[TUHS] Split addressing (I/D) space (inspired by the death of the python... thread)

Will Senn will.senn at gmail.com
Fri Aug 4 08:08:58 AEST 2023


Oh, so... Without I/D, you're stuck with 64k max per process, with I/D, 
you can use 64k for I and 64k for D. Was that it, or were there other 
tricks to get even more allocated (didn't the 11 max out at 256k)?

The kernel could be compiled either with, or without separate I/D. The 
only reason not to is if you didn't have more then 64k or were there 
other reasons?

So, besides the kernel what apps tended to be split? If I remember 
correctly, vi was one, pascal another?



On 8/3/23 16:44, Clem Cole wrote:
> Will its a C Compiler switch (-i) and create 411 files instead of 407.
> I like to refer to it as the 17th address bit.
> I was first brought out with the 11/45 (which was SSI/MSI TTL), and 
> the biggest differences between it and the 11/40.  They were both 
> early 1970s and both of these processors were multiple boards. By 
> 1976, the 780 has started and that sucked off most of the HW folks.  
>  A new hire in 1976, Jeff Mitchell supposedly had a bet with Bill 
> Strecker that he could implement an 11 on a single"hex high" CPU board 
> if he got rid of the lights and switches.  He ran out of room to 
> implement seperate I/D, so it became an 11/40 class [and it has an 
> 8008-1 that runs the front panel].
> The 11/70 came out between the 11/45 and the 34 and had a number of 
> the STAR folks on it it original but it was also multiple boards.   It 
> was not until 11/44 that DEC was able to make a hex height 
> implementation of the 11 that managed to cram a full 11/70 into that 
> system.   The later J-11 chip set took things beyond the 11/70.
> If you look at the conf directory in the sys sources for V6, you see 
> m40.s and m45.s - but if you look at the link line of sys/run the 45 
> does not have -i; but if you look in sys/sys1.c you'll see the in the 
> routine getxfile the support for 0407/0411/0405/0410 files for user mode.
> If you look at the conf directory in the sys sources for V7, you see 
> mch.s and m45.s  its common and the makefile adds -i
> On Thu, Aug 3, 2023 at 4:35 PM Will Senn <will.senn at gmail.com> wrote:
>     Does unix (v7) know about the PDP-11 45's split I/D space through
>     configuration or is it convention and programmer's responsibility to
>     know and manage what's actually available?
>     Will
>     On 8/3/23 12:00, Rich Salz wrote:
>     > What, we all need something to kick now that we've beaten sendmail?
>     > How about something unix, ideally a decade old?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.tuhs.org/pipermail/tuhs/attachments/20230803/b98b956d/attachment.htm>

More information about the TUHS mailing list