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--- systems:pdp7_unix [2015/12/29 23:55] – wkt
+++ systems:pdp7_unix [2015/12/30 00:09] – wkt
@@ Line 36: / Line 36: @@
 So that every user did not need to maintain a link to all directories of interest, there existed a directory called //dd//  that contained entries for the directory of each user. Thus, to make a link to file //x//  in directory //ken//, I might do
-<code>ln dd ken ken
+<code>
+ln dd ken ken
 ln ken x x
 rm ken
@@ Line 131: / Line 132: @@
 The very convenient notation for IO redirection, using the `>' and `<' characters, was not present from the very beginning of the PDP-7 Unix system, but it did appear quite early. Like much else in Unix, it was inspired by an idea from Multics. Multics has a rather general IO redirection mechanism [3] embodying named IO streams that can be dynamically redirected to various devices, files, and even through special stream-processing modules. Even in the version of Multics we were familiar with a decade ago, there existed a command that switched subsequent output normally destined for the terminal to a file, and another command to reattach output to the terminal. Where under Unix one might say
-<code>ls>xx
+<code>
+ls>xx
 </code>
@@ Line 148: / Line 150: @@
 The only extant source code from the PDP-7 version of Unix appears to be the source code to the //dsw//  command that Dennis [[http://minnie.tuhs.org/pipermail/pups/1999-November/000139.html|posted on the net.unix-wizards]] Usenet newsgroup in 1984. He wrote:
-I happened to dredge up an old notebook and found a listing of the PDP-7 version of dsw.  Because several people have approached me recently about reviving a version of PDP-7 Unix as a sort of paleontological exhibit, and because the subject has been discussed here, I thought people might be interested in seeing the code. I first considered net.sources, but decided not to carry whimsy too far.
+I happened to dredge up an old notebook and found a listing of the PDP-7 version of dsw. Because several people have approached me recently about reviving a version of PDP-7 Unix as a sort of paleontological exhibit, and because the subject has been discussed here, I thought people might be interested in seeing the code. I first considered net.sources, but decided not to carry whimsy too far.
 Notes:
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   - "sys save" makes a core image.
-<code>" dsw
+<code>
+" dsw
    lac djmp
@@ Line 197: / Line 200: @@
 In October 2009, Dennis sent Warren Toomey a private e-mail that said "In other news, I have found the book that has the [PDP-7] listings that I knew I had, that of (some) of the user-level commands. I wonder what's the best way to get it scanned?". Unfortunately, Dennis passed away before he could get the listings scanned in.
+===== PDP-9 Unix =====
+In several places, including the [[http://www.tuhs.org/Archive/Documentation/Papers/unix_cacm74.pdf|CACM paper]], there is mention made of Unix running on a PDP-9. Dennis Ritchie posted [[http://minnie.tuhs.org/pipermail/pups/2002-August/000529.html|a message on the PUPS mailing list]] in August 2002 which said:
+The [PDP-]7, 9, 15 were very compatible.  I think the -15 had some scheme for using an index register, which the earlier ones didn't have, but it was otherwise pretty much identical in IS architecture.
+There was very little rewriting to try Unix out on the -9 and -15; perhaps just some tweaks in
+the disk device commands.  I don't think the system actually ran on either for more than a few hours. Ken was just playing around.
+The -15 may have had an electrically different bus, but I'm reasonably sure it was not a Unibus. All of them used IOT instructions, not memory-mapped IO registers.
+Both of the machines we tried were being used by other groups and we couldn't squat on them as with the PDP-7. I recall that  the -15's main job was controlling a step-and-repeat camera that exposed LSI masks.