Editing Transputer (section)

=== Booting ===
Transputers could boot from memory, as is the case for most computers, but could also be booted [[network booting|over its network links]]. A special pin on the chips, BootFromROM, indicated which method it should use. If BootFromROM was asserted when the chip was reset, it would begin processing at the instruction two bytes from the top of memory, which was normally used to perform a backward jump into the boot code. If this pin was not asserted, the chip would instead wait for bytes to be received on any network link. The first byte to be received was the length of the code to follow. Following bytes were copied into low memory and then jumped into once that number of bytes had been received.

The general concept for the system was to have one transputer act as the central authority for booting a system containing a number of connected transputers. The selected transputer would have the BootFromROM permanently asserted, which would cause it to begin running a booter process from ROM on startup. The other transputers would have the BootFromROM tied low, and would simply wait. The loader would boot the central transputer, which would then begin sending boot code to the other transputers in the network, and could customize the code sent to each one, for instance, sending a [[device driver]] to the transputer connected to the hard drives.

The system also included the 'special' code lengths of 0 and 1 which were reserved for [[PEEK and POKE]]. This allowed inspection and changing of RAM in an unbooted transputer. After a peek, followed by a memory address, or a poke, with an address and single word of data, the transputer would return to waiting for a bootstrap. This mechanism was generally used for debugging.