Monday 10 September 2018

The true origin of "the NUXI Problem"

A bit of computer history today.

The Cathedral and Bazaar website defines the NUXI Problem and various other web pages have elaborated on how it is due to endianess of the CPU interacting with data transfer.

All well and good, but the name given to the problem dates from before data transfer. In those days, telecommunications was slow and data transfer was by magnetic tape. So it wasn't due to encountering problems with FTP or something like that, Internet Protocol had not come to Unix yet.

Rather it was named after the glitch observed on the console upon booting up a port of Unix V6 to, my unreliable memory tells me, the Interdata 7/32. The ports were done independently at two places, Bell Labs and University of Woolongong. Here is the story from the veteran of the UW port.

The PDP/11 is little-endian and the recipient of the port was big-endian so when Unix V6 booted up, the message on the console was supposed to be:

UNIX V6...

which came out as:

NUXI...

Obviously a fix had to be applied to the order of bytes within words in compiler generated code for C strings.

I don't know which team encountered this symptom first. The tale was told to me by Piers Lauder, the Unix guru at the time at Basser Dept. of CS at the U of Sydney.

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