AMD, un-/ganged, what's faster at S@h ?


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Profile [seti.international] Dirk SadowskiProject donor
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Message 1030268 - Posted: 2 Sep 2010, 20:40:47 UTC

Hello community! :-)


At AMD systems, you can choose un-/or ganged system RAM mode.

What's faster here at SETI@home?

At CPU WUs..

At GPU WUs.. (because the system RAM is also important for CUDA, faster system RAM -> faster CUDA)


Someone made a test?


Thanks!

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Message 1030273 - Posted: 2 Sep 2010, 21:07:55 UTC - in response to Message 1030268.

Well that is some word, I've never heard.
Ganged v.s. UN-Ganged

Do you mean 1 or 2 (or3) channel, ERROR Correction?

Ganged Memory.

Ganged Memory.

Anyway, here's something to read :-)

Keep on CRUNCHING

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Message 1030278 - Posted: 2 Sep 2010, 21:36:35 UTC - in response to Message 1030273.

As ganged would mean Dual-Channel, them I'd say ganged.
And memory with low latancy and high speed.(Have my OCZ sticks running at 400MHz, with 5.5.5.14.-1T)FSB:DRAM=5:6.

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Message 1030280 - Posted: 2 Sep 2010, 21:52:38 UTC

"Ganged" and "Unganged" seems to be a new term on some recent motherboard BIOSes.

On mine, the help for that option claims that "Unganged" gives higher performance.


Now, can anyone explain the technicalities please?

Happy crunchin',
Martin

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Message 1030282 - Posted: 2 Sep 2010, 22:03:10 UTC

The way i understand it both are technically multi channel modes. These only apply to multi core machines...in ganged mode all processor cores have direct access to all memory, in nonganged the cores split up which memory addresses tehy have direct access to...I've also heard that nonganged allows for different memory timings on different slots. There is a lot of confusion to the term.


Ganged used to mean that a pair of 64 bit controllers could be used together to transfer to memory at 128 bits.

http://ixbtlabs.com/articles3/cpu/amd-phenom-x4-9850-ganged-unganged-p1.html

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Message 1030283 - Posted: 2 Sep 2010, 22:11:17 UTC

The newer Phenoms have 2 Memory-Controller on the cpu-die.

ganged: the memory controller behave like one controller, but with a 128 bit wide data-bus to the memory.

unganged: now the 2 controller work independent from each other, but only with a 64 bit wide bus.

from what i have read, the differences between this 2 modes are so small (vary in 0.x % area), that not moving the mouse-curser brings u more usable cpu-cycles :-))
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Message 1030289 - Posted: 2 Sep 2010, 23:03:02 UTC

Depends on what AMD chip you are using ...

Basically

Phenom and Phenom(II) work best with 2GB sticks and unganged
X2 work best 1GB sticks and ganged

Not much difference between ganged and unganged unless you are over clocking then it helps quite a bit with stability
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Message 1030290 - Posted: 2 Sep 2010, 23:08:42 UTC

Ganged mode gives me 10 minutes faster crunching on avg.
2:00 vs 2:10 ...
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Message 1030405 - Posted: 3 Sep 2010, 8:37:33 UTC

That caught me out when I built new rigs recently with Athlon II/Phenom II quads.

It's just AMD trying to differ from the mainstream: - Single vs Dual channel.

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Message 1030424 - Posted: 3 Sep 2010, 13:57:01 UTC

Thanks to all for replies!

I looked a little bit around..


At least for Phenom II CPUs:

If you have un-/or ganged mode, you have always dual-channel.

Unganged mode could give improvement at multi-thread apps.
Ganged for single-thread apps.

AFAIK, S@h have single-thread apps, so ganged mode could/should give more performance.


I have since a few hours unganged mode in BIOS disabled.
CPU-Z show ganged mode and dual-channel.

If the Inet connection of SETI@home is again enabled, after a few hours (the last time ~ 5 hours) the results of 3 days are all UL/reported, I could see if this help.


Maybe this is the AMD trick for to beat the Intel's.. X-D
(Because they are always bullied from Intel..)

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Message 1030559 - Posted: 3 Sep 2010, 22:52:48 UTC
Last modified: 3 Sep 2010, 23:29:34 UTC

Hmm.. strange..

After a few hours in ganged RAM mode, my machine made an auto reboot..

I changed only the RAM slots from #1 + #4 to #1 + #2. I read about that I should use the first slots of each channel.
And I disabled the unganged RAM mode, for to have ganged RAM mode.
That was all.

