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Thread: OC Guide w/links

  1. #1
    Join Date
    Jun 2003



    please feel free to add or correct any incorrect or outdated info......


    The motherboard, CPU, memory, PSU and heatsink are probably the most important items when overclocking. Get the best products you can afford when selecting these. When reading ALTEC's and HITECHJB1's threads, you will understand why.
    ALTEC's very detailed guide to overclockingÖ
    Nerbil's ASUS A7N8X Overclocking Guide contains a lot of general info that applies to all mobos...

    BIOS Terms:

    ***credit to Nerbil for these definitions...some I tweaked to match fields found in the Gigabyte BIOS***

    All these settings are found in Advanced Chipset Features

    CPU Ratio Control: Commonly referred to as the "Multiplier," this number is multiplied by the FSB to equal the CPU Clock Speed. For example, A 133mhz FSB CPU with a multiplier of 15 runs at 1995mhz. (Multiplier * FSB = Clock Speed) "NORMAL" should be your default multiplier.

    FSB Frequency: Specifies the FSB frequency of the CPU. The FSB is doubled when referring to CPU - for example, 200FSB operates at 400fsb. Memory frequency is doubled also.

    Memory Frequency: This setting is the key to overclocking - this must be set at 100%. By doing so, the CPU and Memory are communicating in sync with each other, improving performance and stability.

    CPU Voltage Control: This controls the amount of voltage supplied to the CPU. In order for the processor to run at faster speeds, the vCore often needs to be increased. Here's a list of Stock Voltages, Multipliers and FSB's of AMD CPU's.

    Warning! Voltage = Heat! When adjusting the vCore, do it 1 increment at a time, and keep a close eye on your CPU Diode temps. Increased voltage will also shorten the life of any component - usually this means that instead of lasting 20 years, the chip might die in 5 - 10 years. Overclock at your own risk.

    Dimm Overvoltage Control: Similar to vCore, except this controls Memory voltage. When running the Memory FSB faster than specification, often times vDimm needs to be increased to give the memory an extra boost.
    adjusts in +1 and +2 (2.7 and 2.8)

    Memory Timing: These vary depending on your specific memory - always consult the manufacturer's website on the optimal settings. Often times, as the FSB goes up, these need to be "relaxed" by raising values. Here's a detailed Explaination of Memory Timings. You can start with an "OPTIMAL" setting, but if the timings need to be manually adjusted, set this to "EXPERT".

    AGP Overvoltage Control: This has very little impact to OCing - if experiencing Video problems, you can try raising this - but it usually makes no difference.

    AGP Frequency: Leave this at Auto or 66mhz.

    This is a very important feature to overclockers as running the PCI bus out of spec can cause HD data corruption and sometimes worse...

    ***credit to kim'grr @ overclockersonline***

    table of FSB / PCI / AGP clocks:

    FSB | PCI | Divisor | AGP | Another divisor
    100 | 33 | 3 | 66 | 1.5
    133 | 33 | 4 | 66 | 2
    166 | 33 | 5 | 66 | 2.5

    When passing the FSB clock where you've got a divisor which will give you a normal 33mhz pci bus, the specific divisor will stay activated until you reach the next FSB / X = 33mhz "point". Let's say you go from 133 to 146mhz, your fsb / pci divisor will be 4. So your pci clock will be 146/4 = 36.5mhz.

    On some boards does the "next" divisor kick in a bit earlies than expected, like at 124mhz suddenly you'll have the divisor of 4.
    The AGP "problem" works the same way as described above, just with a diff. divisor and it affects your gfx-card.


    AMD CPUís
    lots of info on AMD CPUís/Overclocking
    AMD CPU descriptions/IDís
    find out about your CPU (input stepping code)
    HITECHJB1's detailed analysis/review of a 1700+ overclock..with lots of extra info.

    wire/paint mods for cpu's
    L12 bridge mod
    John's Homepage that exlains workarounds, mods...


