Have done some testing in the last few weeks using X1900XT on a June 2008 MacPro, running Leopard - and also Tiger...

Initial tests revealed that currently available X1900XT cards DO work in 2008 MacPro. Model tested was purchased June 2008. Old X1900XT cards also work once the firmware is updated.

Firmware update available from: http://www.apple.com/support/downloa...areupdate.html

The X1900XT cards supplied as specified with a new MacPro also work (!...)

Tests were carried out under Leopard 10.5.4 with all online updates.

[ you dont want to do this...]
Also tested installing Tiger (10.4.11) on a 2008 MacPro - and initial indications show that it works ok. [ no it doesnt - you dont want to do this ]

Method for installing tiger was to swap the Hard Drive from a 2007 MacPro and put it in the 2008 MacPro. Haven’t actually tried doing a DVD install of Tiger - I use disk images burnt on to hard drives for all my builds. Tiger Hard Drive was initially created on the 2007 MacPro (The Leopard disk also worked in the 2007 MacPro... obviously)

Reasons for test is that there has been a lot of rumors about exactly these subjects. These tests were to establish what works and what doesn’t.
So far, I've not compared performance directly between any hardware/software configuration - so cannot comment directly. Any further feedback welcome

Watch this space...

Simon