If I get again an auto reboot, it's the RAM slots, or overheat of the RAM, because now they are very close..

They are 2x 2 GB OCZ DDR2 1066/5-5-5-18 @ 1.8 V (low voltage) RAMs (OCZ2P1066LV4GK).. maybe little buggy..?

:-/


[EDIT: Ahh.. BTW.. I'm back to unganged.. for to test if again an auto reboot..]
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Message 1030584 - Posted: 3 Sep 2010, 23:37:40 UTC - in response to Message 1030559.

Yes you should have (assume 2 x 2GB sticks) one in first slot for channel 0 and one in first slot for channel 1

Which slot is which depends on the MB .. and a lot of times the manual for XYZ MB is wrong as to which slot belongs to which channel. (my MB manual shows slots 1 and 2 as channel 0 and slots 3 and 4 as channel 1 .. which is wrong ... in fact it is slots 1 and 3 on channel 0 and slots 2 and 4 on channel 1 ... so double check)

So I have 1 x 2GB stick in slot 1 and 1 x 2GB is slot 2 ... being 1 2GB stick for each channel ... and run as unganged.

OCZ is normaly pretty good memory. I assume you are showing memory as 1066 in CPU ID .. meaning Dram Freq. shows as ~ 533mhz, type DDR2 and channels # as dual.

You may want to consider bumping your memory voltage up a small amount to say 1.95v as that can help, it did with my Phenom running OCZ memory

For stability in the end with my Phenom II X4 940 I found running unganged was best with a bump in memory voltage to 2.1v, a little looser memory timings with the memory set to run as 535mhz to get 1066 dual channel (this is with Corsair memory not OCZ).


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Message 1030950 - Posted: 4 Sep 2010, 20:28:21 UTC - in response to Message 1030584.
Last modified: 4 Sep 2010, 20:30:04 UTC

I have a MSI K9A2 Platinum, which was for ~ 2 years the only mobo with 4x PCIe 2.0 x8 slots (max CUDA performance).. :-)
So I could add 4x GTX260..

On mobo I see DIMM #1, #2, #3, #4 - from left to right. And channel one and channel two with different colors.
#1 #3 channel one and #2 #4 channel two.
So the RAMs are in #1 and #2.

Yes, they are as 533.x MHz in CPU-Z.

On the OCZ RAMs is a sticker with @ 1.8 V. On the OCZ site (OCZ2P1066LV4GK. AFAIK no longer available for to buy - so I need to take care ;-) stay, OCer can use 1.85 V (this is meant with EVP ?).

I read in the internet about that some gave 1.9 V and they were cooked/damaged.
But I don't know if this is true.. you can read a lot of nonsense in the internet.. ;-)

I ordered inter alia 3x 40x40x10 fans for to make my own active RAM cooler.
If installed, maybe will test the 1.85 V and ganged RAM mode.
Maybe with littel bit more V the ganged RAM mode work?


I read also about, that if you have a Phenom II X4 you should not use more than 1.8, or 2.0 V at the system RAM - depend where you read..
If > 1.8 V (2.0 V) you will cook/damage the integrated memory controller of/in the CPU.
I looked at the AMD site, but didn't found infos about, but maybe I looked not at the right places.
What you (all) think about?
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Message 1030973 - Posted: 4 Sep 2010, 21:57:19 UTC - in response to Message 1030950.

EVP = enhanced voltage protection ... fluff? in any case because of the RAM warranty don't set ram voltage higher than 1.85v.

with regards to the ganged and unganged, relative to memory channels on my X4 940 and my MB I have found the following.

With 1 2xGB stick in each channel (meaning slots 1 and 2) ganged (synthetic 128 bit path) would run ok for awhile but every so often there would be an "auto" reboot ... unganged (64 bit path) did not have this problem.

From talking to the memory guy (a back roomer eng.) it was suggested that ganged would possibly work ok with both 2GB sticks on the same channel (however most MB don't like this for dual mode) ... but that it was better to utilize 2 channel at 64 bit rather than 1 channel as sythetic 128 bit.

I did try ganged with all 4 slots filled (all be it with 1GB sticks) and stability was worse (of course a lot of that has to do with the memory / MB / CPU combination)

What I was lead to believe in the end was that the X4 940's on chip memory controler left some things to be desired.

