Bitcoin Forum

I just got a new iMac at work (I'm a PC/linux guy, but my boss is a Mac guy). It has a ATI 6970, which is one of the best video cards for bitcoin mining today. So I figure I'll download Diablo miner and set it up to run with default settings. Apparently Open CL doesn't work very well on a Mac, so I was only mining at about 1/4 the rate that the 6970 would get in a PC, but still figured it would be worth it to run it over the weekend.

So I come back on Monday, and the computer is froze. I restart, and I'm getting visual artifacts on the screen, and it freezes, usually at the login screen, sometimes it logs in, only to have more video artifacts, and freezes shortly after. I'm pretty sure I fried the video card. I'm assuming that the iMac must have really bad cooling on the video card, and it overheated. Aren't there any safety features to shut down the computer if the hardware is getting dangerously hot?

I load in safe mode, and delete everything related to bitcoin or the diablo miner, and call the company's tech guy complaining my New iMac is acting up, acting like I have no idea why it would do that.

Overheating happens, but usually the motherboard powers it down before anything like that happens...

That's a 6970_M_ (high end mobile part) in a very restricted-airflow case.  I would heartily second your recommendation of NOT mining with one of these.

would you leave a stove on, unattended? same thing with computers. ;)

Do you have Applecare? :P

Apple iMacs are known for video chip heat issues.  The design is wonderful looking (and I own one) but it is a lot of computer with a small set of fans.  You can run it hard, and just playing games heats my whole machine up.  I would not mine on a iMac or even visit a site that mines in the browser for long (minutes or even an hour should be ok, all night long no). 

You've got to remember, laptops have terrible airflow. The 6970 is a powerful card and you've got to take into consideration that while playing a game, this card might top out at %50 gpu load and the rest of the time you're playing usually hovers around %20 (this is a dx11 game i'm talking about, visually demanding games). While bitcoin mining, your gpu is running under a load 5X the size of running a dx11 game at max. This is a fine way to destroy any laptop.

iMacs are the one piece desktop computer line with the screen built in, not technically a laptop but obviously very similar.

and don't buy anything from Apple or other exploiting companies /slavers for rest purposes.

Strange. the iMac i overtook in my university (guest account, logged on in background) still mines.
All day, all night. and due to multi-user-login it's seems still usable for the other students (otherwise they would had shuted it off already)

Those machines are designed for aesthetics not for power crunching

the cooling systems are not designed at all for that kind of use
 

it is quite possible the gpu overheated and was permanently damaged.

best thing to do is not tell anyone what you did. Delete all signs of bitcoin off of the machine and then walk into your boss's office wit a puzzled look on your face "gee boss I dunno what happened"


Theres a good chance Apple care will fix the repair but they may try to weasel out of it if they knew you were bit mining with it.

I am not saying it will fail, but it has a much higher chance of failing running 100% GPU load on an iMac for a long time.  You may not have any problem.  You also may be CPU mining which still puts heat stress on the machine, but it may not be as bad.

Would there be any basis for that though if there was no evidence of overclocking or warranty voiding modification? Just running a taxing program on a computer and having it die seems more like a design/manufacturing flaw. Apple seems to have a history of that happening with certain models, e.g. the G4 cube. I think they believe the noise of a fan detracts from the zen experience of using their computers, or something along those lines.

Chances are if you send it in to Apple, they'll see the artifacts and automatically assume overclocking. They'll most likely do some tests on it and find that the card is running perfectly fine temps and assume you were grinding the shit out of the card somehow.

I'm not saying they won't replace it for you as I've never dealt with Apple. I'm just saying that it's very likely they will know that it wasn't faulty hardware to begin with.

A Mac not mining bitcoin's well/efficiently? Color me surprised.

Also what twitcoins said: Mobile is quite different from the "real" model. Advertising trick, and a good one. I don't know how many friends think they have a good graphics card in a laptop because they don't know the difference between a XXXXM and a XXXX.

Yeah, I have a friend who gpu mined on his imac while we were getting started mining. About two days later I come to his house and point out a blue vertical line on the same computer's monitor. We immediately stopped, but the damage had been done. Not worth it for the ~35 Mhash/s.

Wait for sonnet to release their thunderbolt to pci express enclosure (http://www.sonnettech.com/news/nab2011/ (http://www.sonnettech.com/news/nab2011/)). Then with 2x thunderbolt ports you can daisy chain up to 12 graphics cards to one iMac (24 gpus with 6970's :).

I have the cheapest new iMac with a 6750 card.  When I first ran a miner on it it got hot, that was a CPU miner.  Then I ran DiabloMiner which uses the GPU and it doesn't generate any extra heat.

