I read somewhere that IBM is #1 server vendor, but I guess it depends on how you
count. A mainframe can be considered to be a server, and that is how IBM probably becomes #1.
The number of s/390 and z-series servers sold annually is probably in the low 4 figures
and the associated hardware revenue is probably a couple of billion. So I don't think it
affects the server rankings by units at all, and by revenue by much.
Where IBM makes its big money on mainframes is in highly leveraged drag-on software
and services and I don't think this shows up as server revenue.