Type 270 disk file on PDP-6

[Eric Smith]

On Mon, Mar 14, 2016 at 1:05 PM, Rich Alderson
<RichA at livingcomputermuseum.org> wrote:
> Device codes were assigned sequentially,

Though assigned sequentially within groups with a different leading
digit, i.e., 0XX, 1XX, 2XX, and 3XX, and (later) some PDP-10
peripherals assigned in 4XX.

> and the disk file control was
> not originally part[1] of the PDP-6 system, so it probably just got the
> next number available.  That some wag decided to use that as the type
> number was more or less likely when it came down the pike.

AFAICT they skipped over 234, 240, 244, 250, 254, 260, and 264, to
give the Type 270 the device code 270.  240 through 264 were later
assigned for DC10 data line scanners, RA10 disk files, and RP10 disk
packs.

270 was later assigned to the RH10 Massbus with RS04 disk.  Presumably
they expected few sites to run both a 270 and an RS04, though the RH10
could be assigned other different device codes, most commonly 274,
360, 364, 370, or 374.