    Heatsink Performance ratings


    Memory Timing Definitions:

    ***again, thanks to Nerbil for these.***

    Decoding Memory Timings: Example Corsair XMS2700 @ 2-3-3-6-1T
    CAS Latency: 2
    RAS Precharge (tRP): 3
    RAS-to-CAS Delay (tRCD): 3
    Bank cycle time (or tRAS): 6
    Command Rate: 1T

    CAS latency is basically the number of clock cycles (or Ticks, denoted with T) between the receipt of a "read" command and when the ram chip actually starts reading. Obviously, lower numbers will result in less of a delay when memory is being read from. Corsair's website claims a low single digit % gain from CAS-3 to CAS-2. Memory can be basically visualized as a table of cell locations, and the CAS delay is invoked every time the column changes (which is far more often than the row changing). The differences in memory bandwidth concerning CAS latency were non-existent (and it is just as likely that any recorded performance gains are attributed to random events, as performance gains were not at all consistent). There was no significant gain in memory bandwidth from adjusting CAS latencies.

    Precharge to Active (tRP):
    The Precharge to Active timing controls the length of the delay between the precharge and activation commands. This influences row activation time which is taken into account when memory has hit the last column in a specific row, or when an entirely different memory location is requested. The gain from optimizing the tRP value (3T to 2T) seemed to scale with higher FSBs (10MB/sec at 100 FSB, 20MB/sec at 166 FSB), giving a consistent .1% increase in performance. I highly doubt that this .1% in memory bandwidth would translate to a noticeable (or significant) real world increase.

    Active to CMD (Trcd):
    This timing controls the length of the delay between when a memory bank is activated to when a read/write command is sent to that bank. This basically comes into play when the memory locations are not accessed in a linear fashion (because in a linear fashion, the current bank is already activated). This option gave a consistent 20-30 MB/sec gain in memory bandwidth (3T to 2T), with the results pointing to a slight scaling at lower CAS latencies and higher FSBs.

    Active to Precharge (tRAS):
    The Active to Precharge timing controls the length of the delay between the activation and precharge commands -- basically how long after activation can the access cycle be started again. This influences row activation time which is taken into account when memory has hit the last column in a specific row, or when an entirely different memory location is requested. As with CAS, the performance gain (7T to 6T) was inconsistent, and possibly could be attributed to random variables.

    DRAM Command Rate (self-abbreviated DRC):
    I'm going to take a quote from Adrian's Rojak Pot in order to explain this setting: "This BIOS feature controls how long the memory controller latches on and asserts the command bus. The lower the value, the faster the the memory controller can send commands out." A faster DRAM Command Rate (3T to 2T) results in a consistent 30MB/sec gain in memory bandwidth.

    Prime 95
    [email protected]
    [email protected]
    memtest 86
    CPU Burn
    Sisoft Sandra
    Benchmark page @ Major Geeks

    Motherboard Monitor 5
    CPU-Z...i think this is slightly better than CPUID.



    Stitch's FAQ addresses this for G-byte boards.


    PR3ACH3R has put out some modified BIOSís for the GA-7N400-L1 and GA-7N400PRO that make other features available that were disabled by G-byte or fixed bugs that were in the factory BIOS. These are very good BIOSís as I have seen many use them w/out problems. Keep in mind that there are no guarantees when using 3rd party BIOSís.


    The standard means of accessing the BIOS applies here as well. In order to get "advanced" BIOS settings, hit "CTRL-F1" while in the main menu. you may notice a slight blink/flash of the screen. Once this is done, you can access options not available when going directly in to the BIOS.


    this is a windows based overclocking and monitoring utility that eliminates the need for BIOS setting changes. the monitoring feature seems to work pretty well as it matches what the BIOS reads. overclocking adjustments are easy enough to make but i still prefer to use the BIOS.


    Taken from the G-byte website: "the Dual Power System delivers a total of 6-phase power circuit design to provide more solid and durable power supply for the new generation AMD platform."

    I've read of many people having problems with this feature and they wind up not using it. A good, quality PSU should be enough....


    If you cannot get your system to post after messing around in your BIOS, you can hold down the "insert" key while rebooting/powering up...this seems to work with all nF2 mobos...
    Stitch's G-byte 7NNXP FAQ.
    Gigabyte Homepage
    Barton 2500+ (218x11) - SLK800A w/Vantec Tornado - G-byte GA7N400L1 - 256x2 TwinMOS DDR400 - BBA R9600Pro - Antec 350W

  2. #2
    Join Date
    Sep 2003


    the links are great...need some illustrations, tho.

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