12 Mar
2016
12 Mar
'16
8:52 p.m.
I just was looking at the I/O device code assignments in the 1973
DECsystem-10 System Reference Manual, and happened to notice the entry
for the Type 270 disk file used on the PDP-6.
PDP-6 and PDP-10 device codes are three octal digits, of which the
third digit can only be 0 or 4.
The device code for the Type 270 is octal 270. Coincidence? :-)
14 Mar
14 Mar
12:05 p.m.
From: Eric Smith
Sent: Saturday, March 12, 2016 8:52 PM
I just was looking at the I/O device code assignments
in the 1973
DECsystem-10 System Reference Manual, and happened to notice the entry
for the Type 270 disk file used on the PDP-6.
PDP-6 and PDP-10 device codes are three octal digits,
of which the
third digit can only be 0 or 4.
The device code for the Type 270 is octal 270.
Coincidence? :-)
Probably. Kind of. More or less.
The disk file is called a 5022. The 270 is the disk file *control*, and
yes, it has device code 270, but it attaches to the data control type 136
(device code 200). Other things connecting to the 136 are the microtape
control type 551 (device codes 210 and 214) and the magnetic tape control
type 516 (device codes 220, 224, and 230).
Device codes were assigned sequentially, 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.
Rich
[1] Based on the fact that it was built using Flip Chips, initially
invented for the PDP-7, rather than System Modules (either the kind
used in the PDP-1, PDP-3,[2] PDP-4, and PDP-5, or the extended kind
invented for the PDP-6).
[2] Remember that while DEC did not build a PDP-3, a customer rumored to
have been a front for the NSA did. DEC sold designs as well as actual
hardware in the early days.
Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134
mailto:RichA at LivingComputerMuseum.org
http://www.LivingComputerMuseum.org/
9:25 p.m.
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.
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