The introduction of ¼-size and ½-size StackableUSB boards also solves the CPU cooling

dilemma. The challenge with higher power Pentium-class single board computers (SBC) on the 104 form factor has been providing cooling to the CPU when an I/O board is plugged on top and completely covers the CPU chip, trapping heat and seriously reducing air flow. Extending the CPU board outside the 104 footprint has been one approach that has lead to form factor

introductions such as the EPICTM form factor and EBXTM form factor. Now, however, between the spaced gained with the smaller StackableUSB connector and the greater exposed board space

with ½- and ¼-size I/O boards, the 104 form factor becomes more viable for Pentium-class SBCs.

In order to accommodate the smaller StackableUSB form factors, a fifth stabilizing hole has been added to the 104 foot print definition. By including a fifth centrally-positioned hole on the 104 board, smaller StackableUSB I/O boards can be incorporated into a stack to form a structurallysound,full-featured systems. These can be a space saving of nearly ¾ the size of the same

system implemented with the traditional 104 form factor boards with a cost savings up to 60%

since less parts and physical PCB board are used. Currently Micro/sys offers the USB1700 in

the ¼-size board and StackableUSB CPU boards with the fifth stabilizing hole PC/104

definition.