SCSI card compatibility with PowerMac G4/500 (AGP)
I have kept my 1999/early-2000 PowerMac G4/500 AGP as an office computer only because it has a huge 21" CRT Apple Display, and a number of internal cards and drives and memory & DVD-RW upgrades (plus I couldn't get much for it nowadays). I upgrade my laptops instead (now selling my iBook G4 after just purchasing a new MacBook Pro unibody).
The PowerMac can take a combination of either two ATA + two SCSI internal drives, or three SCSI internal drives in its bays. I already have two 40GB Maxtor ATAs I added years ago (which run
very slowly as I now find that Mac doesn't support more than 27GB ATA well) and the 18GB Ultra2 SCSI Cheetah drive BTO upgrade option from Apple. I've determined it doesn't support more than 36GB SCSI drives well. Since all cards and bays are full except one, I want to fill the remaining SCSI bay with a cheap or refurbished Ultra2 Cheetah, same as one I have but twice as big at 36GB.
To make a long story short (too late, I know!) I have been researching to figure out a few things I didn't know. I kept my PowerMac at OS X 10.3.9 for the last few years and my iBook G4 at Tiger (and new MacBook Pro at Leopard). However, I read the PowerMac can support up to Tiger, so I
finally upgraded the OS to 10.4.11 just a couple weeks ago. At first everything was fine (except for the oversized 40GB ATA's) but then I kept having trouble mounting not only those drives but the shipped SCSI drive. I spent so many days troubleshooting, reformatting, wiping, running numerous pro utility tests, etc. for nothing it seems. The Adaptec dual Ultra2 PCI card that Apple shipped (right before they switched to ATTO) does not support 10.4 (some say not even 10.3 but I had no problems with it then). In fact, Adaptec stopped supporting Macs a while ago, so ATTO is the best bet if I want to stay w/Tiger on that machine (I may just downgrade back to Panther and keep that card). I spent over 30 min. with a nice guy from ATTO on the phone yesterday, trying to determine which cards would both match the maximum my machine can take (Ultra2 or 160 SCSI) but
also run on 10.4
and have the right 68-pin connectors (I need dual channel because I am running an older SCSI 50 Centronics external drive on the first channel and don't want to slow the ultra drive down).
I can find a cheap Cheetah Ultra2 or 160 easy enough online or eBay, but I still am not clear what ATTO card to get, or else stay with the Adaptec and Panther. ATTO's UL2D line (ultra2 dual) would seem right, but some say it might not run Tiger. Their UL3D's are 160 and should work, but still not sure of Tiger and if it I need "VHDCI" or not (or whatever) connecting pins. I definitely
don't want to have to get a new drive
and card
and more internal and/or external SCSI adapter cables too!
LOL, okay.... sorry, guess I had to vent.

Can anyone give me a clue or advice on what card to get or what will work for sure with Tiger, or just revert to Panther on that machine? I did a lot of research and found a lot of good documents on these PowerMacs and SCSI cards on Apple's site and elsewhere, but determining the correct third-party cards and drive capacities to buy
now for a 9-year-old machine is not easy, especially when you also have to take any necessary updated drivers for the Mac OS into account. It looks like the poster here also has the PowerMac w/AGP too though, so thought I'd post. Thanks to whoever made it through this post!
http://support.apple.com/kb/HT3076
http://docs.info.apple.com/article.html?artnum=58429
http://support.apple.com/kb/SP123