DRAM Command Rate Explained

[joehall2000]

I can't find any issue discuss which one is faster ?
I want to raise the performance of my pc. If all parameters are fixed except the timing of the rams(ddr3-1333 2GB x2).One is ddr3-1333 9-9-9-27-2T, the other one is ddr3-1333 7-7-7-20-1T. I want to know which one is better if both run stablely ? Thanks.

 

[Leaps-from-Shadows]

Assuming both are 100% stable, lower timings are better. The one with 7-7-7-20-1T timings will out-perform the other by a small margin.

 

[joehall2000]

Assuming both are 100% stable, lower timings are better. The one with 7-7-7-20-1T timings will out-perform the other by a small margin.

Thanks a lot for your response. And, how about ddr3-1066 7-7-7-20-1T vs ddr3-1333 9-9-9-27-2T ? It's the condition when the cpu support ddr3-1066 with the ram ddr3-1333. I guess the former condition still beat the later, doesn't it?

 

[jaquith]

Command Rate (CMD) is the Delay between chip select and command, or the number of clock cycles needed to send data.

On 1333 maybe 1600 1T {aka 1N} can be used but if it's too fast it can both cause errors and if the data is needed to be resent can actually take longer. MOST current DDR3 RAM has a CMD of 2T {2N}.

Test both, 1T & 2T with Super PI and Memtest; if it's faster + errors then go back to 2T.

Most of my rigs are set to 2T with DDR3 1600. edit: Where I use 1T -- it's tested big-time! 😉

 

[Leaps-from-Shadows]

...how about ddr3-1066 7-7-7-20-1T vs ddr3-1333 9-9-9-27-2T ?

Speed matters more than timings do. The 1333 RAM with higher timings will beat the 1066 RAM with lower timings.

 

[joehall2000]

Speed matters more than timings do. The 1333 RAM with higher timings will beat the 1066 RAM with lower timings.

Thank you very much.
The situation i face is the laptop with the combination of p6200 + ddr3-1333(999-27-2t). The ram's frequency drop to 1066(777-20-1t). There isn't any choice to adjust the ram's frequency or timing. I got no way to compare which timing will get better performance.
So, i should buy the ram that runs 1066 with timing of 777-20-1t(or 2t) because it is cheaper than the ram that runs 1333(999-27).

 

[jaquith]

You couldn't perceive the difference between 1333 9-9-9-27-2T & 1066 7-7-7-20-1T unless you're a 'Borg.' Buy whatever your Notebook specs dictate.

Speed matters to a 'point' however with the Sandy Bridge fixed 'BCLK' the advantages of High Frequency + Low CAS are minimized. Meaning 1600 CAS 8/9 vs 2133 CAS 9 performs about the same - exceptions are in some multi-tasking situations.

 

[joehall2000]

You couldn't perceive the difference between 1333 9-9-9-27-2T & 1066 7-7-7-20-1T unless you're a 'Borg.' Buy whatever your Notebook specs dictate.

http://i1013.photobucket.com/albums/af254/Jaquith/CAS_Frequncy_Chart.png

Speed matters to a 'point' however with the Sandy Bridge fixed 'BCLK' the advantages of High Frequency + Low CAS are minimized. Meaning 1600 CAS 8/9 vs 2133 CAS 9 performs about the same - exceptions are in some multi-tasking situations.

Via the chart you provided, i think you want to tell me that the intercalated value of ddr-1066(cas=7) is possibly the same as ddr-1333(cas=9), don't you?

 

[jaquith]

RAM 1333 10666 MB/s BUT Slower wait times vs RAM 1066 8533 MB/s BUT Faster wait times; so the effective processed data is close wash.

Visual - Transfer + Waiting '...' (CAS)
1333 Fast.........Fast.........Fast.........
1066 Slowr.......Slowr........Slowr.......

Further, the speed of your RAM on your Notebook is that last 'speed barrier' you need to worry about. It's HDD (100~120 MB/s) and iGPU are like molasses to your RAM's (8533~10666 MB/s) air in slowing you down.

