X Windows performance on PI

[HOUFAC]

Does anyone know how the Turbo Graphics option affects X-windows performance
on a Personal IRIS? (For applications running locally -- not across a network.)

I've heard that IRIX 3.2 provides a big improvement, but I'm looking for
all I can get.

I'm already planning a 20MHz CPU upgrade -- any idea how much that'll help?
Is X CPU-bound or graphics-bound??

Thanks!  --Pete Poorman