[[..]
>the write stops. I don't know yet what cause this (if it's
>activity to swap partition, or if it's some file that the X system has to read
>for each event, or such).

Manelu,

Just a stab in the dark, but: can you try mounting the /dev directory
with noatime/nodevtime/whatever-it-is we recommend laptop users do, to
avoid spinning-up/writing to disk to update dev times?

If nothing else the xterm is going to trigger updates to the
last-access time on its pty, every time top refeshes the display.

(followups probably to tech-kern..)

--Jonathan