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7850 BE memory clock is not at 400mhz

Tags:
  • CPUs
  • Memory
Last response: in CPUs
July 7, 2009 4:25:03 AM

TLDR: Some Gigabyte Boards are not configured correctly from the manufacturer to achieve a 1:1 FSB to DRAM Ratio.

Reference Clock * Clock Multiplier = CPU Frequency
CPU Frequency / Memory Divisor = Memory Frequency

In my case this should be:

200 * 14 = 2800
2800 / 7 = 400

Which should support dual data rate DDR2 800 without a divider... however it displays as a 1:2 (FSB : DRAM) Divider.

What is going on?




SOLUTION:

After many hours of reading I found out the AM2+ Series of Processors handle the Memory Clock in a much different fashion than their AM2 counterparts.




Basically the Memory clock is listed in multipliers of the host clock, in this case I want a 400mhz memory clock to mate up with my DDR2 800 RAM, so I reduced the Memory Clock Multiplier from 4.00 to 2.00. This solved my issue.

-- HermanJr

More about : 7850 memory clock 400mhz

July 7, 2009 7:38:07 AM

Can you change the Memory Divisor? It's clear that it's half the clock multiplier, leading to your 1:2 ratio. Set the divisor to 14, so that you'll end up with memory frequency of 200.
July 7, 2009 7:52:23 AM

TonCharr28 said:
Can you change the Memory Divisor? It's clear that it's half the clock multiplier, leading to your 1:2 ratio. Set the divisor to 14, so that you'll end up with memory frequency of 200.



Thought I solved the issue, I was troubleshooting without following the #1 Rule of RTFM (Read the Freaking Manual) .. I didn't know AM2+ CPUs varied so much from their AM2 counterparts. Wrong Solution in Original Post.

Details Below.
July 8, 2009 12:18:30 AM

My orignal solution I tried last night did give me a 1:1 Ratio however to do so I lowered my DDR2 800 to DDR2 400, which gives a 1:1 Ratio but is crap for performance. The search it would appear is still on.