Project PDA

Universal System Bus. A device that connects a PDA to a computer.

Port of data transmission, much faster than the serial or infrared. Uncommon among the PDA of the Palm brand. Through this port can be synchronization between PDA and computer.

When the Digital Equipment Corporation and its hardware designers conceived the UNIBUS, its capability to accept and interpret interruptions to the OS was highest on their list of things they wanted... so a four-level hardware interrupt scheme was born; the first in the minicomputer world.

• To accomplish this, they created the UNIBUS, and its hardware-interrupt scheme. To do this, however, wasn't exactly simple in that day and age of simple (and expensive) logic chips. So they decided that any peripheral card (or set of cards) could assert an 'interrupt' on one of four levels on the system bus (UNIBUS or UNIversal system BUS)... and the software would sort it out. Remember, there wasn't any 'microcode' in those early days..
• The bus lines delivering the interrupt signals had to get to the processor cards via the system bus; so what happened if you weren't using a bus slot? It happened often in those days, thanks to dedicated backplane slots.
• Enter the Grant Card; it was simply a bit of Printed Circuit card that allowd an interrupt to cross an unoccupied bus slot.