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Author Topic: Underclocking my memory gives massive performance drops?  (Read 1276 times)
Tr0gledyte
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June 25, 2011, 04:51:12 PM
 #1

Posted this in the newbie forum first but got no replies.

I'm currently running my HD6850 at 925/1150 and I get 230-235 Mhash/s. If I lower the memory clock using MSI Afterburner, my hash rate drops correspondingly. If I go all the way down to 300 Mhz, my hash rate drops to around 160 Mhash/s. I have tried tons of different memory clocks in steps of 50-100 between 300 and 1150 and a higher memory clock always gives me a significantly better hash rate. What's up with that? Seems like I'm the only one experiencing this problem.

I use Diablominer with -v 19 -w 128 (gave me the best performance) and -f 30 (so I can play games if needed without closing my miner, when not playing games this setting does not affect my performance).

Anyone know what's up? I'd like to be able to underclock my memory without destroying my hash rate.
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Yatta99
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June 25, 2011, 05:03:12 PM
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The purpose of underclocking the memory clock is so that you can overclock the core clock and not fry the card. The combination of lowering one while raising the other will give you an overall higher hash rate while keeping temperature the same or not much higher (and in some cases, slightly lower). Just be careful and only bump the core clock up in small amounts... a dead gpu doesn't hash  Cry

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Tr0gledyte
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June 25, 2011, 05:06:33 PM
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The purpose of underclocking the memory clock is so that you can overclock the core clock and not fry the card. The combination of lowering one while raising the other will give you an overall higher hash rate while keeping temperature the same or not much higher (and in some cases, slightly lower). Just be careful and only bump the core clock up in small amounts... a dead gpu doesn't hash  Cry

I thought people lowered the memory clock because it didn't affect their hash rate while simultaneously reducing heat and power consumption.

I don't see any core overclock pushing my hash rate from 160 Mhash/s over 230 Mhash/s... Stock core is 775, so 925 is already a fairly big overclock, and at 925/300 I get 160 Mhash/s.
fitty
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June 25, 2011, 05:37:20 PM
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The purpose of underclocking the memory clock is so that you can overclock the core clock and not fry the card. The combination of lowering one while raising the other will give you an overall higher hash rate while keeping temperature the same or not much higher (and in some cases, slightly lower). Just be careful and only bump the core clock up in small amounts... a dead gpu doesn't hash  Cry

I thought people lowered the memory clock because it didn't affect their hash rate while simultaneously reducing heat and power consumption.

I don't see any core overclock pushing my hash rate from 160 Mhash/s over 230 Mhash/s... Stock core is 775, so 925 is already a fairly big overclock, and at 925/300 I get 160 Mhash/s.

Not every card goes down to 300. Some go down to 600. Some don't do well at all when you underclock the memory. It depends on your system and your card.

If it doesn't help then don't do it. =) Your hash rates are pretty good I wouldn't sweat it.
padrino
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June 25, 2011, 06:36:53 PM
 #5

If you drop to 300 use -w 256 to get some Mh/s back.

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Tr0gledyte
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June 25, 2011, 07:46:36 PM
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If you drop to 300 use -w 256 to get some Mh/s back.

This made it drop further to 125 Mhash/s and it makes my Windows 7 Aero interface lag.
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June 26, 2011, 03:42:29 AM
 #7

Just find the sweetspot wherever that is without burning the thing up.

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