[K12OSN] oldest feasible client pc? p166 reasonable?

[light being]

I installed a P166 as a client that for some reason seems ridiculously slow, 
even doing odd things.

What's the oldest client that's actually reasonable to use normally?

Long ago I had read tall stories about 486 and 386 clients, but nowadays it 
seems that the Celeron-300  / 32mb ram I have is about actual minimum... 
even they crash unless I enable the NFS-swapping in fact.

Ideally I am noticing the a client needs a 400mhz CPU and some 64mb ram...

Is there some thinner kernel or X.org to use somewhere that is still 
practical?

Seems there is some fat to cut in these kernel images.