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FireWire Apr 25, 2013 09:31 PM
Damn it, Apple! (system freeze)
In the past, I rarely had to restart my machine (mid-2007 iMac with 6 GB RAM, 10.6.8). However, in the last months, OS X has been frustrating me a lot. It will sometime lock up and the only solution is to force reboot it with the power button. Suddenly, I can still move the mouse but everything else is locked, even the time in the upper corner. It usually happens when I'm getting really low on RAM (thanks to Safari, which tends to eat up over 1 GB of RAM after minutes...). I'm wondering why hasn't Apple came up with a way to avoid being starved for RAM to the point where everything is unusable.. A few times I was low on HD space so I thought the VM couldn't keep up, but it happened again even when I had plenty of space available (over 22 GB).
reader50 Apr 25, 2013 11:50 PM
Your drive may be developing issues. When you run out of RAM is when the system starts paging to disk. Open up Disk Utility, select the drive hardware icon on left (not the volume icon) and check the bottom of the DU window. You want the SMART status.

You might also use one of the more serious SMART utilities, like smartctl. Then copy and paste the detailed results here.
FireWire Apr 26, 2013 07:42 AM
I didn't think of that, but everything seems fine. Also, I noticed that when I'm running low on RAM, applications will become Not Available (in red in Activity monitor) and even when I free memory, they won't resume and have to be force-quitted.. Really disappointed in Apple...
reader50 Apr 26, 2013 01:47 PM
Wikipedia has a key for SMART codes.

I don't like #7 (Seek Error Rate) - your drive is missing the target a lot. An awful lot. First guess, this is the lockup reason.

Also 190/194 show the drive has gotten hot in the past. But Google's study of drive failure causes did not find a correlation between higher temps and failures. They also didn't go very far past the recommended temps.

195 (Hardware ECC Recovered) is high too. Since your Start/Stop Count and Power on Hours are low, I wouldn't expect so many error corrections.

What make / model is this drive? I'd replace it at this point. Or (if it's hard to replace) clone it to an external and boot off that for a month. To see if the lockups go away.
Spheric Harlot Apr 26, 2013 02:20 PM
^ I concur with the above.

You might also want to check what third-party device drivers you have installed, and whether they're compatible with the OS you're using.

I very much doubt that this problem has much to do with Apple, or is any cause for disappointment in them.
FireWire Apr 27, 2013 05:11 AM
Well, time to check my backup then! My drive is the 500 GB Seagate that came with my iMac (ST3500630AS Q). My computer did overheat a bit a few years ago because a thermal sensor had failed (the HD one, if I remember). The computer would get hotter until it shut down by itself. Apple replaced the sensor but it still got a bit hot so I installed smcFanControl to speed up the fans a bit, now it's fine. I was planning to replace my aging iMac with a new MBP this summer when the line get refreshed so I'll hope nothing breaks until then. Should I stop using it entirely? Can something get corrupted and get backuped by Time Machine? I'm doing fsck regularly and everything seems fine.

I tend to keep my system really clean so apart from printer and scanner drivers, which I keep up to date, I didn't install any drivers. I do have an aging USBOverdrive driver, however.

I was blaming Apple because I could see the available memory get lower and lower (up to a few MB) and the OS was doing nothing about it, until everything froze so I thought they didn't put any protection against this. But it's definitively their fault if Safari is crappy like this ;) I have to quit it many times a day because it's stealing all my RAM
Spheric Harlot Apr 27, 2013 05:25 AM
Lots of free RAM is a Bad Thing. The system is SUPPOSED to use all available RAM. That's what it's there for. Free RAM is a wasted resource that could better be used to make your computer faster and more responsive.
FireWire Apr 27, 2013 06:12 AM
Well the slow scrolling, tab switching and general computer lag caused by Safari says otherwise ;) An app monopolizing 1-2 GB of RAM, especially a mere browser, is not a good thing. Even iMovie and Photoshop are not that greedy... Maybe that's a good thing that the system uses all the memory for better operation, but when all the memory is stolen from a single app, that's another story...
Spheric Harlot Apr 27, 2013 06:52 AM
No. That is not a problem as such.

It only becomes a problem when the system needs to start swapping out to disk. And if you have less RAM than a single app needs, that means swapping out while you're just trying to use that single app.

