[mvapich-discuss] PCI-X vs PCI-Express compile options:

[Troy Telford]

I've never really concerned myself much with how MVAPICH has different  
configurations for PCI-X and PCI Express; that is changing however.

It seems that the difference is in a particular define (_PCI_X_ vs.  
_PCI_EX_); and the only differences are #ifdefs in vbuf.h.  Looking at  
vbuf.h, it seems there are only two differences:
	1.)  VBUF_TOTAL_SIZE is different
	2.)  viadev_vbuf_total_size is also different.

A casual observation is that when MVAPICH is compiled to use PCI-X, it  
still works on PCI Express hardware (with the same speed for the small  
number of nodes I was using).

Could somebody more knowledgeable of the workings of MVAPICH enlighten me  
as to how important it is to compile it for the correct bus?
-- 
Troy Telford