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Author Topic: Lower memory clock does not improve mining speed  (Read 4641 times)
chungenhung
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May 18, 2011, 04:38:39 PM
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So many people say lower memory clock speed up mining speed.
I am using Win7 x64 with 11.4 drivers and the default SDK (I am guessing it is 2.4. How to check it to make sure?).
Running Phoenix 1.47 and poclbm kernel.

With sapphire 5850, core at 840, I lowered the memory clock from 1000 to 300.
What I saw was a 3-6MH/s DROP in hashing rate. This is opposite of what everyone else is getting.

Just to make sure, how do you guys measure the hash rate?
I just look at the command line outputs, where it updates the hashrate every second or so.

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JWU42
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May 18, 2011, 05:00:27 PM
 #2

Try using an older driver and SDK (2.1 ideally).

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May 18, 2011, 05:30:59 PM
 #3

Try this, it may help.
mem clk = Core clk /3 + 14
in your case, (840/3) + 14 = 294
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May 18, 2011, 05:43:59 PM
 #4

Also try different worksizes, I found the optimal setting can vary depending on memory clock speed.
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May 18, 2011, 05:44:37 PM
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try inthe 200 range... it seems to depend on the card, so there is no set formula

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chungenhung
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May 18, 2011, 06:32:46 PM
 #6

Actually I did try various memory clock speeds.
Here is the list:
1200, 1100, 1000, 800, 700, 600, 500, 400, 300.
All have almost zero effect on hash rate.
I cannot go under 300, as it will freezes Windows.

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May 18, 2011, 06:42:45 PM
 #7

i never experienced any improvement in mining speed when lowering memory-clocks,
the reason i do it anyway is simply, that it
a) needs less power and
b) creates less heat
there's no reason not to lower memory-clocks.

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May 18, 2011, 09:32:17 PM
 #8

Might not improve mining speed, but it lowers 6950 temperatures by 4c with almost no impact on Hash/s. Can overclock core some more after that = profit.

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May 18, 2011, 09:48:57 PM
 #9

Actually I did try various memory clock speeds.
Here is the list:
1200, 1100, 1000, 800, 700, 600, 500, 400, 300.
All have almost zero effect on hash rate.
I cannot go under 300, as it will freezes Windows.

most people that reports increase claim that sweetspot is only couple mhz wide, so your experience tells us nothing really
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May 18, 2011, 11:32:28 PM
 #10

My sweetspot for my 6870 1020 core is 344 mem.... it gives me 10Mh/s increase and a 10C decrease.... it is quite awesme

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Kerr0r
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May 18, 2011, 11:44:07 PM
 #11

This may mark me as a total newbie but...
How are people setting their memory clocks? CCC won't let me set mine lower than 450MHz. Running dual 4870's.
Jaime Frontero
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May 18, 2011, 11:48:25 PM
 #12

This may mark me as a total newbie but...
How are people setting their memory clocks? CCC won't let me set mine lower than 450MHz. Running dual 4870's.

what operating system?
jedi95
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May 18, 2011, 11:48:45 PM
 #13

So many people say lower memory clock speed up mining speed.
I am using Win7 x64 with 11.4 drivers and the default SDK (I am guessing it is 2.4. How to check it to make sure?).
Running Phoenix 1.47 and poclbm kernel.

With sapphire 5850, core at 840, I lowered the memory clock from 1000 to 300.
What I saw was a 3-6MH/s DROP in hashing rate. This is opposite of what everyone else is getting.

Just to make sure, how do you guys measure the hash rate?
I just look at the command line outputs, where it updates the hashrate every second or so.

With SDK 2.4 you should also try the phatk kernel. (thread is linked in the first post of the Phoenix miner thread, and it's included in 1.48)

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Kerr0r
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May 18, 2011, 11:49:24 PM
 #14

This may mark me as a total newbie but...
How are people setting their memory clocks? CCC won't let me set mine lower than 450MHz. Running dual 4870's.

what operating system?

Win7 x64.
nster
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May 18, 2011, 11:54:38 PM
 #15

This may mark me as a total newbie but...
How are people setting their memory clocks? CCC won't let me set mine lower than 450MHz. Running dual 4870's.

what operating system?

Win7 x64.

http://bitcointalk.org/index.php?topic=4292.0

I'm the one who made underclockng popular lol....

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Kerr0r
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May 18, 2011, 11:57:36 PM
 #16

This may mark me as a total newbie but...
How are people setting their memory clocks? CCC won't let me set mine lower than 450MHz. Running dual 4870's.

what operating system?

Win7 x64.

http://bitcointalk.org/index.php?topic=4292.0

I'm the one who made underclockng popular lol....
Thanks mate. ^^
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