IF you '?????' Notebook only supports 1066 then it's pointless to get faster RAM. To confuse the issue more, comparing (2) sets of 1333 9-9-9-24-2T vs 1333 9-9-9-24-2T will not achieve identical results -- Quality of the IC used. If the 1066 and 1333 are the same $ then choose the 1333 {if supported} otherwise you're really worrying over nothing. Compatibility & Quality is the #1...#100 objective then #101 Frequency + #102 CAS.

Here's a real world comparison; 1333 running close to 1866:
Comparison Module #1: Mushkin Redline 996805 6-8-6-24 1600MHz
Comparison Module #2: G.Skill Pi Series 7-8-7-24 1600MHz
Comparison Module #3: Mushkin 998687 8-9-8-24 1866MHz
Comparison Module #4: Corsair Dominator TR3X6G1600C8D 8-8-8-24 1600MHz
Comparison Module #5: Kingston HyperX T1 9-9-9-27 1600MHz
Comparison Module #6: Mushkin Blackline 998677B 7-7-7-20 1333MHz
Comparison Module #7: Patriot Viper II Sector 7 9-9-9-27 1800MHz

 

[joehall2000]

RAM 1333 10666 MB/s BUT Slower wait times vs RAM 1066 8533 MB/s BUT Faster wait times; so the effective processed data is close wash.

Visual - Transfer + Waiting '...' (CAS)
1333 Fast.........Fast.........Fast.........
1066 Slowr.......Slowr........Slowr.......

Further, the speed of your RAM on your Notebook is that last 'speed barrier' you need to worry about. It's HDD (100~120 MB/s) and iGPU are like molasses to your RAM's (8533~10666 MB/s) air in slowing you down.

IF you '?????' Notebook only supports 1066 then it's pointless to get faster RAM. To confuse the issue more, comparing (2) sets of 1333 9-9-9-24-2T vs 1333 9-9-9-24-2T will not achieve identical results -- Quality of the IC used. If the 1066 and 1333 are the same $ then choose the 1333 {if supported} otherwise you're really worrying over nothing. Compatibility & Quality is the #1...#100 objective then #101 Frequency + #102 CAS.

Thank you very very much.

 

[sagara-kun]

You couldn't perceive the difference between 1333 9-9-9-27-2T & 1066 7-7-7-20-1T unless you're a 'Borg.' Buy whatever your Notebook specs dictate.



Speed matters to a 'point' however with the Sandy Bridge fixed 'BCLK' the advantages of High Frequency + Low CAS are minimized. Meaning 1600 CAS 8/9 vs 2133 CAS 9 performs about the same - exceptions are in some multi-tasking situations.

fom wat i've read the lower the better x-x-x-x...so wat should i do?? which one is better for me

default:
8-8-8-24 1T
dram frequency= 650 mhz
fsb : dram= 1:5

@1066mhz
7-7-7-21 1T
dram frequency= 535 mhz
fsb : dram= 1:4

@1333mhz
9-9-9-24 1T
dram frequency= 665 mhz
fsb : dram= 1:5

ram = 4ddr3 1333mhz, multiplier = x16.0

 

[Nafryti]

this is nice to know and all, but what do i do when my AMD RG2133 says Command Rate 3N???

furthermore, does anyone know the complete list of timings as my ASUS Crosshair V Formula-Z is mentally challenged when it comes to the AMP settings.

I know this to be a fact, because my system becomes glitchy when the motherboard decides to drop the ball on the timings and request me input them manually, i once knew of the timings but now i cannot find them.

PLEASE! if you see this within minutes of my post i am not able to reply and would love you to join my teamspeak to walk me through it as i will be on there with my iPod Touch.

 

[Nafryti]

how the what?! why is my problem selected as a "Best Solution"?! or is this a way to highlight a problem? I am still completely oblivious to timings, regardless of what the TomsHardware tutorial says, it has left me with the same amount of questions i started with.

 

[Tradesman1]

how the what?! why is my problem selected as a "Best Solution"?! or is this a way to highlight a problem? I am still completely oblivious to timings, regardless of what the TomsHardware tutorial says, it has left me with the same amount of questions i started with.

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