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Author Topic: Importance of GPU RAM for Litecoin Mining  (Read 14817 times)
W-M
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April 02, 2013, 10:02:59 PM
 #1

Hello there, everyone,

I have lately been looking into mining. I am new, and right now am deciding if/what hardware I want to buy. Mining Litecoin seems very lucrative at the moment(in comparison with BTC at least) because of the current difficulty and of course the near future when many people will use their ASICs on the Bitcoin network.
 On the internet I've seen some interesting GPUs for sale, and of course each model has a different average hashing rate.

However, some models also have variations with a different amount of RAM installed, e.g. both a 1GB version and a 2GB version. This brings me to my question:
Does the difference in on-board RAM change the Litecoin(Scrypt) hashing rate of a card much?

Thank you,

~W-M

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April 03, 2013, 11:12:37 PM
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I haven't found an answer yet. Is there anyone out here?

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April 03, 2013, 11:16:08 PM
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I wouldn't think that the increased RAM would cause any difference in hashing speed.

I think the bottleneck is the memory speed / engine speed.

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April 03, 2013, 11:24:13 PM
 #4

I dont mean to thread-jack but I have a similar question...

Does litecoin mining use more system ram or GPU ram? I know scrypt is very memory intensive but which memory does it use?


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April 03, 2013, 11:29:02 PM
 #5

I dont mean to thread-jack but I have a similar question...

Does litecoin mining use more system ram or GPU ram? I know scrypt is very memory intensive but which memory does it use?


The way I understand it, it uses both, however 2 Gb RAM on the mobo is all I've ever needed for any rig I've built (LTC or BTC.)

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April 04, 2013, 12:24:24 AM
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Also... I meant to add that because a rig with 8 GPU cores (8Gb total Video memory) hashes at the same speed with 2Gb system RAM or 8Gb system RAM, that it uses the video card's memory mostly.

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April 04, 2013, 12:27:54 AM
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You may get better results if you post in Alternate Currencies Smiley

Either way, from what I understand a higher memory clock is much more important than the actual amount of RAM on the card--1GB should be plenty. If you are talking about a 7xxx series above a 77xx then you want to be looking at getting a 0.57-0.6 ratio between core/memory.

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April 04, 2013, 02:01:56 AM
 #8

I dont mean to thread-jack but I have a similar question...

Does litecoin mining use more system ram or GPU ram? I know scrypt is very memory intensive but which memory does it use?



Depends on the software used to mine.
Reaper use the system RAM for mining, while cgminer is using GPU RAM.

Ex:
4 x 7970 are OK with 2GB RAM if using cgminer, but for reaper you will need around 8GB.
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April 09, 2013, 11:27:51 PM
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Still not sure if this question has been answered. Can a 6GB card outperform a 3GB card if core, mem and voltage are identical? If so, by how much?
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April 09, 2013, 11:53:22 PM
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Still not sure if this question has been answered. Can a 6GB card outperform a 3GB card if core, mem and voltage are identical? If so, by how much?

a 7990 with 6 gig is double the speed of a 7970 with 3 GIG (also 1 GPU instead of 2  Grin) bad exemple.

2 gig 7870 or 1 gig 7870 is a better question, don't know the answer
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April 09, 2013, 11:57:50 PM
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RAM isnt used to full capacity on 7xxx models. What is important however is bus speed. Which is the reason (most likely) why the Tahiti LE doesn't compete with Tahiti shader for shader.
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April 10, 2013, 12:52:00 AM
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From the Scrypt site http://hackage.haskell.org/packages/archive/scrypt/0.3.2/doc/html/Crypto-Scrypt.html

Quote
Parameters to the scrypt function

Scrypt takes three tuning parameters: N, r and p. They affect running time and memory usage:

Memory usage is approximately 128*r*N bytes. Note that the scryptParams function takes log_2(N) as a parameter. As an example, the defaultParams

   log_2(N) = 14, r = 8 and p = 1

lead to scrypt using 128 * 8 * 2^14 = 16M bytes of memory.

Running time is proportional to all of N, r and p. Since it's influence on memory usage is small, p can be used to independently tune the running time.


From: http://cryptocur.com/litecoin/


Quote
With the scrypt parameters used in litecoin’s implementation (N = 1024; p = 1; r = 1), each thread needs about 64-128 KB depending on the lookup_gap and thread_concurrency settings when mining with a GPU. This makes litecoin actually ideal to mine with a GPU, GPUs have very fast memory (bandwidths going into hundreds of GB/s) and generally 128-512 KB RAM per stream processor.
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April 10, 2013, 01:36:08 AM
 #13

Ok, here is a concrete example/problem.

3 Sapphire 7970s:

$410
http://www.superbiiz.com/detail.php?name=AT-H7970CB
Mfr Part Number: 11197-03-40G
Engine Clock: 950 MHz
Boost Clock: 1000 MHz
Video Memory: 3GB GDDR5
Memory Clock: 5700 / 5800(Boost) MHz Effective
Max Resolution: 4096 x 2160
Connectors: DVI-I, DVI-D, HDMI, DisplayPort
Dimensions (WxLxH): 120.0 x 280.0 x 40.0 mm

$436
http://www.superbiiz.com/detail.php?name=AT-7970GHZ
Mfr Part Number: 11197-12-40G
Engine Clock: 1000 MHz
Boost Clock: 1050 MHz
Video Memory: 3GB GDDR5
Memory Clock: 6000 MHz Effective
Max Resolution: 2560 x 1600
Connectors: DVI-I, DVI-D, HDMI, DisplayPort
Dimensions (WxLxH): 135.0 x 285.0 x 45.0 mm

$584
http://www.superbiiz.com/detail.php?name=AT-7970_6G
Mfr Part Number: 11197-05-40G
Engine Clock: 1000 MHz
Boost Clock: 1050 MHz
Video Memory: 6GB GDDR5
Memory Clock: 6000 MHz Effective
Max Resolution: 4096 x 2160
Connectors: DVI-I, DVI-D, HDMI, 2x Mini DisplayPort
Dimensions (WxLxH): 115.0 x 275.0 x 52.0 mm

I'm assuming the $410 one is the best choice, anyone one else have thoughts on the matter?
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