fsb:dram ratio in newer processors

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metalspider

Weaksauce
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Jul 13, 2006
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ive been trying to understand this subject as im trying to overclock my pentium d 930,however
i dont quite get it.at stock speeds my ratio is automatically 1:2 does this mean the ram is running twice as fast as cpu or half as fast?
1:1 is the goal but i tryed running my ram at half speed and cpuz wont show me the ratio on my gigabyte ga-965p-ds3 board at this setting.

can you help me out?all the guides i found on google were for older cpus and lower speed rams and i think things have changed since then,im i wrong? thanks.

btw i have 2 1gb dimms of ddr2 800 corsair ram (5-5-5-12 according to corsair but pcuz says spd is 5-5-5-18 which im also unsure about)thanks.
 
I'm in the same boat as you... when i over clocked my CPU, my memory went all haywire... it was 1:2 but the clocks were very high, like in the 30s. i ended up restoring the default settings and trying again. i believe i left everything on auto except for the trc, which i set to 8. for a 4.0-4-4-8 timing. my ratio has jumped to 9:16 also.

im trying to find an answer on whether or not raising the FSB will bring that ratio down and keep my timing at 4-4-4-8 before trying to implement it... the last time i dove into OCing the memory, my system shut down and wouldnt start up again.
 
Read the overclocking guide sticked near the top of this forum, it should answer your questsions.
 
someone tell me if i got this right.
amd processors up untill recently would work best a 1:1 even if ram could run faster,intel is able to work better at some cases in a non syncronus ratio because the memory controler can utilize the higher the extra bandwidth the ram gives when its running faster than the fsb.
nowadays lowest ratio on intel is 1:1 and everything else has ram running faster than cpu fsb.

becuase of dual channel ram controllers the highest ratio is 1:2 which means ram is effectively twice as fast as fsb.

so to overclock just find fastest fsb and get ram to work as fast as it can.(to keep it easy say at the rams factory rating or slightly higher with same timings)

did i get it right?

thanks
 
it depends on what you mean by recently. K8 never has run the memory "1:1" in a true sense, so basically ever since a64s came out, the logic of "1:1 is better" got thrown out the window. memory controller runs at cpu clock, so there's usually a divider that looks something like cpu/11 setting the memory clock

for intel, memory controller is either set by or runs off the FSB clock (still not 100% on this :() however, the fact that it's dual channel memory has NOTHING to do with the actual memory speed ;)


but other than that, yeah, you got it right. keep the memory ratio at 1:1 initially, find the max speed the cpu can do, then bring the ram speed up as high as you can by raising the ratio, and bench along the way to find the optimal trade-off between memory clock, timings and ratio
 
ok thanks.
one question though,since ram is always at atleast 1:1 or faster than fsb how come some ratios fail and i cant even pass the POST test even if at said ratio my ram is set to run well within (or in somecases under) its rated speed?
 
yea, he said something about a 5:4 ratio and the memory runing at 80% of the FSB, but ive never been able to get a ratio like that... would i have to under clock my memory? what seting would i play with? the timings, voltage, or FSB?

right now im at a 1:1.6 ratio running OCZ gold at 4-4-4-8 but getting 4-4-4-15-19 or something close to that. ill keep re-reading till i figure it out.
 
metalspider said:
ok thanks.
one question though,since ram is always at atleast 1:1 or faster than fsb how come some ratios fail and i cant even pass the POST test even if at said ratio my ram is set to run well within (or in somecases under) its rated speed?
Click to expand...
what ratios and fsb speeds? you have the memory timings manually set?
 
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