Another 7970 question..

[deeja]

Hi,
I've been tasked to build a dedicated password cracking system for work but unfortunately I've not been given very much budget budget

Fortunately power costs, air conditioning, space and looks are not an issue for my solution.

After reading around on the forums I've decided to build an open air system (something like this) using risers and four 7970 cards.

I intend to use an existing motherboard, RAM, CPU etc so no cost their.

I've also got access to loads of standard power supplies - has anyone had any luck in using an Add2PSU to link them together? That would save me from buying a high power one.

As I'm not going to be putting the cards into a case, I guess it doesn't matter if they are reference models or not?

If that's the case, I've got quite a few 7970 cards as an option for me ranging from £200 - £400 (link to dabs).

Will I have any problems going for the cheap MSI AMD Radeon 7970 1050MHz 3GB cards for £244 rather than a much more expensive one, such as the 1100MHz Asus for £359?

Thanks for any advice.
D

[mastercracker]

You don't need to use Add2PSU. You have to either short 2 pins from the 20/24 pins connector (or use some custom designed connector) so that if you turn the PSU switch to on, it does turn on. You just have to make sure that the PSUs that are not linked to the motherboard are switch to on first (before turning on the computer). I use the round part of a paper clip to short my PSUs and put electrical tape over it. It's been working like that for 2 years without problems.

I am running 3 x 6970 from MSI and they are fine so I would not hesitate to pick the 7970 from them. Go cheap and buy more of them.

[deeja]

Thanks for the reply, I'm going to order the cards this week and start building the case tomorrow.

With respect to the riser cables, I presume I am best using ones with the additional power connector for the 7970 cards (like these)?
I'll post some picks and stats once it's working!
Regards
D

You don't need to use Add2PSU. You have to either short 2 pins from the 20/24 pins connector (or use some custom designed connector) so that if you turn the PSU switch to on, it does turn on. You just have to make sure that the PSUs that are not linked to the motherboard are switch to on first (before turning on the computer). I use the round part of a paper clip to short my PSUs and put electrical tape over it. It's been working like that for 2 years without problems.

I am running 3 x 6970 from MSI and they are fine so I would not hesitate to pick the 7970 from them. Go cheap and buy more of them.

[mastercracker]

In theory, the riser with the molex is better. I have not used one yet so I don't know if they are really effective.

[deeja]

As I'm having trouble sourcing 4x7970s or 2x7990s in the UK at a reasonable price, it looks like I'm going to order four 280x cards (which are also short in supply!).

I was thinking of either the Asus R9 280x 1000MHz or the XFX Radeon R9 280X 1080MHz. Has anyone had any bad experiences with these particular cards?

Cheers
D

[radix]

You really shouldn't use risers. Do it right the first time so you don't have headaches down the road.

Also, stay away from the x2xx series.

[deeja]

I finally got my system built using 290x cards.
Its all working like a dream, using od6config and an ADD2PSU card to link up multiple power supplies. I'm currently only using 2 x cards without risers and may buy a few more when I've got the funds!
D

[ati6990]

"I've not been given very much budget" "using risers" " Add2PSU to link them together"
uhh sure your system is working now ? for the money of 290x you can buy 4 x 6990 on ebay in god condition.

[deeja]

Unfortunately ebay is not an 'approved supplier' and I couldn't be bothered with the hassle I'd have to go through with our finance dept - and if I get any issues (or break them) I can send them back!

The box is working fine - I was going to build an open air system, but found a massive case in the back of a store room which has loads of fans and with a bit of jig saw action holds my two power supplies with room for a third. The cards are keeping pretty cool and I've got room on the board to fit a third, so I'm going to try and get some more cash approved...

For under £800 I'm pretty pleased with how its worked out and the speeds I'm getting.