So I decided just to be happy with unganged mode, memory running at 1066 and no out of the "blue" re boots
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Message 1031484 - Posted: 6 Sep 2010, 22:27:02 UTC - in response to Message 1030973.
Last modified: 6 Sep 2010, 22:32:36 UTC

Hmm.. strange, why the memory guy say 2x 2GB RAMs (each channel) and ganged will work and it don't work..?

Hmm.. maybe 64bit OS?

------------------------------------------------------------

IIRC, MaGNeT (a.k.a. BlueTooth76) have a Phenom II X6 and ganged work on his system.

Please give your system specs - CPU, mobo, RAM, voltages?

And you never see reboots or something similar?
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Message 1031514 - Posted: 7 Sep 2010, 2:04:08 UTC

I'm getting ready to build a Win XP 32 bit system like this;
Athlon II X4 630 (4 x 2.8GHz - 2MB Cache - 4000MHz FSB)
Gigabyte M68M-S2P/W
(2) DDR2 800 1 Ghz KHX6400D2LLK2 Ram.
Should I go with Ganged or Un-ganged?
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Message 1031576 - Posted: 7 Sep 2010, 10:07:31 UTC - in response to Message 1031514.

I'm getting ready to build a Win XP 32 bit system like this;
Athlon II X4 630 (4 x 2.8GHz - 2MB Cache - 4000MHz FSB)
Gigabyte M68M-S2P/W
(2) DDR2 800 1 Ghz KHX6400D2LLK2 Ram.
Should I go with Ganged or Un-ganged?



That's not a bad cpu. Built an htpc with one with gigyabyte MA790XT-UD4P mobo for the wife & using ganged mode.

Athlon II 630 host

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Message 1031606 - Posted: 7 Sep 2010, 14:48:09 UTC - in response to Message 1031576.

My personal experiences with ganged vs unganged is that its easier to get the machine stable in ganged mode.

You can run tighter memory timings and also faster memory clocks.

This shouldn't be so, but on my system it is.

The difference I'm seing between the two in crunching times are very small (with same settings), but the better settings ganged mode allows me to run with, gives me the best crunching times in ganged mode.

So my advice is to use Ganged mode.

But with other hardware peoble will get other results, so its not easy giving final advice.
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Message 1031793 - Posted: 8 Sep 2010, 12:55:59 UTC
Last modified: 8 Sep 2010, 13:03:22 UTC

Maybe it would be well to make an overview with systems and if it's possible to let run unganged (standard) and ganged system RAM mode.
Maybe then the other could find a way for to optimize their system for un-/ganged RAM mode..
Ganged RAM mode should be faster with single-thread applications (S@h).


AMD Phenom II X4 940 BE (standard @ 3.0 GHz)
MSI K9A2 Platinum
OCZ 2x 2GB DDR2 1066/5-5-5-18 @ 1.8 V (standard settings, low voltage RAM)
4x GTX260-216 (manufacturer OCed)
WinXP Home x86 Edition (32bit)

Full loaded S@h:
Unganged: YES
Ganged: NO (auto reboot)


(For example: Maybe if I increase the RAM voltage, ganged is possible? ;-)
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Message 1031864 - Posted: 8 Sep 2010, 18:00:41 UTC - in response to Message 1031793.

Maybe it would be well to make an overview with systems and if it's possible to let run unganged (standard) and ganged system RAM mode.
Maybe then the other could find a way for to optimize their system for un-/ganged RAM mode..
Ganged RAM mode should be faster with single-thread applications (S@h).


AMD Phenom II X4 940 BE (standard @ 3.0 GHz)
MSI K9A2 Platinum
OCZ 2x 2GB DDR2 1066/5-5-5-18 @ 1.8 V (standard settings, low voltage RAM)
4x GTX260-216 (manufacturer OCed)
WinXP Home x86 Edition (32bit)

Full loaded S@h:
Unganged: YES
Ganged: NO (auto reboot)


(For example: Maybe if I increase the RAM voltage, ganged is possible? ;-)


Rig name: "Crunchy"
OS: Win 7 x64
MB: Asus M4A89GTD PRO DDR3
CPU: AMD X6 1055T 2.8@3.5Ghz (1,325v)
Mem: 2x2 Gb DDR3 (Kingston KVR1333D3N9K2/4G) - Ganged Mode
CPU COOLING: Scythe Mugen 2 rev.B
GPU: Asus ENGTX470 607@780Mhz (stock aircooling & 1.025v)


Works both unganged and ganged.
Ganged mode is about 4% faster (10 minutes on a WU).
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Message boards : Number crunching : AMD, un-/ganged, what's faster at S@h ?

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