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Different FSB DRAM ratios shown in cpu-z and aida64

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June 25, 2011 4:18:47 PM

I have 16GB(4GB*4) 1600MHz GSkill Ripjaws memory on ASRock z68 pro3 mb, and the cpu is i7 2600K. The OS is win 7 64bit. Can you help me to clarify questions about the different FSB : DRAM ratios shown in CPU-z and aida64 cache&memory benchmark:
(1) what does FSB : DRAM ratio mean in Sandy bridge architecture?
(2) why do cpu-z and aida64 show different FSB : DRAM ratios? (1:6 in cpu-z, and 3:24 in aida64).
a c 347 } Memory
a b à CPUs
June 25, 2011 5:29:08 PM

1. FSB Ratio is the ratio between {FSB} a/k/a BCLK, Base Clock, etc and RAM speed.
2. Variations in you Base Clock. Normally it's 100 MHz but it can vary from 98±~104±.

Looking at your 1:6 it suggests your RAM running at 1200 MHz and (33.33) 3:24 (33.33 * 2) or 1600 MHz.

In my case on an X58 the BCLK is 133.33MHz and I get 2:12 on CPU-z or 66.66 * 2 : 66.66 * 12 or 133.33 : 800 MHz * 2 = 1600 MHz {DDR Double Data Rate}.

Look at your Memory tab and in CPU-z the DRAM Frequency should be 800 MHz or 1600 MHz. If it's not then run Prime 95 or some other app that's stressing the CPU and look again. If it's not 800 MHz then I can help set your DRAM Frequency, CAS Timings, DRAM Voltage.

Q - What RAM?

edit: it should be 1:8 OR 3*1:3*8 = 3:24 ; same ratio but 1:8 is the reduced ratio.
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June 26, 2011 12:28:04 AM

Thanks for your reply. The RAM is G.SKILL Ripjaws Series 8GB (2 x 4GB, 1600MHz) (URL). I bought 2 sets of 8GB successively, so now there is 16GB memory in total.

My CPU's BCLK is 100MHz, so what aida64 shows (3:24) matches the RAM's frequency (1600MHz). But cpu-z shows that DRAM frequency is 798.4MHz, but FSB:D RAM ratio is 1:6 which would give 600MHz DRAM frequncy. This is what I am confused about.


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a c 347 } Memory
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June 26, 2011 5:31:19 PM

Even if your Base Clock is 100 MHz and your RAM Frequency is set to 1600 MHz there are always some variations manly by the Base Clock and your reading of '798.4MHz' substiates the variation, the ratio per CPU-z is a rounding issue.

798.4MHz * 2 = 1596.8 / 16 = 99.8 MHz Base Clock.

If you'd like you could set the Base Clock to 101 MHz and see what CPU-z reads after the change. Never run the Base Clock above 105 MHz!

IMO - it's a mega-insignificant thing that I wouldn't think twice about :) 

edit: fixed spelling.
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June 26, 2011 5:40:47 PM

I mean, even considering the rounding issue, cpu-z gives contradictory DRAM frequencies. CPU-z shows (1) DRAM frequency is 798.4MHz, which is roughly 800MHz. (2) FSB:D RAM ratio is 1:6, which gives about 600 MHz DRAM frequency (since CPU BLCK is 100MHz, and I assume BLCK would not variate much). 800MHz and 600MHz don't match each other, even when taking into the rounding issue, right?
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a c 347 } Memory
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June 26, 2011 8:27:25 PM

I have not seen CPU-z 'code' The 'Ratios' are, I assume with variables that include Base Clock, DRAM Frequency, CPU/Type IMC, etc.

The DISPLAYED Ratios are from a Logic calculation; examples:

DISPLAYED Ratios
Case (
Base Clock ≥ 200 AND Base Clock/DRAM Frequency ≤ 0.25 ; "1:4"
...
Base Clock ≥ 133.3 AND Base Clock/DRAM Frequency ≤ 0.167 ; "1:12"
...
Base Clock ≥ 100 AND Base Clock/DRAM Frequency ≤ 0.125 ; "1:8"

etc... )

i7-2600, 100/800 = 0.125
i7-930, 133/800 = 0.167
AMD 955, 200/800 = 0.25

YOUR VALUE i7-2600, 100/798.4 = 0.12525

It's a CPU-z logic issue in it's coding, and somewhere in the coding your 1:6 came up and got displayed. Again, try Base Clock -> 101
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June 26, 2011 10:54:30 PM

Best answer selected by fashandge.
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June 26, 2011 11:02:19 PM

I tried BLCK 101MHz, the DRAM frequency shown in CPU-Z is 808.1MHz instead of 798.4MHz when BCLK is 100MHz, so the FSB : DRAM ratio is indeed 1:8, although cpu-z still shows that as 1:6. Thanks again, jaquith.
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a c 347 } Memory
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June 26, 2011 11:56:33 PM

I'll report it to CPU-z, it's gotta be an error in their coding. Apparently, this is an issue for others with the i7-2600K and perhaps other 100 MHz Base Clock SB CPU(s).

Here's a similar error, see @redduc900 comments -> http://www.overclockers.com/forums/showthread.php?t=671...

IMO - the only explanation is a overly complicated code AND/OR a improperly ordered ordered IF condition.
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January 27, 2012 1:07:09 PM

jaquith said:
I'll report it to CPU-z, it's gotta be an error in their coding. Apparently, this is an issue for others with the i7-2600K and perhaps other 100 MHz Base Clock SB CPU(s).

Here's a similar error, see @redduc900 comments -> http://www.overclockers.com/forums/showthread.php?t=671...

IMO - the only explanation is a overly complicated code AND/OR a improperly ordered ordered IF condition.



Hi. I don't get this. What is the FSB : DRAM ratio mean ?
How do I know what my base clock is ? Does it not mean my Front Side Bus frequency ?

For example I have a Wolfdale E6300 2.8 GHz and CPU-Z shows my 'bus speed' as 266.7 MHz and 'FSB' as 1066 MHz. And I have 2 GB DDR2 800 MHz RAM. Then in the memory tab the FSB:D RAM ratio is 2:3

What does this mean ? and what do timings mean and how do they work ?
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