I have an IXY 900IS (a.k.a. SD800 IS, Firmware GM1.00E) with a 2GB card. I'm running an iMac with OS 10.4.11. I
I've tried both methods, manual and autoboot. Neither gives me access to CHDK. With the manual method, I noticed the comment in the FAQ, "make sure your card is properly formatted in FAT32 first-- easy way is to format it in the camera". Don't know how that's possible since the camera only formats in FAT16.
That was an error in the FAQ, now fixed. FAT32 isn't required, although would obviously be recommended for cards > 4 gb
I assume that in the manual mode the "Firm Update" option should be at the bottom of the Tools menu. I used BlueHarvest to clean the files even though I used Stuffit to unstuff the archive.
Firm update should appear at the bottom of the first menu you get when starting in play mode. It will not show up if you start in record mode.
If you want to use the "firm update" method, the procedure is very simple:
Format the card in camera
Insert the card in your card reader
Unzip the full install onto the root of your SD card. Be sure to read and understand http://chdk.wikia.com/wiki/FAQ/Mac#You_may_have_issues_with_permissions.
Put the card in your camera
Start in play mode, open the menu and scroll down till you see "firm update" It is usually not visible until you scroll down.
Since your card is 2gb, you can make it bootable from within CHDK, after you start for the first time with firm update.
BTW, this thread probably belongs in http://chdk.setepontos.com/index.php/board,34.0.html
but don't bother starting a new one there. One of the mods will probably move it.