Leopard running slow on your ageing Mac? Here’s how to speed it up: fewer colours (update: except Apple won’t let you)

Switch your display to speed up older Macs running LeopardTo cut to the chase: Leopard, besides switching off your firewall in the upgrade, also switches your display preferences for colours displayed from “thousands” – if that’s how you had it set – to “millions”.

Since that’s a difference which can suck up huge amounts of RAM, swap memory and CPU/GPU (“huge” being relative to the amount you have available), it’s a hidden change which isn’t very welcome. (For those who argue below that it “won’t make a difference” – System Profiler says that thousands of colours is 16-bit colour, and that millions is 32-bit colour. (Try it. Refresh System Profiler – Cmd-R – after you change the settings in the prefs. 32-bit must take extra GPU time and memory to process; it’s got to mean more data shunted around the system. It can’t be “no difference”.)
So, to speed up your machine: go to System Preferences, choose Displays -> Colours, and change the setting from “Millions” of colours to “Thousands”. Voila! Faster machine. Except see below – the change doesn’t stick for me.

And now, the backstory: since upgrading to Leopard – this on a 1.67GHz, 1GB RAM PowerBook (vintage March 2005) with 10GB or so of free disk space – I’d been puzzled by quite how slow it was. Switching between applications took ages; the windowserver application seemed to be taking a huge amount of CPU. Nothing happened fast.

And then after reading John Gruber’s notes about anti-aliasing, I thought I’d pay a visit to see whether my display was set to the right anti-aliasing setting.

It was. But what I also discovered was that Leopard, during the upgrade, had switched my display preference from thousands of colours to millions. (Strike another one up to the power of serendipity.)

I’m pretty confident that I had it on thousands before, because the difference to me between 8-bit colour and 12-bit colour (which I think, without checking, is the difference between thousands and millions) isn’t worth bothering with. I don’t do artwork on my machine. I’m not a photographer. I’d rather have fast and approximate with pictures than slow and precise. And I’ve made that change in the past to speed up my machine.

What I don’t understand is why Apple makes this change in the upgrade. It’s a guaranteed way to make your machine seem slower than it was before. Which isn’t what you’d want to do, is it?

The results for me: machine is faster; screensaver goes away quicker; switching between applications is faster. Visual penalty: undetectable. Try it and see. Obviously, if you’re disappointed, you’re entitled to a full refund of your five minutes spent here.

Update: OK, I’ve now done three logouts (one after yet another really annoying system total freeze) and the change hasn’t stuck. Every time I log in it’s back to millions. That’s either screwed up – which is bad – or a bad decision by Apple. Either way, grr. And these complete freezes are really trying my patience.


  1. Simple math:
    8 bit = 2^8 = 256 color palette.
    16 bit = 2^16 = 65536 color palette (or Thousands).
    32 bit = 2^32 = 4294967296 color palette, although actually I believe it uses 24 bit (16777216) for color information and 8 bits for levels of transparency (alpha channel).
    Your grasp of these extremely simple mathematical and computer concepts make me very doubtful that you can actually gain any speed by setting your machine to Thousands of colors. Regardless, I’ll give it a try since my Powerbook feels sluggish when switching apps ever since I installed Leopard.

    (just in case, the ^ symbols is being used to denote exponent).

  2. marcos,
    interface speed is subjective. having said that, reducing the color palette is a tried and true way of speeding up performance, particularly on hardware that was manufactured for earlier os’s. your mileage *will* vary but i have been supporting macs for years and i know that the basis of this advice is sound.

  3. No, it’s just placebo effect.

  4. Well, sugar, I’m going to try it anyway.

  5. hey charles,

    thanks for the tip. do you know any other suggestions to boost performances on vintage powerbooks? i’ve had this beast since 2004, and it’s running on 1.5 gb of ram just on tiger, but it’s still super chunky and slow because i’m a heavy user of adobe apps; i’d just like to know the best practices to still get the best out of my ppc machine before i’m pinned down to get a new intel machine.


  6. Charles

    Tuesday 4 December 2007 at 12:16 pm

    @alvin: other not-obvious tips include:
    -have very few files on your Desktop (for some reason this slows performance)
    -have your CPU on max, or whatever the setting is – see the Energy Saver preference
    -make sure you have lots of free disk space; at least 10% of the drive capacity. If you’ve got your music collection on your machine, it may take up a lot of space; you can easily move it to an external drive and point iTunes to it. (Note: you may lose smart lists which depend on when a song was played when iTunes re-indexes the – to it – “new” songs.) Ditto with movies and video files – iMovie and iDVD can take huge amounts of room without your realising it.
    -have few windows open
    -hide applications
    -quit applications you don’t need open
    -don’t use Java apps if you can avoid them, since they seem to be resource hogs.

  7. Your Powerbook is slower on Leopard because Apple made changes to the OS that optimize it for Intel processors and the result is less optimization for PPC. The best thing you can do for performance is double your memory which at 1GB is insufficient. Just keep activity monitor open and you will see that most often when things are dogging you have no free memory available. Even with 2GB I run into this more often with Leopard.

  8. Ugh. Lots of bad advice here.

    Running in thousands vs millions will reduce the amount of RAM needed to render windows. That’s all it will do. It won’t magically speed up your computer.

    If you’re short of RAM, then reducing your RAM requirements will indeed avoid virtual memory related slowdowns. But if you have adequate RAM to avoid swapping, then it won’t affect your performance at all. For the less technically inclined folks out there, this means that if you have a GB of RAM in your Mac, running in thousands of colors won’t help you at all.

    Also, the difference between thousands and millions is plainly visible to the naked eye. If you really can’t see the difference, you might have larger problems than a slow computer.

