Have you ever seen a Pentium? I would not call it small. Certainly an entire motherboard at about 1 sq ft. is not small. Where do you get these quaint notions?
howmuch small..? as suggested it is about 1sqfeet in addition to powersupply .but if u need u can use these to control something , strip-off it t the basic and use dos, embedded linux. beware of the OSs limitations and the control lines/hardware limitations.
what kind of memory could be used that could hold dos or linux, i think about 100 mb should be sufficient. can i use the memory there in pendrives? and ram could be the standard one.
there are DiskOnChip than can hold DOS/linux. It appears as a drive to the system , so that bios will boot from it. A trimmed linux kernel can be less than 1MB