Q6600: Sync vs Async and PCI Clock sync

I have been doing a lot of research on overclocking this processor, including reading graysky's guide and various posts, but I still had some questions. First here is my setup:

CPU- Intel Core 2 Quad Q6600 Kentsfield 2.4GHz
HSF- Thermaltake Frio
MOBO- ASUS P5K-V LGA 775 Intel G33 ATX Intel Motherboard
GPU- XFX Radeon HD 5850
Power Supply- XION Supernova XON-800R14N 800W ATX12V / EPS12V SLI Certified CrossFire Ready Modular Power Supply
HDD- Seagate Barracuda 7200.11 ST3500320AS 500GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive
Media Drive- ASUS Black 20X DVD+R 8X DVD+RW 8X DVD+R DL 20X DVD-R 6X DVD-RW 14X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2MB Cache SATA 20X DVD±R DVD Burner with LightScribe LightScribe Support
RAM- G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1000 (PC2 8000) Dual Channel Kit Desktop Memory
Case- Antec Nine Hundred

My first questions is about sync vs async. Currently, I have my memory set to DDR2-1000, which is the factory spec. For my first attempt I plan on following the guide and increasing the FSB to 333. Theoretically I could increase the FSB to 500 and still run in sync, correct? Of course I know this is probably impossible, so since I will start at FSB 333 should I be changing the divider or just leave it as is? Also, I can't seem to find anything in my bios for changing the divider.

Second, in graysky's guide it mentions a setting called PCI clock synchronization. I know the setting name may be different in my bios, but I can't find anything close to this, nor any other setting that allows me to adjust it to 33mhz as suggested. Any thoughts?


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More about q6600 sync async clock sync
  1. I just took a look at graysky's guide. Seems overly long and complicated because he tried to cover everything in one post instead of breaking things down into separate topics.

    I use primarily Gigabyte motherboards so, yet again, the BIOS is different. Second, even with one manufacturer's line, less expensive motherboards will not have all the settings that the more expensive models have.

    Memory clock dividers are one of those things that everybody handles differently.

    Here's my advice (yes, more guides):

    This should be your first stop.
    HOWTO: Overclock C2Q (Quads) and C2D (Duals) - Guide v1.6.1

    Next stop should be a guide for your particular motherboard. Google is your friend.

    Go through the guides. Then take your core voltage off Auto and set your memory voltage to factory recommended values. Change the System Memory Multiplier (or whatever your BIOS calls it - Asus uses "straps" for their Intel chipsets) from AUTO to 2.00, 2.00B, or 2.00D - whichever you need to set the Memory Frequency to twice the FSB. Then when you increase the FSB, the memory clock will rise in in proportion with it. At an FSB of 266 MHz, your memory clock should be at 533 MHz.

    Download CPU-Z to check your FSB:RAM ratio. It should be a 1:1 ratio.

    Warning - confusion factor between what the BIOS calls things and what CPUZ calls things. What the BIOS calls "memory frequency" is actually the memory clock. What CPUZ calls "memory frequency" is half the memory clock - DDR2 RAM, remember? It transfers two chunks of data each bus cycle. What you want in CPUZ is a 1:1 FSB:RAM ratio. With a 333 MHz FSB frequency, your RAM clock should be 667 MHz.

    Overclocking memory doesn't accomplish much - especially in a Core2 system - besides limiting your CPU overclock where the real speed comes from. Here's one place where we discuss that:

    You have another problem. The G33 is an "economy" chipset. That means two things. First, you are not going to have all the usual overclocking options (including the sync setting that you cannot find), hence the advice to look for a guide for your specific motherboard. And second, I doubt if you are going to be able to push the FSB frequency much past 333 MHz. That means that the capabilities of your DDR2-1000 memory are going to be largely wasted.

    Don't exceed 1.5 volts on the CPU cores and using CoreTemp or RealTemp, keep your core temps under 70 C.
    Overclocking since 1978 - Z80 (TRS-80) from 1.77 MHz to 2.01 MHz
  2. Thanks, JSC. Google is my friend! Found an overclocking guide with my exact CPU and MOBO. Also, the overclocking guide you linked is the same one I was talking about.

    Just to clarify: I should always set my FSB and memory frequency to a 1:1 ratio? There is nothing gained from running the FSB at 333mhz and the memory at 500mhz and this could possibly cause instability? Just want to make sure I understand correctly.

    I won't be able to give it a try this weekend, but Monday for sure. So keep an eye out, I may have more questions! ;)

    Thanks again,

  3. I am going to embark on my first over-clocking experiment.

    I have a Dell XPS 420 and two Inspiron 530s which have the Q6600. I know that the Dell BIOS disables over-clocking so I am going to use the pin-tape-mod.

    I noticed a few things:

    (1) On the XPS the CPU Core VID is 1.325V while the I530 has it at 1.152V.
    (2) According to SpeedFan core CPU Temperatures are lower on the XPS (low-mid 30s) compared to the I530 (mid-40s) even though the XPS runs on a higher voltage. I guess this what the better cooling of the XPS case gets you.
    (3) The XPS uses an X38 based Dell Motherboard while the I530 uses a P35/G33/G31 based MB (according to CPU-Z).
    (4) The original RAM sticks which came with the I530 are PC2-5300. According to CPU-Z these should be able to run at 333MHz at the same voltage (1.8V) as the 266MHz. I presume I will not have to do anything more.

    (a) Is there anything else I can do to speed up these systems?
    (b) Is it possible or recommended to reduce the voltage on the XPS system or should I not bother since it is running cool anyway?
    (c) Do I need to replace the cooling fan on the I530 if it continues to operate under 50C? Any recommendation on a reliable but inexpensive solution?
  4. An update to the above post. I have now done the pin mod on the I530. CPU-Z is showing Bus Speed at 332.5MHz, with Rated FSB a 1330.2MHz.

    I also noticed that there was a lot of gunk built up inside the case, and the heat sink was all dusted up. This perhaps was contributing to the higher temperatures.

    ->SpeedFan is showing temperatures of high 20s and low 30s now after I cleaned up the heat sink; I have set an alarm in SpeedFan and will monitor the computer to see if it truly needs a new heat-sink or the OEM Dell version will work fine.

    ->The base Core Voltage is now at 1.152V as before, but I have noticed that it occasionally climbs up (via CPU-Z). Perhaps there is some kind of automatic voltage scaling feature in these cores.

    -> The RAMs are running at 333MHz with 1:1 FSB:RAM ratio. 5-5-5-15, tRFC 44, CR 2T

    A happy camper so far; this is one of the simplest changes to do; it is completely reversible and if past history is any guide does not cause problems.
  5. An update to the update.

    Did the XPS 420 Q6600 tape mod. Things are working smoothly. Since I increased the frequency, I also enabled the advance SpeedStep from the BIOS.

    Now I am seeing lower voltages on the XPS also.

    I typically never open the PC box but the amount of gunk collected near the heatsink and the fans was a real eye-opener. The wind-flow path was almost completely blocked. Right now on low loads my cores are running at low 20s. During the day prior to the mod and cleanup, they reached mid-40s during the high load period.

    I wish I could do something to speed-up the RAM system on this board. It has the X38 based Dell MoBo. The sticks are running at 1:1 5,5,5,15 @ 333MHz.
    Added a few months later:
    For some reason the XPS420 became unstable after the tape mod. However two Insipron 530s wit the same Q6600 CPUs are working fine with the pin mod.
    I have changed the power supply to a 600W OCZ Modx Pro but that did not help. I suspect it has to do with the RAM. Will try switching that.
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