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- Nov 30, 2012
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Hi guys, just to share, I think I found the problem with 4 dimm memory instability on haswell gigabyte (Z87/H87)
I collect a lot of information about memory changes from z68/z77 to z87 and found that memory subtimings has changed, and now we have "haswell compatible memory" for some brands. I didnt find all changes but it clear to me that tRFC and tFAW have higher values now.
and comparing some memory brands who has 16GB (2 sticks) and 32GB (4 sticks) on the same model/IC, I also found tRFC and tFAW higher on the 4 sticks kit.
so, first conclusion is: HASWELL NEEDS HIGHER tRFC and tFAW and 4 DIMM needs even HIGHER values.
I dont know how other motherboard brands solve this, but gigabyte still isnt fix the 4 dimm problem on their boards, you can see a few users happy using brand new memories from QVL (gigabyte have a very small ones) but there is a lot of people still getting problems.
I have a old 16GB 4 DIMM memory kit with works fine at 2 DIMM XMP 1600Mhz 1.35v at my H87 board, but wont work at all with 4 DIMM. i try everything: lowering timing/latency, increase System Agent,, IO Digital/Analog voltage and several others tricks without success. But I didnt try on sub-timings values and when I see the values I notice that are VERY LOW tRFC and tFAW compating to other 4 DIMM kit. it seems tRRD is also related to tFAW, so i recommend higher a little (I use 8)
so, if you can try a little experiment with 4 dimm, do this:
1) note (or print/photo) all RAM TIMINGS you are using on XMP profile.
2) disable XMP profile and put memory timing on MANUAL
3) change manually all timings values to the XMP values you printed, but increase tRFC to 280˜310 and tFAW to 50˜80, also change tRRD to 8 or higher ..... it seems this could solve the problem with 4 dimm... (**)
4) adjust memory voltage to XMP values and memory multiplier to 1600MHz (depending on RAM, it could be changed...)
5) put the memory mode to NORMAL or ENHANCE STABILITY. verify if command rate is 2T
Reboot and check in BIOS if the values are ACTUALLY set (in my H87, they only changed after a cold boot: remove power cord - or turn of power switch if you have - for 20 seconds and turn on again).
do a Cold boot and check if the values still there.
then go to OSX/Windows and run some benchmarks. check the timing values inside windows (AIDA, Everest, etc. I don't know how to check in OSX) to see if it still there even if you reboot or cold boot.
You don't need to change voltages or other settings with works well with 2 DIMM, just these two timing values.
(**) these values almost double from memory kits with use double side ram or has 2 and 4 dimm configurations (same model/chip). So it seems theses values have direct relation with memory density. Also, older memory modules (launched before haswell) has 120˜160 tRFC and 28˜40 tFAW, but the new ones (advertising as haswell compatible) has higher values. tRRD is related to tFAW, the minimum possible value is 4 and some 4 dimm kits on gigabyte QVL has tRRD 6, 7 or 8. I recommend 8 for stabilty.
gigabyte bios has bugs, in my case it require a cold boot to change values, but i think it is possible to do manually solve this issue if we understand exactly where the problems is.
share your comments here about this experiment. please.
at least with my memory kit, it seems to be solved. I'm now running 4 DIMM 16GB 1.35v 1600MHz replicating XMP profile at manual mode (but increase tRFC and tFAW) without changing any other voltage parameters for 30 hours free of crashes.
(english is not my natural language)
I collect a lot of information about memory changes from z68/z77 to z87 and found that memory subtimings has changed, and now we have "haswell compatible memory" for some brands. I didnt find all changes but it clear to me that tRFC and tFAW have higher values now.
and comparing some memory brands who has 16GB (2 sticks) and 32GB (4 sticks) on the same model/IC, I also found tRFC and tFAW higher on the 4 sticks kit.
so, first conclusion is: HASWELL NEEDS HIGHER tRFC and tFAW and 4 DIMM needs even HIGHER values.
I dont know how other motherboard brands solve this, but gigabyte still isnt fix the 4 dimm problem on their boards, you can see a few users happy using brand new memories from QVL (gigabyte have a very small ones) but there is a lot of people still getting problems.
I have a old 16GB 4 DIMM memory kit with works fine at 2 DIMM XMP 1600Mhz 1.35v at my H87 board, but wont work at all with 4 DIMM. i try everything: lowering timing/latency, increase System Agent,, IO Digital/Analog voltage and several others tricks without success. But I didnt try on sub-timings values and when I see the values I notice that are VERY LOW tRFC and tFAW compating to other 4 DIMM kit. it seems tRRD is also related to tFAW, so i recommend higher a little (I use 8)
so, if you can try a little experiment with 4 dimm, do this:
1) note (or print/photo) all RAM TIMINGS you are using on XMP profile.
2) disable XMP profile and put memory timing on MANUAL
3) change manually all timings values to the XMP values you printed, but increase tRFC to 280˜310 and tFAW to 50˜80, also change tRRD to 8 or higher ..... it seems this could solve the problem with 4 dimm... (**)
4) adjust memory voltage to XMP values and memory multiplier to 1600MHz (depending on RAM, it could be changed...)
5) put the memory mode to NORMAL or ENHANCE STABILITY. verify if command rate is 2T
Reboot and check in BIOS if the values are ACTUALLY set (in my H87, they only changed after a cold boot: remove power cord - or turn of power switch if you have - for 20 seconds and turn on again).
do a Cold boot and check if the values still there.
then go to OSX/Windows and run some benchmarks. check the timing values inside windows (AIDA, Everest, etc. I don't know how to check in OSX) to see if it still there even if you reboot or cold boot.
You don't need to change voltages or other settings with works well with 2 DIMM, just these two timing values.
(**) these values almost double from memory kits with use double side ram or has 2 and 4 dimm configurations (same model/chip). So it seems theses values have direct relation with memory density. Also, older memory modules (launched before haswell) has 120˜160 tRFC and 28˜40 tFAW, but the new ones (advertising as haswell compatible) has higher values. tRRD is related to tFAW, the minimum possible value is 4 and some 4 dimm kits on gigabyte QVL has tRRD 6, 7 or 8. I recommend 8 for stabilty.
gigabyte bios has bugs, in my case it require a cold boot to change values, but i think it is possible to do manually solve this issue if we understand exactly where the problems is.
share your comments here about this experiment. please.
at least with my memory kit, it seems to be solved. I'm now running 4 DIMM 16GB 1.35v 1600MHz replicating XMP profile at manual mode (but increase tRFC and tFAW) without changing any other voltage parameters for 30 hours free of crashes.
(english is not my natural language)
