in the BIOS which will bring the RAM speed back up when you have an FSB clock you're happy with.

[akaneria]

i dont seem to have any multiplyer setting in my bios, its an ASUS P5B

[Noxvayl]

Some motherboards have ratio settings like 1:1 or 1:1.25, other motherboards have number settings like 533 and 667 and other motherboards use number letter combinations like 2.0a or 2.66a to distinguish between different default core clock("a" refers to which default core clock is used and the number 2.0 refers to the multiplier associated with it. They are all different representations of the exact same ratio system applied to every motherboard. Here is a different type of explanation of the ratio's with regards to your specific boards representations of them:

RAM works on a ratio related to the core clock. DDR2 means Double Data Rate 2 which refers to the data being transferred in both directions at the same time instead of only one way(like a one way road as opposed to a road with traffic flowing in both directions) and the 2 at the end refers to the multiplier automatically used for all DDR2 RAM chips because they can operate at higher frequencies because of architecture enhancements over plain DDR, DDR3 uses 3 as a multiplier because of its enhancements over DDR2. So your normal core clock is 266Mhz so we will take that as the base. From there for every RAM related calculation you multiply it by 2 because of the DDR2 explained above. Setting the RAM at 533 means that the RAM uses a ratio of 1:1 which if the core clock is 266 then the RAM would run at 533Mhz, 266X2X1(1 being the ratio multiplier used for the 533 setting and 2 being the DDR2 multiplier used for all DDR2 RAM). If you set the RAM as 667 then its ratio would be 1:1.25 which would make the RAM speed 667Mhz, 266X2X1.25, and finally if you set the RAM at 800 its ratio would be 1:1.5 which would make it run as 800Mhz, 266X2X1.5. All shown calculations are very slightly off because the actual default core clock(for your motherboard and CPU combination) is 266.5 which will give you the proper rated frequencies.

So when you overclock you increase the core clock speed and at the same time the memory speed rises. So if you had the core speed at 300Mhz instead of 266Mhz and set the RAM to 800 in the BIOS the resulting speed would be 900Mhz(300X2X1.5) the multiplier always remains the same for each setting on the motherboard. Now normally on average RAM chips rated at 800Mhz they don't like to go much further than 900Mhz(there are some which are specifically designed to overclock well and can easily go above 1000Mhz but that's not the normal set they are more expensive). So to stop the RAM from keeping your overclock down you set the RAM at 533 or 667 which would be 600Mhz(300X2X1) and 750Mhz(300X2X1.25) effective frequency. This means that the memory is still below its rated speed so you can easily go further with the overclock should your processor and motherboard be able to.

So from this you can easily project what the frequencies of your components will be from what you set the core clock to. Examples with 533(1:1 ratio) RAM setting and Q6600(9 multiplier):

266Mhz(actual default clock is 266.5, don't think they want to show the decimals so just automatically round it down in the BIOS) core clock = CPU - 2394Mhz(2.4Ghz from 266.5 core clock), FSB - 1064Mhz(1066Mhz from 266.5 core clock) and RAM - 532Mhz(533Mhz from 266.5 core clock),

300Mhz core clock = CPU - 2.7Ghz, FSB - 1200Mhz, RAM - 600Mhz

350Mhz core clock = CPU - 3150Mhz, FSB - 1400Mhz, RAM - 700Mhz

400Mhz core clock = CPU - 3600Mhz, FSB - 1600Mhz, RAM - 800Mhz

Now this doesn't mean that that is how far you can go with your overclock but it is a projection of what your actual speeds will be when you reach those specific points. The calculations shown are basically an explanation for how the motherboard(FSB), CPU and RAM use the core clock frequency located on the motherboard.

[akaneria]

I have just read your post, its incredibly easy to follow, and now at last i totally understand the relationship

Thankyou very much Exhail, i will certinly save this, espically paragraph 2 for my records.

Very much appreciate this

[Noxvayl]

I have just read your post, its incredibly easy to follow, and now at last i totally understand the relationship

Thankyou very much Exhail, i will certinly save this, espically paragraph 2 for my records.

Very much appreciate this

No problem m8. It took a few more paragraphs then that to get me to grasp the idea the first time But once you start to understand it sticks with you. Its always nice to understand how things work, well I enjoy finding out how things work

[shaffaaf27]

DDR3 doesnt use a 3 times multi over DDR2, its that it is Quad pumped FBS, just like Intel CPUs.

the data is transmited twice on the falling and rising side of the RAM (usually when paging /and the High Level scheduler taking and giving instruction to and from the CPU)