  9. Charles

    Tuesday 4 December 2007 at 4:36 pm

    @David: I can’t up the RAM – I’ve got the PBook “dead lower RAM slot” problem. Unfixed so far, because I need my machine for work.

    And you can’t avoid some RAM swapping. Activity Monitor shows that the swapfiles for some applications (such as browsers) runs to 1GB or more. Throwing RAM at the problem won’t solve it.

    @Chucky: If it reduces the amount of RAM needed to render windows, won’t it be able to render them faster? Less contention for RAM, and less data to move across the frontside bus (which, remember, is comparatively slow on this generation of PowerBook)? Less work for the GPU to do. Try it the other way: if I was doing it in 96-bit colour, wouldn’t it take more time to calculate precisely what colour each pixel should be as I moved windows around, or moved from one application to another and made a different window (=area of RAM) frontmost? Your argument implies it makes no difference to CPU/GPU load how many colours we work in. That can’t be.

    I don’t have adequate RAM to avoid swapping – nobody does. That’s why we all have huge swapfiles living on our hard drives. See Activity Monitor’s “virtual RAM” column. (See Apple’s info: http://docs.info.apple.com/article.html?artnum=107918). Activity Monitor thinks I have 53GB of VM, which is impressive, I think we can agree.

    As to the difference between thousands and millions – as I said, I’m not doing work on photos here. It might be visible to the naked eye, but the question is whether it makes any appreciable *difference* to the content of my work – which, since it tends to be about black text on a white background, gets answered with a “no” here.

  10. “I donít have adequate RAM to avoid swapping – nobody does. Thatís why we all have huge swapfiles living on our hard drives”

    Not quite the point here.

    If you’ve got a LOT of windows open, you can perhaps save yourself 25 – 50 MB of RAM by running in thousands vs millions. That can have a noticeable impact on your computing responsiveness if you’ve got a machine with 384mb or 512mb of RAM, given that the system sucks up a big chunk of that small pool of available RAM already. But if you’ve got a GB of RAM or more, saving 25 – 50 MB of RAM isn’t going to make a difference.

    “Your argument implies it makes no difference to CPU/GPU load how many colours we work in.”

    It makes no noticeable difference.


    I once had a girlfriend with an old iMac with 384mb of RAM who liked to run Word, Photoshop, and a browser with many open tabs all simultaneously. I shifted her to thousands of colors, since it made sense in her particular case. But I wouldn’t recommend it for most other folks who aren’t so horribly RAM constrained.

  11. Lots of bad comments. It DOES speed your machine to run Thousands vs Millions as there’s LESS DATA to move around the bus.

    It IS true that having less/no files on the Desktop will help speed because each icon is treated as a window (I think DaringFireball.net linked to a post about that). Each window has overhead.

    It’s a good idea to have the display icon in the menubar so you can change your color depth when working with photos.

    As someone mentioned, hiding apps vs minimizing and whatnot should help as the windowmanager memory used to display the windows should be released for other use. If your GPU is used to store any of that, it will help there too. This is from my knowledge and hasn’t been proven.

    Charles, have you tried nuking prefs and cache to get the setting to stick?

  12. I think Chucky is right to say that you save yourself “only” 25-50MB of RAM by switching from millions to thousands. (I did the numbers – 1280 pixels x 854, 16-bit colour works out to roughly 32MB.)

    Question is, how much can your GPU – not CPU – push through? And is the CPU involved in calculating pixel values?

  13. I’ve just upgraded to Leopard on my 1Ghz Powerbook and it’s painfully slow. It’s like in the bad old days with my windows laptop and XP. I thought those days were behind me!
    I’ve got 768 mb of RAM but I believe there is only one slot, and I’m told I can put a maximum of 1 gig of Ram in giving me a total of 1.256gig. Is this the best advice?
    Also as my hard disc is nearly full (40 gig) I was toying with the idea of replacing with an 80 gig drive as I don’t really want to cart my external drive around with me everywhere. Are these measures likely to solve the problem or do I have to revert to Tiger? I hope not.

  14. Charles

    Sunday 16 December 2007 at 10:24 pm

    @Ocheye – yes, add more RAM. It improves everything. If you think you can get a bigger disk installed, then do that too. (One easy way to save huge amounts of space is to move your music library – assuming you’ve put it onto your hard drive – onto a spare hard drive, and delete it from your hard drive. Same for movies.

  15. I have a brand new MacBook running Leopard and it is slower than molasses. Gets hung up forever often when app switching. I will try a suggestion or two from herre, but i think I might take it down to the Apple store and compare it with other macbooks…it’s like the old days. makes me want to use the desktop again or ask to go back to Tiger,panther, jaguar or whatever was the last one. DOes anyone else have a new macbook running like a grandma?

  16. my 2004 G4 Powerbook is very sluggish and apt to freeze (esp. using Navigator)…I mostly use my Mac for internet and gaming (WoW). Might be my imagination, but checking the firewall settings sure helped.
    I will try the tips provided here and hopefully will be able to give feedback that it worked.
    Also, really annoying that there is no help whatsoever available through apple or related websites.

  17. I just ran the interface test on xbench once with millions (129.43) once with thousands (145.98)

  18. Hi – it works! I run Archicad 10 on a G5 twin 1.8. I upgraded to Leopard – worst thing I ever did, Archicad runs out of disk space, mail hangs for ever, then did the thousands thing – great. Just realised I have dozens of windows open ad masses of files on the desktop. Each archicad file has about 12-20 windows open, some 3D. Suddenly, I can write this email without waiting 20 seconds between each phrase. Thank you so much. John. PS I play a Rogers Fullerton Blue Strata when not creating buildings