OK just spent 45 minutes writing a reply on a Nexus 7 and the browser / forum lost it.
Anyway this may have been done to death, but I've got a question. What is going on with people building GPU mining rigs?
Is it the altruism - helping maintain the distributed safety of the network?
Is it the sheer tech geek fun factor - making mad machines for a laugh?
Is it for 'alternative' uses - from nice good Bitcoin mining to password bruteforcing / rainbow table / spook type stuff?
Is it because something has *fundamentally changed* to make GPU mining worthwhile recently???
OK, I'll front up - I've been around a while but was pretty much out of the picture in 2013 as I lost everything - health, job, family, home, assets, the whole shooting match. But this ain't a catfish sob story. This is my first return to the forum and for good reason...
As a few old timers will remember, I made a fair few insane home-made mining rigs, starting with lethal wooden contraptions with a couple of GPUs, onto bigger aluminium multi-GPUs-on-risers frames, and then to my silly 'shelf rigs' with three logic boards on each, all three with 4 overclocked GPUs on risers. I built a couple of those until the 1800W+ power consumption 24/7 at UK residential electricity rates, along with the insane noise and heat, really annoyed my girlfriend (we lasted 18 years, and Bitcoin was not the reason for it all ending...).
Actually, the whole big GPU rig paradigm started making no economic sense back then in 2012. I was barely breaking even, and that was ignoring the cost of dying equipment. I didn't over clock to insane levels (I underclocked RAM and over clocked core, plus volt tweaks as many others at the time) but 24/7 heavy lifting eventually ate Radeons and PSUs.
So I moved onto FPGAs, and even though our email styles (i.e. the owner and me!) didn't get on that well, I stuck with Ztex kit as I thought the quality was superb, and submitted a Mac OS X build for his then driver suite. I ended up with a few variations on 20 to 25 unit boards, all with crazy lights etc. and entertained at least a few on the 'show us your mining rigs' thread
Sadly, all the photos are hosted on my servers, and having lost my home and the static IP the servers lived on, you'll only find the text on the threads since I've no way of re-hosting the servers until I get a new place of my own and some new money...
Even so, commercial concerns and ASICs pushed difficulty to new heights, so the private miner really couldn't make even 'hobbyist' money without very large capital investments.
So what has changed? Yes, I'm aware of the large price rise in the BTC - and it's surprised me even though I'm fully aware of the deflationary econometric paradigm. But the ASIC-led difficulty must have made mining profitability almost pointless for anything other than those right in the inner circle, or those making a commercial investment (and a big one).
Can anyone clue me up?
Anyway, another reason the catfish is back. Around a year ago, when the FPGAs were barely breaking even, I ordered one BFL ASIC (a small Jalapeño) with money I really didn't have. Well, that year passed, and I've read enough about BFL, so along with the other heavy events of 2013, I wrote that particular 'investment' off long ago.
Well I received an import tax demand last week - something from the USA. I haven't bought anything for a very long time. Turns out it was my BFL Jalapeño.... of course BFL are now selling 600TH devices so my little box is already well out of date, so I'll have to work out whether power consumption / likely income is worth my while. And I've also read the horror stories of non-USA-120V power supplies for these units so will be using a proper earthed UK PSU before firing them up...
So the catfish is back Bitcoin mining! Woo hoo
But if anyone could clue me up as to why the hell anyone is still building GPU rigs, I'd be very interested. Are today's GPUs as fast as ASICs? Surely that's mad? And they surely still run hot and eat power?
All I know is that I'm better off selling my 2011 Casascius error-print physical bitcoins somehow... only three were ever made with the prefix 1Pi so any mathematical obsessives out there may be interested in rare coins!!! (sorry, wasn't meaning a sales pitch, I've got all three of them).
Anyway apologies for the massive off-topic outburst - first time back for the catfish
As to the OP's question - the largest number of GPUs I managed to run from a single logic board was 5. This logic board has 7 PCIe slots, and I was using mostly x16->x1 risers with a couple of x16->x16 risers. This is in the old days - cards were 5850s and 6950s, flashed, OCd/UCd as necessary, average performance 380-420MH per card. I needed two PSUs for that particular rig.
And the sheer unpredictable behaviour of the 5-GPU rig led me to my standard design, which used cheap 4-slot (1x16, 3x1) logic boards, 4 GPUs per logic board, as a modular design. Reliable and the odd crash (I used a Linux build, scripted and posted here IIRC) only took out one module than bringing down a huge rig with loads of GPUs.
IIRC there was a monster project with a special server logic board that aimed for 8 top-end GPUs on the one board. Never found out if that actually ended up working or not - don't think the BIOS manufacturers ever expected anyone pulling 60W through *every* PCIe bus (even if the PCIe power cabling should have supplied the majority of the power)....
Welcome back, Sorry to hear of your misfortune. Other alternative coins have came about that use a different proof of work algorithm, scrypt. A scrypt asic or fpga has yet to be developed, so the gpus are making a comeback. (It also adds cool points to brute force a 12 digit windows password in 3hrs.)
The 8 gpu setup never materialized I have seen the board, but never heard of one working. The pcie risers now use a connector for external power not drawn from the motherboard(when needed) From what I read most people use 5 gpus per motherboard.
