Looking Ahead to OS X Snow Leopard

Here is a piece looking at what's known about the next release of OS X, 10.6 aka Snow Leopard:

Mac OS X Snow Leopard 10.6 - the story so far | News | TechRadar UK

The focus is largely on performance -- graphics, multi-core, etc. Which raises one question with me. What's up with OS X grinding to a halt whenever there's any I/O?

By which I mean... when copying files from one disk to another, or pictures off a compact flash card, or Time Machine starts doing a backup... everything seems to come to a stop. I might expect that some other I/O-bound process could become twice as slow, or even 5x as slow if there was contention on the same disk for writing things like browser cache files, causing seeking back and forth.

But my perception is that it's worse than that. Browser windows freeze completely until Time Machine is finished. Operations slow to a crawl when I'm pretty sure they're not touching the disk that's being copied to or from. Pictures take forever to come off a compact flash card when nothing else is tying up the processor. You would think it would be an obvious optimization to make Time Machine run at a low priority when the foreground app was doing I/O, or to speed up copies between compact flash cards and Firewire external drives, where the internal drive shouldn't be involved at all. Yet in this one area, I find Windows beating OS X in speed.

I don't know if it's something deep within BSD, like you periodically hear some bugaboo in Linux internals that makes certain operations really slow. I've seen these slowdowns when copying or moving files both from the Finder and the Terminal.

Memories, of a PC2-5300 DDR2 667 DIMM...

You know it's time to upgrade memory in the new Intel iMacs when it starts to make noise. Every switch between one big program and another involves grinding and endless waiting. Even switching to Finder or Terminal can be interminable. You start regretting keeping all your songs in one iTunes library, or keeping Firefox open with a week's worth of backlogged tabs.

Unfortunately, the stock memory comes as 2 512MB modules. Meaning any upgrade you do means selling or otherwise disposing of one or two old memory chips. You can upgrade from 1GB to 1.5GB by swapping in one 1GB module, or to 2GB by swapping in two 1GB modules. Upgrading to 3GB is way too expensive still, with 2GB modules running from about $600 all the way up to $900+.

The little latch door on the bottom of the iMac screen is easy to get off with a small eyeglass-size screwdriver. The screws are attached to the door so they can't get lost. The old modules come loose when you push on a couple of plastic levers. If you don't seat the new modules firmly enough, when you power up you won't hear the chime and the light flashes steadily. Since you might have to fiddle around with the chips a couple of times, leave the latch off until you've successfully powered up again.

With the extra memory in, you should see an immediate speedup in application switching or user switching. An application like Photoshop can be running a batch job while you switch over to iTunes or Firefox with everything running at full speed and no grinding (technically, paging).