Did you know you can change the order the tiles render in AutoCAD 2008? Of course on a single processor this is not really all that fun, but on a multi-core machine it can be cool and mesmerizing.
I have always wanted to say mesmerizing. ;-)

Perhaps you just assumed that the seemingly random order of the tiles was meant to be and never cared to explore and find the setting. I have my paranoid suspicions that the reason the tiling order was not set to spiral by default is that Autodesk was scared it could be contacted by many lawyers claiming their poor clients were hypnotized and fell off their chair or that their employees went into a non-productive trance when rendering so of course Autodesk took the safe route and set the default to the Hilbert tile order instead.

Ok now how to change from Hilbert to Spiral. Go into the Advanced Render Settings (RPREF) then scroll to the bottom of the palette to the processing section and change the setting of tile order to spiral.

Notice I am using a dual dual core (4 processor cores) when rendering. The tiles are actually each processor.

disclaimer: I am not liable for any hypnotic trances or injuries that arise from setting the tile order to Spiral. ;-)