Requiem for PC/104

The PC/104 stackable-board standard is dying. Not because it isn’t useful. PC/104 boards still constitute a $400 million/year market according to Micro/Sys president Susan Wooley. PC/104 has hit the wrong end of the bathtub because it’s based on the original IBM PC ISA bus and the last processors and chip sets to support that bus have been discontinued. Fade out associated bus standards.

What’s to replace PC/104? How’s “stackable USB” sound? Yes, sounds weird to me too. However, it’s got a lot of positives. Even though it’s a serial protocol, the USB 2.0 electrical spec employed by the proposed Stackable USB standard provides 462 Mbps of effective throughput, which is much faster than the parallel ISA bus. Further, the USB 2.0 protocol will likely be around for a while. In addition, use of the USB communications protocol makes the Stackable USB proposal far more independent of the associated processor architecture.

Stackable USB boards have the same form factor as PC/104 boards so existing enclosures might be reusable (although the connectors are different, which may complicate matters). For more info, go to www.stackableusb.org.