I calculated how much money I was getting for the watts I was burning and turned the miner off.  But after the price of bitcoins went over $20 I have started running my iMac miner again.  After about a week of this I have not had any trouble.

I'm guessing that the iMac uses 200 watts, I could measure it but I haven't.  That's about $0.78/day added to my electric bill.  The iMac does 44 MHashes/second, with the latest difficulty change that's about $0.84/day added to my bitcoin wallet.  Now that I've done the calculation again I'm not going to run my iMac as a miner anymore.

The best reason to not mine on my iMac is that it doesn't make any money.

My other miner is a 2.4 GHash/second machine.

Sam

Have you seen the size of the 6970? There's no way that the desktop version would even fit inside the iMac, never mind be cooled properly. They shouldn't be allowed to fool people into thinking they're using decent GPUs when it's only the mobile version :(

Thunderbolt is apparently an external connection based on PCI-e, so no need to put the cards in the computer. Obviously power would be another issue though.

It was faulty hardware to begin with, though, that's the thing. It might not be everyday usage to run the thing at 100% GPU load, but that doesn't mean it's out-of-warranty usage (although overclocking would be).

In any case, I'd be very surprised if they didn't replace it without question - I've never had any major hassle with in-warranty servicing from Apple, and with the margins they make on their hardware, it's easier to just replace it and have a happy customer than waste the time arguing.

OK I just measured the power through my iMac with a 6750 chip in it.

iMac not mining:              72 watts.
iMac running DiabloMiner: 88 watts.

So turning mining on adds 16 watts!  Whereas mining on my 5850 adds about 150 watts.

The iMac is not using much power for the graphics card!

The the electricity to keep the iMac on all day mining is only $0.34.  Whereas the 44 MHash/second earns you $0.85.

So the iMac is still profitable as a miner.

Sam

5850 > 6750
your argument is invalid. It's like saying "derp imma use 6650 to mine, coz it use 50W!!"

Anyone have any idea if Lion will even come close to fixing this? Or is there going to be no change?

Yes it does indeed appear so.  Upgrading from SL to Lion has roughly doubled DiabloMiner.app's performance on my MacPro from an average of 140MH/s to 285MH/s with a Radeon HD5870. 

i'd extend this thread to not mine on any laptop based computer or laptop :P all in one boards in small enclosures are not made for 24/7 mining. Your just asking for trouble. unless you get your own cooling solutions going.

At least you got a half bitcoin!  Don't spend it all in one place!

You do realize that is a 6750M as MOBILE, as in a laptop chip. 6750M is not the same as a desktop 6750 (if there even is such a thing).

Hm.. If you bought an expensive car, should you not be able to drive it across America without it breaking down the first night?

Yet you accept that an iMac breaks down after one night of bitcoin mining ?

Sounds like poor engineering from Apple's part if you ask me. What's the point of having a powerful computer if it can't be run to the maximum? Would you buy a house with 8 rooms, where you could never use more than 5 of the rooms, and if you did, the house would fall apart?


I am sure there are legitimate uses of running the GPU's at full speed apart from bitcoin mining. But now everyone know to stay away from the iMac when mining.

What about suing Apple over this? Would it be less ridiculous than Apple suing MACARAJA (http://macaraja.com/macaraja_apple_en.php)?

Wow sorry to hear that but still kinda LOL.  :P

I mine with my iMac. It's got a 6750M as well. But I've notched up the fans with SMC Fan Control so the GPU temp doesn't go beyond 60 C.

old topic but question that i'm still trying to answer: how loud is your iMac while mining? thanks in advance. have a lovely day.

I'm guessing the fans would go all the way up. Hear what that sounds like by googling and downloading smcfancontrol which lets you set preferred fan speed settings from the menubar. Just create a setting where the fans are on full. I do that for mining on Mac Pros and they're pretty loud either way, but my MacBook Pro is fairly quiet even on full. Seeing as you have a mobile GPU it might not be too bad.

Don't steal from work.

A mac is a terrible, inefficient choice for mining of any kind. A purpose built PC can do it much better and allows for future expansion with more GPUs, or as a host system for future ASIC devices, diverting GPU power to Litecoin later on as GPU mining for Bitcoin is just about to get snuffed out by immensely superior hardware.

It's funny how i-devices are not designed such a way you could utilize their 100% potentional without damaging them. All at the cost of better looks and "usability".

Like a car that breaks a propshaft if you put your feet down, who would buy such a car? Somehow it seems to be acceptable in electronics.