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Author Topic: Lowering mem clock to idle speeds SPEEDS UP Mh/s  (Read 37395 times)
allinvain
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April 11, 2011, 07:18:45 AM
 #41

Hmm, so the anandtech article on the 5870 mentions:
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The specific CRC function used in GDDR5 can detect 1-bit and 2-bit errors with 100% accuracy, with that accuracy falling with additional erroneous bits. This is due to the fact that the CRC function used can generate collisions, which means that the CRC of an erroneous data burst could match the proper CRC in an unlikely situation. But as the odds decrease for additional errors, the vast majority of errors should be limited to 1-bit and 2-bit errors.

Should an error be found, the GDDR5 controller will request a retransmission of the faulty data burst, and it will keep doing this until the data burst finally goes through correctly. A retransmission request is also used to re-train the GDDR5 link (once again taking advantage of fast link re-training) to correct any potential link problems brought about by changing environmental conditions. Note that this does not involve changing the clock speed of the GDDR5 (i.e. it does not step down in speed); rather it’s merely reinitializing the link. If the errors are due the bus being outright unable to perfectly handle the requested clock speed, errors will continue to happen and be caught. Keep this in mind as it will be important when we get to overclocking.

http://www.anandtech.com/show/2841/12
Maybe with higher memory clocks some computation is delayed because the memory needs to retransmit again. This may be the reason some people see increases in performance and others don't. (some people's cards can transmit 100% at the stock speed and other people's can't)

On both my 5870 and 5850, lowering the memory clock decrease hash rate. Does anyone with these 2 cards see the opposite?

Well that's odd...why does it not affect hash rates on the 5970?

My 5970 is currently clocked at 850 Mhz and 300 Mhz memory and currently pulling 318.2 Mhash/s per GPU...can anyone else corroborate this?

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rezin777
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April 11, 2011, 07:37:16 AM
 #42

On both my 5870 and 5850, lowering the memory clock decrease hash rate. Does anyone with these 2 cards see the opposite?

Yes, I get a noticeable increase with both of those cards.
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April 11, 2011, 11:31:50 AM
 #43

XFX 5870 here

I dropped the memory clock to 300.

Mh/s is holding at 336 now where as before it was fluctuating from 330. My temp appears to have dropped by 5c. I'll do more testing but it's looking good so far.

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April 11, 2011, 09:55:32 PM
 #44

XFX 5870 here

I dropped the memory clock to 300.

Mh/s is holding at 336 now where as before it was fluctuating from 330. My temp appears to have dropped by 5c. I'll do more testing but it's looking good so far.
On both my 5870 and 5850, lowering the memory clock decrease hash rate. Does anyone with these 2 cards see the opposite?

Yes, I get a noticeable increase with both of those cards.

What miners/OS/Catalyst/opencl are you guys running?
rezin777
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April 12, 2011, 12:21:55 AM
 #45

What miners/OS/Catalyst/opencl are you guys running?

Newest poclbm / Win7 64 / 11.3 / whatever is included with 11.3
allinvain
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April 12, 2011, 01:26:30 AM
 #46

What miners/OS/Catalyst/opencl are you guys running?

Newest poclbm / Win7 64 / 11.3 / whatever is included with 11.3

11.3 uses SDK 2.3 (ie opencl) as far as I know..

I've go the same setup btw.

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April 12, 2011, 01:34:04 AM
 #47

Glad it is working for so many of you

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April 12, 2011, 10:33:17 AM
 #48

OS   Win7 x64
Cat   11.3
SDK   v2.4

dishwara
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April 14, 2011, 12:38:41 AM
 #49

Please try this & give confirmed confirmations.

The MAXIMUM STABLE CONSTANT hash/s is obtained by a formula which i tried & found out for my HD6870. Instead of varying hash/s, it gives some what constant hash/s
Memory clock = (core clock /3) + 14
Please try, test & confirm with your results & please put your data here with your Graphics card & hash/s you get (you can add OS, 32 or 64, catalyst version & stream or APP version also).

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EPiSKiNG
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April 14, 2011, 03:17:25 AM
 #50

Please try this & give confirmed confirmations.

The MAXIMUM STABLE CONSTANT hash/s is obtained by a formula which i tried & found out. Instead of varying hash/s, it gives some what constant hash/s
Memory clock = (core clock /3) + 14
Please try, test & confirm with your results & please put your data here with your Graphics card & hash/s you get (you can add OS, 32 or 64, catalyst version & stream or APP version also).

Donations & loans are always welcome.
Thanks.


2x5870 950core, 330mem: 316MH/s each
2x5870 950core, 1000mem: 358 MH/s each

-EP

YOU CAN TRUST ME! EPiSKiNG-'s COINS!! BUYING / SELLING BTC - USA --- View my OTC Trading Feedback!!
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nster
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April 15, 2011, 08:03:58 AM
 #51

Please try this & give confirmed confirmations.

