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I7-920 multiplier is changing from 21 to 20 under prime95 load

Last response: in CPUs
January 14, 2012 7:04:32 AM

I have the multiplier set to 21x in the bios. Sitting here right now I look over to cpu-z and see 4022mhz and a 21x multiplier. As soon as I start prime95 testing the multiplier drops to 20 and i only get 3850mhz. Whats the deal?
a c 184 à CPUs
January 14, 2012 7:05:02 AM

You have turbo boost or speedstep enabled.
January 14, 2012 7:10:41 AM

I have Intel EIST disabled in the bios which is the speedstep technology.
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January 14, 2012 7:16:24 AM

Any other ideas?
January 15, 2012 4:37:15 AM

I've tried everything I can think of. Help :p 
a c 90 à CPUs
January 15, 2012 6:57:59 AM

you can only use the 21 multi if you have turbo turned on, prime 95 disables turbo so you will be dropped to the 20 multi...
note you can set the 21 multi in bios but if you also disable turbo. the 21 will still be show, but you will be running on the 20x multi
January 15, 2012 10:33:28 AM

Thanks for the info. Is there a program out there like prime95 that will support the x21 so I can load test my setup?
a c 90 à CPUs
January 15, 2012 9:21:06 PM

you are already getting the max load out of it m8, the reason its not allowing turbo is because turbo makes 1 core perform higher than the rest. but there must be an even timing across all cores for the stability test to be representative of the cpu as a whole. turbo mode will add instability and is not recommended to be on with an over clock as it may cause uneven temps leading to a cpu fail if 1 goes over the max tdp

all benchmarks will (or are supposed to) level out the timings. another that i know does it is future marks 3dmark... across all versions it ignores any turbo settings. because they are not representative of all the cores.
January 16, 2012 10:14:35 AM

So how is it that I see so many people posting up at 21x multiplier? Am I missing something?
a c 90 à CPUs
January 16, 2012 11:34:20 AM

coz there leavint turbo on but ar clocking higher 2? i dunno... im just going of what my cpu does.