That is not the case is you've got 6GB of RAM, and Safari is using 2 GB. If you're seeing swapping then, it cannot be blamed just on Safari.

In any case, your freezes and lock-ups are very unlikely to have anything to do with it.
FireWire Apr 27, 2013 07:27 AM
This is a typical Activity Monitor screenshot (which I originally posted in this thread) :
Spheric Harlot Apr 27, 2013 09:00 AM
That actually looks totally relaxed - for the moment.

The only thing out of the ordinary is the page-outs: That's a rather large number and would indicate that you need more RAM for how you're using the computer.

That should give you the spinning wheel, for sure, but it should not lock up the time, unless your machine is actually *hanging* — such as when it's paging to disk, but the disk isn't responding.
FireWire May 5, 2013 11:13 AM
So, about that hard drive, is it safe to continue using it (with a good backup) or the problem may get backed up and corrupt the backup also?
P May 5, 2013 01:17 PM
Quote, Originally Posted by FireWire (Post 4229196)
So, about that hard drive, is it safe to continue using it (with a good backup) or the problem may get backed up and corrupt the backup also?
The second. A suspect hard drive should be treated as toxic waste.
FireWire May 6, 2013 01:04 AM
Argh.. that's the internal HD of my iMac and I plan to buy a MBP this summer.. I don't really want to invest in it.. I guess booting from an external USB2 drive is too slow for daily operation?
P May 6, 2013 04:11 AM
I would consider it too slow. You'd be dependent on having lots of free RAM to act as disk cache to make it bearable.

You might consider a tiny SSD. You can find 60-80 GB SSDs for under $50 - just put the OS on it and everything else on the external drive.
FireWire May 6, 2013 06:35 PM
OK so I'll buy an SSD. I considered doing this in the past so I read a bit on the subject, but just to be sure:

- SATA III drives will work fine on my SATA II system off the shelf, without any special wire?
- Samsung 840 seems a recommanded buy?
- I will need a 2.5 to 3.5 adapter (any will do?)
- I will need to manually enable TRIM support (is it automatic now in ML? Is it a major hack?)
OreoCookie May 6, 2013 08:30 PM
Quote, Originally Posted by FireWire (Post 4229358)
- SATA III drives will work fine on my SATA II system off the shelf, without any special wire?
Yes, it will just work.
Quote, Originally Posted by FireWire (Post 4229358)
- Samsung 840 seems a recommanded buy?
Yes, that's the top recommendation these days. Next up, I would recommend Intel's 330/335 series (which is better value than the faster 520 series).
Quote, Originally Posted by FireWire (Post 4229358)
- I will need a 2.5 to 3.5 adapter (any will do?)
Yes, you'll need an adapter.
Quote, Originally Posted by FireWire (Post 4229358)
- I will need to manually enable TRIM support (is it automatic now in ML? Is it a major hack?)
I wouldn't change anything, leave it as it is.
FireWire May 6, 2013 10:45 PM
Great! Thank you everyone!
P May 7, 2013 03:51 AM
Note that the 2.5" to 3.5" adapter (which is just a metal bracket) is included with most end-user SSDs. Sometimes there is an OEM version without the bracket, but most SSDs do include it.

With your old SATA connection, the exact drive you pick is not important for performance reasons. As an alternative to the Samsung 840, you might find am 830 or 470 for less (note that Apple still uses the 830 or a Sandforce variant), and similar with other brands.
FireWire May 7, 2013 04:00 AM
that's good to know! I read on some forums that users said theirs came with the bracket but I didn't think it was common practice. I will look into a lower-end model then, if it doesn't matter much. I plan to ditch this computer in a few months anyway and will probably give it to a family member who will use it lightly. Thank you very much!

