MacOS 10.6 “Snow Leopard” Review

I’m a member of the Apple Developer Connection, which gives me access to Apple’s “developer preview” releases of MacOS.  The latest release, launched today, is version 10.6 (dubbed “Snow Leopard“).  I’ve been running the last developer preview (build 10A432) for two weeks now.  Though developer previews are subject to Apple’s NDA, the non-disclosure terms do not apply to publicly-available programs and information.  Fortunately, a friend of mine found that his fresh install of the retail disk that arrived from Apple today is also build 10A432 (that is, the publicly available disk is identical to my installation).  Because my experiences reflect those of use with (what is now) a publicly-available product, I can share those experiences now.

Though this is not a comprehensive review, these are my perspectives as an end user.  Overall, I like the responsiveness, disk-space efficiency, and (as a geek) the promise of improved capabilities through the rearchitected (“refined”) kernel.  I had severe data-loss issues with Exchange support such that I would strongly advise caution before using it in a critical setting, and I had a couple of kernel panics that are troubling.

Installation went smoothly and took about an hour.  I ran the installer from within my pre-existing 10.5.8 installation on my Core 2 Duo Late 2006 iMac, which has 4GB of RAM.  I disliked the fact that the installation of Rosetta (Apple’s mechanism for emulating PowerPC execution so that you can run older applications written for PowerPC on Intel hardware) is disabled by default.  I thought they could do something more intelligent like look in your /Applications folder and check for PowerPC applications.  It’s a minor issue, however — I had read that this was a known change, so I enabled the optional install.  More serious to me was that the installation deleted Xcode.  I suppose this, too, was an optional installation, but this seems rather stupid.  It’s Apple’s software that ships as part of a fundamental part of the operating system.  If you’re upgrading the rest of the OS and are saving settings and so on, why on earth was Xcode passed over?  I reinstalled it after I discovered it was gone, but finding my basic tools (gcc et al.) gone was disturbing.  The installation initially did seem to reclaim about 6GB of disk space, but after reinstalling Xcode, the difference was negligible.  Allegedly the major source of reclamation is removing unused printer drivers and installing them on-demand instead, but since I had already removed them, it makes sense that I missed out on the big disk-space savings.  I also installed 10.6 on my late-2006 Macbook Pro, which roams more often and therefore I’ve left the printer drivers on it.  The disk savings was closer to the claimed 6GB on that machine.  Regardless, both worked fine with my networked Brother laser printer after the upgrade.  The installer no longer gives installation-type choices (“upgrade in place”, “archive and install”, “erase and install”) — it just does an upgrade.  Apparently you *can* “erase and install” manually, if you erase your disk before booting the DVD, but that’s not the method I chose.

After installation, the first thing I did was configure Mail to use my work email account, which is hosted on an Exchange 2007 server.  This is probably the big user-noticeable feature that’s added in 10.6, which is otherwise mostly a rearchitecting of the kernel with very few user-visible changes.  I was very excited about Exchange support.  For those that don’t know, Exchange integrates calendaring, a user database, and email.  All information is stored on the server and fetched by the client, so that you can have multiple clients connected to one server, yet they all have a synchronized “view” of your account’s email, calendar, and contacts.  It’s a Microsoft standard, and frankly it’s annoying to use because there are so few non-Microsoft clients.  I had been using (the Rosetta-requiring) Entourage 2004 client, which is functional but has a terrible interface and is slow.  Setting up my account was trivial.  Mail quickly started fetching my mail, and before long my calendar was synchronized with iCal as well.  Exchange contacts were accessible as expected in Mail, and things seemed to “just work” — until they didn’t.

About 3 days after using Mail, disaster struck.  Somehow, one of the clients (either my iMac or Macbook Pro) was out of sync and deleted several folders worth of email from the server.  I lost about 3000 emails, possibly permanently.  (I’m in the process of finding out from our IT group how difficult it might be to restore them, since I know that our email is archived as per Sarbanes-Oxley compliance).  Most of these were not critical emails, but this was extremely troubling.  I immediately disabled my Exchange account on my 10.6 clients.  Apple’s bug-reporting tool has been broken for weeks, so I’ve no idea if they’re making progress on this issue.  Worse, a backup could not save me — it’s a synchronization bug that wipes out your emails on the server.  I haven’t seen anyone else report this issue.  Obviously I looked in the trash (on all my clients) and saw nothing — this clearly seems to be some sort of bug in the synchronization mechanism Apple is using.  I have perhaps 15,000 emails on my account, and I do wonder if their testing has overlooked cases like this.  I also have about 20 filtering rules (for mailing lists), which may have complicated the issue, and I always have several clients connected to the server simultaneously (usually my Outlook 2007 client at work, my iPod Touch, and then my laptop & iMac at home).  Regardless, I’ve been doing this with Outlook and Entourage for a long time now and have never encountered this, so I’m definitely chalking this up to some sort of bug that Mail either has or triggered in the other clients.  The take-away point is that users should be extremely cautious of using Mail for their Exchange accounts until Apple releases an update that mentions something about improved Exchange support.  I certainly won’t be using that feature until then.

