Require a little help here.
#1
Hello all! Ive started studying password cracking since a couple of months and now I plan to build my first computer for gpu cracking.

So for the moment I will start building something with a budget.
I will get a mobo (150-200$) with 4x pci express slot. I will start with one graphic card and eventually add them until I get the 4x maximum.

Some things im wondering and would like to have you guys help:

How important is the cpu for gpu cracking? Should I get like a cheap dual core or a good quad core.

How much ram would I need and does the ram speed play a role.

If I have the 4x graphic card set on the mobo, would a 1000psu be sufficient or I will need at least two psu?

Should I get extra fan?

Any suggestion is appreciated, thanks
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#2
If you know you will only do gpu cracking a cheap dual core will be fine. RAM speed doesn't matter at all.

Power consumption obviously depends on the gpus you have.

The type of cooling you need depends on your case and your environment.
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#3
(01-26-2015, 01:27 AM)SolidSnake Wrote: How important is the cpu for gpu cracking? Should I get like a cheap dual core or a good quad core.

I would suggest going with a solid mid-range CPU, for two reasons. First, you likely will still do some CPU cracking. For example, straight wordlist attacks against fast hashes are faster on CPU than GPU, bcrypt is still faster on CPU, and scrypt with large memory requirements is impossible on GPU. Also not all algorithms have been implemented on GPU. Second, you will want a decent CPU for doing things like wordlist manipulation and potfile management.


(01-26-2015, 01:27 AM)SolidSnake Wrote: How much ram would I need and does the ram speed play a role.

You should have at least as much host RAM as video RAM. So if you have four GPUs with 4GB of vram each, then you should have at least 16GB of host RAM. RAM also helps when doing things such as wordlist manipulation. RAM is cheap, there's no reason to skimp out.


(01-26-2015, 01:27 AM)SolidSnake Wrote: If I have the 4x graphic card set on the mobo, would a 1000psu be sufficient or I will need at least two psu?

Depends on what GPU you buy, but no, in general a 1000W PSU would not be enough to power a quad-GPU system, nor would it likely have enough PCI-e power connectors for four GPUs.

You'll have to do the math once you select your GPUs, but there's really no reason not to go with the biggest and best PSU you can find. I'm quite partial to the EVGA 1600 T2 and Lepa G1600.

A good power supply is cheap insurance. If your PSU can't keep up with demand, you will find yourself buying not only a new PSU, but also likely a new motherboard as well.
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#4
(01-26-2015, 06:01 AM)epixoip Wrote:
(01-26-2015, 01:27 AM)SolidSnake Wrote: How important is the cpu for gpu cracking? Should I get like a cheap dual core or a good quad core.

I would suggest going with a solid mid-range CPU, for two reasons. First, you likely will still do some CPU cracking. For example, straight wordlist attacks against fast hashes are faster on CPU than GPU, bcrypt is still faster on CPU, and scrypt with large memory requirements is impossible on GPU. Also not all algorithms have been implemented on GPU. Second, you will want a decent CPU for doing things like wordlist manipulation and potfile management.


(01-26-2015, 01:27 AM)SolidSnake Wrote: How much ram would I need and does the ram speed play a role.

You should have at least as much host RAM as video RAM. So if you have four GPUs with 4GB of vram each, then you should have at least 16GB of host RAM. RAM also helps when doing things such as wordlist manipulation. RAM is cheap, there's no reason to skimp out.


(01-26-2015, 01:27 AM)SolidSnake Wrote: If I have the 4x graphic card set on the mobo, would a 1000psu be sufficient or I will need at least two psu?

Depends on what GPU you buy, but no, in general a 1000W PSU would not be enough to power a quad-GPU system, nor would it likely have enough PCI-e power connectors for four GPUs.

You'll have to do the math once you select your GPUs, but there's really no reason not to go with the biggest and best PSU you can find. I'm quite partial to the EVGA 1600 T2 and Lepa G1600.

A good power supply is cheap insurance. If your PSU can't keep up with demand, you will find yourself buying not only a new PSU, but also likely a new motherboard as well.

Hey thanks a lot for the reply, its very helpful!

Now im looking to start buying one or two graphic cards. Im looking for Radeon Hd 7970 or 7950, But im having a hard time finding reference cards!! Where can I purchase those ? I usually shop from newegg but they dont tell if its reference or not.

Please let me know, thanks again.
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#5
This post explains the difference between reference design and OEM design cards, and how to tell the difference: http://hashcat.net/forum/thread-3949-pos...l#pid22844

The 7970 & 7950 are last-gen cards from 2012 so yes, I imagine you would have a hard time finding some new. But you can likely find good used ones on eBay.
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#6
(01-29-2015, 06:23 AM)epixoip Wrote: This post explains the difference between reference design and OEM design cards, and how to tell the difference: http://hashcat.net/forum/thread-3949-pos...l#pid22844

The 7970 & 7950 are last-gen cards from 2012 so yes, I imagine you would have a hard time finding some new. But you can likely find good used ones on eBay.

Yes I have read your post about it already. Seems like getting used cards from Ebay is among the only solutions to get them. But the problem is that theres always a risk from getting used stuff from ebay and also will probably not even be able to find x4 of the same.

When you say "Always buy reference design cards. Period. " does it mean if I get non-reference design it might not work for password cracking or can overheat quickly and die?

Also what about getting 4x Nvidia GTX 750Ti. Do you think it can still make some decent cracking?

Is there any other non-reference cards that will work multi gpu that you can suggest to me?

Thanks thanks
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#7
You will absolutely have cooling problems with non-reference design GPUs, especially in a multi-GPU setup. In addition to cooling problems, yes, OEM design cards are of inferior quality. I have lots of horror stories from using OEM design cards. They are junk, do not waste your time and money buying them.

Buying used reference design GPUs -- especially GPUs still within their warranty period -- is very low risk. True story: most all of the GPUs we run in our data center were in fact purchased second-hand from eBay and mining forums. We've only lost one second-hand GPU in the last four years, and since it was still under warranty we just RMA'd it. Reference cards are over-engineered and very high quality.

750Ti is a great budget card. But you just went from top-of-the-line cards to budget card, so I'm kind of confused.
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#8
I'd say if you buy it just for playing around, cut down on the mobo and buy a cheaper one with two PCI-E slots. Put the saved money in a decent graaphic card like epixoip suggested and you still have room for another one later. Don't waste money and time with something like the 750Ti unless its lying around. It's already outdated since the GTX 960 just came out, which offers better performance, better price/value, a newer chip generation and reference design. Two GTX 960 cost less than one GTX 980, but should perform equivalent with Hashcat. So there you go, if you get yourself one of these you can upgrade later and still have very solid performance on your hand.
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#9
Here's one of the GTX980 reference cards( I think)
EVGA GeForce GTX980 Reference 4GB GDDR5 256BIT DUAL-LINK DVI-I 3 X DP HDMI SLI Ready Graphics Card

[Image: 105eghu.jpg]

It's say Nvidia on the board
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#10
Yes, that's a reference design card. But not because it says "nvidia" on the board, I believe most if not all say that.
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