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How does the BIOS Memclock to CPU Ratio Limiter work? My system is unstable.

post #1 of 6
Thread Starter 
I'm overclocking my FSB and using the BIOS Memclock to CPU Ratio Limiter.

The selections look exactly like this:
1:1 (DDR 200)
4:3 (DDR 266)
3:2
5:3 (DDR 333)
2:1 (DDR 400)

When I set the FSB to 231 and the divider to 5:3, CPU-Z reports my DRAM frequency to be 198MHz. Shouldn't I be getting 192.5MHz?

When I set my FSB to 241 and the divider to 3:2, CPU-Z reports my DRAM frequency to be 198MHz. Shouldn't I be getting 180.75MHz? Setting the FSB to 240, CPU-Z reports the DRAM frequency to be 197.2MHz. That is slightly below the 198MHz, which makes sense.

When I set my FSB to 250 and the divider to 3:2, CPU-Z reports my DRAM frequency to be 196.4MHz. Shouldn't I be getting 187.5MHz? This is really strange because I increased my FSB and left the divider at 3:2, and it resulted in a lower DRAM frequency. Does changing the CPU Multiplier explain this?

I ran Windows XP 32-bit with a 243MHz FSB and 3:2 limiter for three years without any problems. Now I upgraded my CPU and set the FSB to 241MHz and the limiter to 3:2 and my system has frozen when using foobar2000, Chrome and Youtube, Control Panel and Windows Update, StarCraft 2, and just idling at the Start Screen or using File Explorer.

I've ruled out bad memory with a 12 hour memtest86 run (with the FSB set to 200 and limiter to 2:1). I've ruled out CPU instability with a 27.5 hour prime95 run. I've ruled out heat. It's frozen after trying the following troubleshooting measures: Increased PCI latency delay, increased video card voltage, disabled video card control services and startup items and disabled video card overclocking, disabled audio device startup item, removed PCI audio device and switched to onboard audio device and disabled it's startup item, disabled sleep mode, switched from video card manufacturer driver to basic Windows video card driver, increased RAM TRP to 3, increased RAM CL to 2.5, unplugged all peripherals except mouse, keyboard, monitor, ethernet and 1/8" stereo jack, increased hypertransport from 3x to 4x, and disabled Windows Update.

I suspect either the BIOS Memclock to CPU Ratio Limiter, the 1/8" stereo jack connection with my new speakers, Windows 8 itself, an undiscovered hardware short or the 2MHz underclock on the memory to be the causes. Right now I'm trying to get the DRAM frequency closer to 200MHz, but I'm running into the heat limit by pushing the voltage up high enough to get the FSB there, and I have to go a long way down to use a higher Memclock to CPU Ratio.

What's the deal with the DRAM frequencies I'm getting? And do you think that a 2MHz underclock on the RAM explains the freezing? Should I try loosening some timings next, and if so, which ones?

Thanks very much for your help.
Edited by Caribou007 - 7/7/13 at 7:19pm
post #2 of 6
Thread Starter 
bump
post #3 of 6
What CPU / Mobo do you even have?

The memory clock depends on the Base clock, and the base clock might fluctuate a little under windows, and that is why your mem speeds are a bit faster in CPUz.
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Power Bac G5
(8 items)
 
  
CPUGraphicsRAMHard Drive
i5 6600K @ 4.5Ghz R9 280X with no FreeSync support 8GB 2800Mhz Samsung 850 EVO 250GB 
Hard DriveMonitorPowerCase
2x ADATA SP550 120GB RAID 0 AOC 4k FreeSync TN Panel EVGA SuperNova NEX 750B Parts Directly On Top Cardboard Box 
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post #4 of 6
Thread Starter 
What effect exactly does Windows have? How does it make the DRAM frequency up to 20MHz lower than it should be. Why does increasing the FSB sometimes lower the DRAM frequency?
post #5 of 6
Thread Starter 
Could the V-Link voltage be causing this freezing? I never changed it from it's default of 2.5V. I could set it to 2.6V.

Do you want to see the CPU-Z screenshots of Standard CPU Frequency/Voltage and Auto Memory Configuration or the settings that had passed my tests but are still freezing my system?

Note that even when all settings are left at the Setup Defaults except for the CPU Frequency/Voltage overclock, the system still freezes. So apparently the CPU Frequency/Voltage overclock is what is making the system unstable, not the Memory Configuration or anything else.
post #6 of 6
Thread Starter 
Quote:
Originally Posted by TheLAWNOOB View Post

What CPU / Mobo do you even have?

The memory clock depends on the Base clock, and the base clock might fluctuate a little under windows, and that is why your mem speeds are a bit faster in CPUz.

What effect exactly does Windows have? How does it make the DRAM frequency up to 20MHz lower than it should be. Why does increasing the FSB sometimes lower the DRAM frequency?
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