Well, the most limited RAM SBC *I* know of is the Beagleboards: the
BeagleboardBlack and Pocket Beagle as 1/2Gig. Early model RPis have 1Gig of
RAM. Note: it is possible to include swap space on these machines on their
uSD cards (but probably not recomended).
"man 7 pipe" says that since Linux 2.6.35, the default pile size is 16 pages, i.e., 65,536 bytes. It can be changed by using the fcntl(2) F_GETPIPE_SZ
and F_SETPIPE_SZ operations, but it's unlikely the OP's sending program changed it to more than 16 pages.