Originally posted by: Soviet
I remember when these things came out, there was some discussion about AGP/PCI locks so you can overclock. I take it these come as standard on modern motherboards. Can i still overclock even if my mobo dosent have an AGP/PCI lock??
BTW what is this lock? Is it hardware or would a BIOS update probably get me it?
Yes you can over clock but it is adviseable that you increase the FSB frequency in increments of three and then test for stability, some motherboard manufacturers do release BIOS updates to lock these frequencies, but not all..
This is becasue the clock generator for the PCI BUS is 6 which equals 33Mhzx6 = 198Mhz, and the AGP clock generator is 3 which equals 66Mhz x 3 which = 198Mhz .. which is the speed of the system clock generator 198Mhz (acually 200mhz same diff
)
This means that for every 3Mhz jump in frequency for the the FSB, results in just a 1 mhz Overclock for the PCI BUS frequency and 0.5Mhz for the AGP (the PCI frequency is the most fragile BUS when it comes to Overclocks) this is because the Hard Drives run on the PCI Bus, and an highly OCed PCI bus will result in corrupt data over the FSB, which results in none boot of the OS, and major F-up's in the OS registery..
so going by that formula: for example 215Mhz FSB divided by 3 would = a 2.5/3Mhz increase in PCI frequency and 0.25/0.26Mhz on the AGP frequency, IIRC the average OC for the PCI BUS is 37Mhz ish YMMV, this is when data corruption comes in.. and average on AGP is around 75Mhz i think..
the clock generator for the system clock is always 1x this is becasue this is the main BUS in which everything communicates on, and everything else runs off of that for mulitplier division ..
EXAMPLE for you processor and other frequencies
System clock = 200mhz x1 - 200Mhz
Processor = 200mhz x10 - 2000Mhz (or 2Ghz)
FSB = 200mhz x2 - 400Mhz (or DDR400)
L2 Cache = 200mhz x10 - 2000Mhz (of course this is on die so it runs at the same clock as the proc)
AGP bus = 66mhz x3 =200Mhz - 66Mhz (always by default, also same clock as PCI-X for 64bit SCSI cards)
PCI Bus = 33Mhz x6 =200Mhz - 33Mhz (always by default)
notice that the PCI and AGP frequencies are not variable, this is why you need PCI and AGP locks because they are designed only to run at these speeds and nothing more .. so this is where locks come into play, they lock the frequency and allow you to mess around with the "system clock" clock generator as much as you want without affecting the PCI and AGP freqencies, and this also allows you to get more precise overclocks, as you will be able to raise the FSB/HTT in 1Mhz increments ..
so at the end of the day just get a mobo with PCI and AGP locks, as its much easier
RichUK
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