I have 8GB of F3-16000CL9D-4GBRH running at DDR3 1600, BCLK 133 on a Gigabyte GA-P55M-UD2 MB, BIOS ver. = f5K. All voltages are set to auto in BIOS: with BCLK=133, setting VDIMM to 1.65V makes no difference.
Timings from bootup: 7-7-7-16, with tRC=23, tRFC=50, RTL=42 (RTL=41 fails POST) and 1T (this reduces latency about 10% from 2T). These are values set in the BIOS. I picked tRAS=16 because supposedly tRAS=tCL+tRCD+2.
According to SiSoft Sandra, my bandwidth runs in the mid-19 GB/s at DDR3-1600. The bandwidth varies with the mem rate, up to around 24GB/s at DDR3-2000. At DDR3-1600 my combined memory latency=66.2ns, with a power factor of 51.8. The scores vary a bit, of course, but this is the best I have done so far. And it is pretty good: working to get timings down has decreased my latency about 10%.
IMO the results are very, very good. When I get a better cooler, I will crank up the BCLK to 166 to get DDR3 2000. I have tried it out and it works well, except for the temps.
So what is my first question?
I have used CPU-Tweaker to vary the tRAS from 16 to 25 -- higher than tRC -- without making and substantial difference to the results.
In theory, I should either freeze my machine (setting tRFC=45 did that) or cause worsening of the results, but neither happened. I even set tRAS=tRC in BIOS with continued good results.
In theory, this should not be possible. Supposedly tRAS+tRP=tRC, which is why I set tRC=23 in the BIOS.
So, question 1: what is going on here?
My hypothesis is that by setting tRC=23, I am holding tRAS to 16. In essence, tRC seems to be driving tRAS when the settings conflict. But is that right?
Question 2: what is up with tRFC?
Setting it from 50 to 60 with 7-7-7-23 makes no difference to latency. Setting it to 74 or even 88 just barely nudges up the latency by about a nanosecond.
Should I look at other settings? Or should I accept these rates as about the best I am going to do at this BCLK?
Thanks.
Timings from bootup: 7-7-7-16, with tRC=23, tRFC=50, RTL=42 (RTL=41 fails POST) and 1T (this reduces latency about 10% from 2T). These are values set in the BIOS. I picked tRAS=16 because supposedly tRAS=tCL+tRCD+2.
According to SiSoft Sandra, my bandwidth runs in the mid-19 GB/s at DDR3-1600. The bandwidth varies with the mem rate, up to around 24GB/s at DDR3-2000. At DDR3-1600 my combined memory latency=66.2ns, with a power factor of 51.8. The scores vary a bit, of course, but this is the best I have done so far. And it is pretty good: working to get timings down has decreased my latency about 10%.
IMO the results are very, very good. When I get a better cooler, I will crank up the BCLK to 166 to get DDR3 2000. I have tried it out and it works well, except for the temps.
So what is my first question?
I have used CPU-Tweaker to vary the tRAS from 16 to 25 -- higher than tRC -- without making and substantial difference to the results.
In theory, I should either freeze my machine (setting tRFC=45 did that) or cause worsening of the results, but neither happened. I even set tRAS=tRC in BIOS with continued good results.
In theory, this should not be possible. Supposedly tRAS+tRP=tRC, which is why I set tRC=23 in the BIOS.
So, question 1: what is going on here?
My hypothesis is that by setting tRC=23, I am holding tRAS to 16. In essence, tRC seems to be driving tRAS when the settings conflict. But is that right?
Question 2: what is up with tRFC?
Setting it from 50 to 60 with 7-7-7-23 makes no difference to latency. Setting it to 74 or even 88 just barely nudges up the latency by about a nanosecond.
Should I look at other settings? Or should I accept these rates as about the best I am going to do at this BCLK?
Thanks.
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