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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > 20" iMac G5 (first generation) - S-L-O-W

20" iMac G5 (first generation) - S-L-O-W
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May 1, 2013, 10:11 AM
 
I picked up an iMac G5 from a friend last year, and have started using it as a backup computer in our office. It's an okay machine, but I've noticed that it is really freaking slow, particularly when browsing the Internet with more than a couple tabs open (I use TenFourFox).

Current config is 2GB RAM and a 500GB 7200RPM hard drive; I'm running Leopard.

Given how well Leopard generally performs on my Power Mac G4 with a Radeon 9700, I'm guessing the bottleneck is the GPU on the iMac. Is there anything I can do to make it suck less?
     
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May 1, 2013, 01:34 PM
 
I'd also flag the hard drive as a bottleneck. A modern drive will have at least 2x the transfer rate.

Regarding the GPU, all I'm thinking of is if you used a full retail Leopard DVD for the install, or a disk that came with another Mac. And may lack the iMac GPU drivers.
     
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May 1, 2013, 02:02 PM
 
It's a SATA drive, although I don't know what generation SATA - I'm guessing 1.5GBps?

As far as the Leopard install, I did use a retail DVD. This iMac shipped with Tiger (I do have the original disks for that). Is there something I can do to verify that it has the right video driver? I feel like a retard for asking that, but aside from the first unibody MBAs, I always just assumed that between the retail installer CDs/DVDs and Software Update, you were guaranteed to have the right drivers for all the hardware.
     
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May 1, 2013, 03:39 PM
 
I'm with Reader50 on this, I think it's the drive.

Try a (cheap) SSD. Not only is it faster than a (really old at this point) platter drive, it'll also boost memory pages to and from the drive.
     
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May 1, 2013, 03:55 PM
 
First, try to rule out any software problems. If you've got an external hard drive, start up from that and see if your browser isn't still running slow. With 2GB of RAM, it shouldn't be, but if so, the next step would be to run the Apple Hardware Test DVD. The extended test will take a while, so don't plan on using your computer for a half hour or so.

My guess is that it's probably nothing that reinstalling the OS won't solve. A GPU issue would give you display issues and might prevent the OS from booting, but I don't know if it could be a RAM problem - the hardware test would find that. Or I guess it could be the hard drive dying; I remember a few years ago my iMac G5 started slowing down before the HD bit the dust. Then last fall I had the GPU issues I just mentioned, and ended up replacing the logic board.
     
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May 1, 2013, 04:09 PM
 
OP reinstalled the OS, that was my first thought too. Digital bitrot.
     
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May 1, 2013, 04:44 PM
 
Oh yes, drive fill and fragmentation. If it was an update install from Tiger, and the drive has ever been past 90% full, your browser cache files could be scattered all over. Which would explain the slowness with multiple tabs open.

Go to a bigger, newer HD with a fresh OS install. Or an SSD if you're willing to pay the price. Or live within a 128 GB SSD.

Download the iDefrag demo and look over your fragmentation.
     
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May 1, 2013, 09:33 PM
 
I did a straight up format and fresh install. This was purchased used, so first thing I did was a format and reinstall of OS X.

I'm going to try an SSD, I think. I have OS X (10.4 and 10.5) on a FW HDD, so I'm going to boot off that and see how it performs. If it looks like everything is good, I'll just install an SSD.

I'm also going to see if I can nab a copy of ASD for this machine to put it through its paces...we'll see.
     
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May 2, 2013, 03:50 PM
 
How about upping the RAM to 4gigs?
     
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May 2, 2013, 04:17 PM
 
Disk Utility run off an external FW hard drive showed no issues. That said, I'll try an SSD and see how it goes. I tried using Safari off my external hard drive and loading Gmail, and it wouldn't load the interface. Not sure if that's because that copy of Safari is woefully out of date, though...

Also: what exactly is digital bitrot?

Originally Posted by jmiddel View Post
How about upping the RAM to 4gigs?
Can't - the first rev iMac can only take 2GB RAM between two full-size DDR DIMMs.
     
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May 2, 2013, 04:39 PM
 
Originally Posted by shifuimam View Post
Also: what exactly is digital bitrot?
Nothing technical. Just what I call the cause of machines that need a fresh OS install to fix issues.
     