As I was getting more and more freezes, I decided to buy an external HD to boot from while I select my SSD solution. I installed ML and for now I find the speed quite acceptable! For some reasons it's even faster to browse files from this drive than from the internal! I did a clean install and I'm copying files manually since I was due for some spring cleaning after having this computer for 6 years!
CharlesS May 7, 2013 06:00 PM
Quote, Originally Posted by FireWire (Post 4229358)
- Samsung 840 seems a recommanded buy?
Samsung 840 Pro, yes; Samsung 840, no. The regular 840 model is a TLC drive, as opposed to most SSDs on the market which are MLC. TLC drives pack the data more tightly than MLC drives, allowing larger capacities at cheaper prices. However, the tradeoff is decreased longevity (about 1/3 the P/E cycles of an MLC drive, according to what I've read). TLC is also slightly slower than MLC, not that that matters so much. Eventually, TLC drives will probably take over the market, because they're cheap, and the almighty dollar is king. For now, TLC hasn't been on the market long enough for me to be comfortable trusting my data to it, personally.

If you want something cheaper than the 840 Pro, go with Crucial instead. They may not be as fast as Samsung, but they're so much faster than HDDs that you are unlikely to tell the difference, their reliability is rock-solid, and their support is top notch.
FireWire May 8, 2013 03:27 AM
D'oh! I just bought a regular 840. Anyway it's just temporary as I'll buy a new computer very soon and my current iMac will probably collect dust or be used by someone with very light needs.
OreoCookie May 8, 2013 08:44 PM
Quote, Originally Posted by FireWire (Post 4229631)
D'oh! I just bought a regular 840. Anyway it's just temporary as I'll buy a new computer very soon and my current iMac will probably collect dust or be used by someone with very light needs.
Don't worry, in most respects, your iMac limits the performance of the SSD anyway. (Yes, modern SSDs can transmit more data than the old SATA interfaces can handle! ;)) Most of the performance benefits come from the order-of-magnitude improvement of random reads and writes, and any modern SSD will run circles around your old hard drive.
FireWire May 11, 2013 04:09 AM
OK, I received my special tools today and I proceeded to install the new HD. Everything went fine until I had to install the provided bracket. There's a special part that we need to swap from the original HD to the bracket. (iMac Intel 24" EMC 2134 and 2211 Hard Drive Replacement - Page 3 - iFixit step 23 and 24). It appears the holes are not exactly the same size as I had to apply a great amount of force to screw the pins in place.. so much that my screwdriver broke (note to self: buy the premium part when available from ifixit next time). I could not longer finish the installatio and as I needed a computer, I improvized something to install the SSD anyway. I made a kind of bridge from cardboard and double-sided tape so the drive is secure. As this is a desktop computer, it will not move so it should break anything inside. My question is: can the cardboard catch fire of something because of the heat inside the computer? Can I leave it that way forever or it would be best to complete the install properly once I acquire new screwdriver?
Spheric Harlot May 11, 2013 04:37 AM
I would fix it up.

Nothing like moving the machine around when rearranging furniture or switching to a new machine, and then remembering that there's a provisional kludge solution in there that should have been looked at before you did that.
FireWire May 28, 2013 03:33 AM
I finally got a new screwdriver and opened my iMac up. I put the SSD on the proper bracket but when I went to put it back, the SATA and power connector wouldn't align.. Apple didn't see fit to include a few millimeters of leeway and the bracket maker put the holes centered so I had to unscrew everything and hold the SSD in place with good old double-sided tape, which is about the same kludge I had originally, only this time with the official bracket instead of cardboard. Was not happy about this but it wasn't so bad.

Note if you plan to do the same thing in the future: you will have to put your SSD and bracket face down for the SATA connector to be on the correct side.

The install looks complicated but it's really simple in reality. The part that got me the most nervous was not getting fingerprints on the inside of the glass.. To save time, I didn't unplug the LCD and just held it on its side with a box on my table. Be warned that you will have to exert great force to remove the bracket that is holding the original HD. The rest is really simple, as you just have a bunch of screws to remove and 3 wires to unplug. Don't hesitate to perform this upgrade if you have <150$ to spare and want a faster iMac! Don't be afraid to do it yourself.

Upgrading from 10.6.8 to Mountain Lion helped with the speed a lot! (I first installed ML on a USB2 external HD before I got my SSD so I know it's not just because of the new HD). Things are snappier and I have yet to have a single page-out while I used to have >10 GB of page outs before... Safari is much more responsive also. A 20$ well-spent!
OreoCookie May 28, 2013 09:09 AM
Even if you have page-outs now, you will notice them much less, because you have about ~10x the throughput and ~100x shorter access times.
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