The MAXIMUM STABLE CONSTANT hash/s is obtained by a formula which i tried & found out for my HD6870. Instead of varying hash/s, it gives some what constant hash/s
Memory clock = (core clock /3) + 14
Please try, test & confirm with your results & please put your data here with your Graphics card & hash/s you get (you can add OS, 32 or 64, catalyst version & stream or APP version also).

Donations & loans are always welcome.
Thanks.


thanks!!!! However my numbers are different...

OS: Windows 7 Pro 64-bit
Cat 11.4 stream 2.4
Card: 6870

Hashrate @ 300 1020 core= 263500 kh/s
310 = 264400 kh/s
320 = 265500 kh/s
330 = 266300 kh/s
340 = 266800 kh/s
350 = 266750 kh/s (varies a bit more)
354 (1020/3 +14) = 266500 kh/s
360 = 265500 kh/s

After further testing:
341 = 268100 kh/s
342 = 267100 kh/s
343 = 267350 kh/s
344 = 267150 kh/s
345 = 267000 kh/s
346-349 = gradually down until 266750 kh/s

So best mem clocks are 341... 341 = coreclock/3 + 1

Trying with 999 core now

300 = 259000 kh/s
330 = 261550 kh/s
334 (999/3 + 1) = 261500 kh/s
340 = 261600 kh/s
347 (999/3 + 14) = 260800 kh/s

at this point I can see the /3 is the wrong correlation with the core clock.

337 = 261000 kh/s
338 = 261500 kh/s
339 = 261600 kh/s
340 = 261600 kh/s
341 = 261650 kh/s
342 = 261500 kh/s
343 = 261500 kh/s


So far, it seems 341 is a very good mem clock to start at

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dishwara
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April 15, 2011, 02:51:45 PM
 #52

i am running in windows 7  32bit aero enabled , 6870

at present 1042 core & 361 mem with 100% fan & 73C temp
getting 271-275 Mhash/s
with flags, -v -w128 -f1
nster
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April 15, 2011, 06:01:12 PM
 #53

-v -w128 -f 120 here

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dishwara
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April 16, 2011, 12:08:58 AM
 #54

as i said in some posts before, which i forgot, due to get mine more, 1042 crashed.

so now back to 1038 core & 360 mem, 100% fan with temp 70C
268- 273 Mhash/s , -v -w128 -f1
PiGames
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April 16, 2011, 02:37:42 PM
 #55

Bump b/c it seems to work =)
Using afterburner I lowered the memclock on my 6850 to 300 and raised my core clock to 900..seems to be the sweet spot for my card.
Im up to 191-193 Mhash/s from 169-172
allinvain
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April 16, 2011, 04:34:00 PM
 #56

Bump b/c it seems to work =)
Using afterburner I lowered the memclock on my 6850 to 300 and raised my core clock to 900..seems to be the sweet spot for my card.
Im up to 191-193 Mhash/s from 169-172

So essentially you were able to maintain the same thermal profile yet increase your performance Tongue ? If so then congrats!

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April 18, 2011, 10:05:15 PM
 #57

Is there anyway to run MSI Afterburner to automatically Over clock of memory also?
I did my best & it loads core clk as 1038 on startup, but memory 1050 only, then i move the slider to minimum, for me 525, apply & restart MSI AF.
Restarting shows core as 900 & mem as 1050, but clicking saved profile, brings it to 1038/360.
I want MSI AF or if any other software there to automatically apply OC, so no human interaction needed to mining.
Tried with MSI AF 2.0 & 2.1

EDIT: With out loosing warranty or guarantee & also no flashing & only software based.
rezin777
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April 19, 2011, 01:10:30 AM
 #58

Is there anyway to run MSI Afterburner to automatically Over clock of memory also?
I did my best & it loads core clk as 1038 on startup, but memory 1050 only, then i move the slider to minimum, for me 525, apply & restart MSI AF.
Restarting shows core as 900 & mem as 1050, but clicking saved profile, brings it to 1038/360.
I want MSI AF or if any other software there to automatically apply OC, so no human interaction needed to mining.
Tried with MSI AF 2.0 & 2.1


Flash the BIOS with whatever settings you wish.
dishwara
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April 19, 2011, 03:33:30 AM
 #59

Is there anyway to run MSI Afterburner to automatically Over clock of memory also?
I did my best & it loads core clk as 1038 on startup, but memory 1050 only, then i move the slider to minimum, for me 525, apply & restart MSI AF.
Restarting shows core as 900 & mem as 1050, but clicking saved profile, brings it to 1038/360.
I want MSI AF or if any other software there to automatically apply OC, so no human interaction needed to mining.
Tried with MSI AF 2.0 & 2.1


Flash the BIOS with whatever settings you wish.

I can't loose my warranty or guarantee.
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April 19, 2011, 11:05:03 AM
 #60

if you're overclocking ... you're already losing your warranty

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