Octofire?
#1
Hey all,

Having been bitten by this bug I've now finished strapping together my rig for light gaming and heavy hash cracking, comprising of:

5960x (@ 4.5ghz)
16gb DDR4 @ 3000Mhz
Asus Rampage V Xtreme
2 x 295x2's in Quadfire
4 x Samsung 120gb EVO SSD's in Raid0 (Not strictly necessary but as the drives are encrypted via AES-Twofish-Serpent it helps maintain speed)
Corsair 1500 Watt PSU

It got me thinking. The Two Radeon's don't cope so well with the loads of Hashcat, the reference AIO coolers are inadequate for the purpose and I will require custom watercooling loops in order to keep them cool during the summer. One of the benefits of this will be freeing up two PCIE Slots.

In my quest for ever increasing levels of power, Is there anything stopping me (apart from the obvious power and cooling overheads) from jamming in another pair of 295x2's? I understand they won't ever function as an 8-Way Crossfire for the majority of tasks on a PC, but as I understand Hashcat should have no problems utilizing all 4 (well, 8 I guess) GPU's?

Anyone care to comment?
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#2
Crossfire is a technology for rendering graphics in games, it has nothing to do with OpenCL computations.
Oclhashcat can and will utilize all available GPUs, easily.
And the only thing that may stop you from adding two more two-headed amd gpus are space constraints.
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#3
i've got the older HD 5970 ( 4 cards) in a single tower. OclHashcat uses all 8 gpus without issues.

the issues i struggle with are cooling and power
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#4
Power hasnt been a problem so far.

Heat however, is absolutely ridiculous. It turns a room from cool to uncomfortably warm in about half an hour. Im considering building some sort of modular rig to some radiators situated outside. With Australian Summer round the corner I don't want to mitigate half my A/C with graphics cards!
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#5
Well all 4 295x2's are now obtained, and currently waiting on an Asus X99e-WS for them as the Rampage V Xtreme wouldn't boot with them unfortunately - though I think this could be UEFI related. Either way the WS should be more suitable for this purpose anyway. It's all going into a 900D with a custom loop comprising of 4 EK 295x2 Blocks + Evo block for the 5960 with 1 x 480mm and 3 x 240mm radiators - though this may not be enough. And finally all powered by dual AXi1500's.
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#6
Keep us posted on how these radiators perform. From what I have been reading, you need roughly one radiator (usually with a 120 mm fan) per GPU. Since you have 240 mm radiators, you can might be able to cool better and cover 2 GPUs (1 card) with them. However, I think also that the 295x2 are notorious to produce lots of heat so I am curious to see the outcome.
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#7
Frustration unfortunately.

I cannot get anything more than 2 X 295x2's to get past POST. I get a several second delay on Qcode 79 - CSM Initialization and then a reboot at code 95 - PCI Bus Request Resources

Anyone who's run 4 x 2GPU Cards care to offer any suggestions?
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#8
did you enable above 4G decoding?
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#9
Start digging the problem:
- I suppose you updated the BIOS to the latest
- tune CPU and BIOS in safe mode, no overclocking, low RAM settings
- turn off every BIOS Optimization tool
- reduce your configuration to a known working status
- make sure all four graphic cards are fine; throw out all but one graphic card, test it, change to the next one
- same with RAM
- same with PSU
- increase number of graphic cards

From what i can see here you might have a power problem. By adding two more cards on the PCIE bus, 120 additional Watts have to be provided. Since each Mainboards mixes this power in its own way from +3.3V/+5V/+12V you might kick over the limit on one of these lines, esp. with overclocked CPU and RAM.

Good luck!
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#10
(01-18-2015, 11:54 AM)epixoip Wrote: did you enable above 4G decoding?

ThankyouThankyouThankyouThankyou epixoip, and thanks Flomac!

Now to navigate the nightmare that is trying to get them to all detect under Windows 8.1 Sad
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