Other than Exchange support (which is unusable for me now), changes are subtle.  There’s a new look to context menus for items in the Dock, which was the only interface issue I noticed as different.  Window decorations and the Finder look identical to 10.5.  Bootcamp adds support for reading HFS+ volumes from Windows, which is nice.  The other major differences are all under the hood.  I did not do any benchmarking, but threading and context switching seem much, much faster.  (I hate reviews that say useless crap about how something “feels snappier” — how is that quantified, exactly?  It always seems to be in the reviewer’s head).  Specific things that I noticed as improved was the responsiveness of Expose and the Dashboard.  The Finder has been rewritten in Cocoa, which may also explain its speed improvements.  And surprisingly, Firefox 3.5.2 is much more responsive on 10.6 than 10.5.  Opening new tabs is far quicker than before, and I get far fewer “spinning beachball” pauses when I’ve got lots of tabs open on Safari or Firefox.  These perhaps are the effects of scheduler and memory allocation improvements in MacOS — things that have, traditionally, been kind of crappy in performance, and which seem to be addressed in the marketing material for 10.6 (things like the “Grand Central” multicore dispatch mechanism, which seems to reveal heavy work on the scheduler).  10.6 also has support for a 64-bit kernel and extensions, but my hardware does not have a 64-bit implementation of EFI and therefore is not compatible with Apple’s 64-bit kernel.  (It’s possible to run a 64-bit kernel on 32-bit EFI, but Apple isn’t supporting it, which is fine.  Even on machines where a 64-bit kernel is supported, it likely does not make sense to enable it by default until drivers and 3rd-party extensions have a formal, rigorous qualification process).  Likewise, my graphics hardware does not support Apple’s hardware-accelerated h.264 playback, so I can’t comment on that, either.  Unlike the 64-bit kernel, I do hope that Apple aggressively rolls out expanded hardware support for this acceleration to other models.  It may well be that Apple will support these features on all new Macs, which would be great.  Now, they are of limited (or nonexistent) value for upgraders.

Unfortunately, the architectural and performance improvements aren’t all ideal, either.  When using Safari on a guest account that I was testing, I managed to trigger a kernel panic (!) twice when using the “Top Sites” feature, which I normally disable on my own account.  Unfortunately, this feature is enabled by default.  Thinking it was a fluke, I tried again, and boom, panic() again.  Apparently Apple has not taken the advice from my blog (that is, “don’t panic()”).  🙂  Again, I haven’t seen other reports of this issue, but I have not had stability problems on this hardware for the 2.5 years I’ve had it, including some 3D graphics use.  The panic log showed that the failure occurred in, therefore this may be a graphics-driver issue.  I say “may” because any other driver in the system could’ve DMA’d memory into the driver earlier that caused the eventual fault.  It’s tough to say.   So, it would seem that a few corner-case bugs still require addressing.  In the meantime, I’m disabling “Top Sites” everywhere and will be on the lookout for an update.  I’m also going to beware of 3D graphics, actually.

So to summarize, these are the Pros and Cons from my experience — on newer hardware, I’d think that the “Pros” would also include hardware acceleration for h.264, but perhaps an update will come with that.


  • Improved application responsiveness
  • Disk space reclaimed
  • HFS read support from Windows (via Bootcamp driver)


  • Potentially catastrophic Exchange support
  • Mysterious kernel panics that seem graphics-related (using Safari’s Top Sites feature)
  • Features that seem tightly restricted to a small-ish subset of installed hardware (h.264 hardware acceleration, OpenCL support)

On the whole, it seems a fairly solid point-zero release (10.5.0 had its share of troubles).  The only potentially glaring problem is if the Exchange issue is encountered by many more people, given that it is the primary end-user feature of this release.  I’m hopeful for an update on this issue and perhaps hardware acceleration for h.264 as well.

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