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May 3, 2013, 04:24 AM
 
Note that the G5s were never particularly fast at branchy code such as general integer code - in particular Javascript. The main memory latency was very high, and the L2 cache in those first G5s was too small to hide it.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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May 3, 2013, 05:10 PM
 
Originally Posted by P View Post
Note that the G5s were never particularly fast at branchy code such as general integer code - in particular Javascript. The main memory latency was very high, and the L2 cache in those first G5s was too small to hide it.
Ah, that would probably explain the unresponsive script errors I always get at certain sites like the Huffington Post or Yahoo News pages. I've been told that the trend in web development over the last few years has been toward heavier use of Javascript and other front end content to minimize the processing load on the servers. And this is a 2GHz G5, so a slower one would probably crap out more quickly.
     
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May 3, 2013, 05:14 PM
 
Ehermagherd! I get those obnoxious script errors too! I didn't realize the specifics of the hardware could determine that kind of performance.

I've been using AdBlock to selectively block scripts for stuff I don't use (like Twitter integration). Unfortunately it's impossible to use most popular websites these days without JavaScript enabled, though.

Anyhow, I installed an SSD last night (my ghettoest mod ever, in which I just used Kapton tape to attach the 2.5" SSD to one of the iMac's hard drive brackets and supported it with the plastic packaging it came in), and I've definitely noticed an improvement in general performance. The old hard drive is coming up clean with fsck/Disk Utility, but it's been irritatingly slow when copying my data off it over USB 2.0, so I'm guessing it's on its last legs.

At least this thing is usable now! It was getting *really* bad.
     
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May 4, 2013, 08:49 AM
 
Wasn't aware the the javascriptification was getting bad enough that G5s are getting unusable, but yes, modern sites use a lot of it - often crosscompiled from something else. Maybe modern JIT compilers are simply unsuited to the G5 design, but that would imply that an early P4 would be almost as unusable. Later P4 models could use the bigger L2 and HT to hide it, maybe.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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May 4, 2013, 12:43 PM
 
It might also be that the CISC architecture can handle such demands more fluidly, too.

That being said, this stuff is all way over my head. I'm using TenFourFox 17, which is a G5-optimized build of Firefox 17. I'm going to try Opera, too.

In the meantime, I can keep using AdBlock Plus to prevent unnecessary scripts from running, so that does help. I think the hard drive was the biggest problem with this machine - I've been doing stuff with it since I did the SSD upgrade a couple nights ago, and it's running much more smoothly. I also have a really bad habit of keeping 10+ tabs open when browsing, and I doubt that helps at all since Firefox keeps all those tabs in RAM.

I have noticed, interestingly, since the SSD upgrade my CPU meter doesn't languish at >=50% utilization anymore. I'll keep using this for awhile and see how it goes...if it's terrible I may end up replacing it with my modded Power Mac G4, which is fantastic at handling pretty much everything except HD video.
     
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May 4, 2013, 02:05 PM
 
You may also want to experiment with the Energy Saver control panel and see if it makes a difference when you set the processor performance to Highest instead of Automatic. With mine, this sometimes helps with video playback, and I'm sure there are other uses that don't provide visual feedback. Just keep an eye on the CPU temperature; I'm not sure you'd want to constantly keep it on that setting.

Where I work, they still have a few old Pentium 4 machines. I sometimes get those same JavaScript errors, but sometimes the 3GHz P4s can barely handle sites I had no trouble accessing on a 1.8 GHz G5. Also, the CPU exhaust is hot enough to keep my fo coffee warm.
     
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May 4, 2013, 03:17 PM
 
++ on the Energy Saver tip below - that can make a real difference.

Originally Posted by shifuimam View Post
It might also be that the CISC architecture can handle such demands more fluidly, too.
That's the other way around actually, but any Intel chip since 1995 is quite RISCy internally with a translation engine to turn x86 instruction into RISCy so-called uops for execution.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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May 7, 2013, 09:51 PM
 
I'll try the processor performance bit too, if that's an option (can't remember offhand).

The GPU is definitely not the greatest - I installed an old PPC version of XScreenSaver, and all the OpenGL ones run like total crap. Ah well...I suppose it is a pretty old machine.

SSD was worth it, though.
     
   
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