[TUHS] Can PDP-11/23 PLUS run Unix?

[TUHS] Can PDP-11/23 PLUS run Unix?

[ROBERT MYERS via TUHS]

I’ve just obtained a 11/23 Plus system off of EBay and plan to get a QBone to emulate memory along with a few other things.  I need to know if Floating Point support is a requirement as well if I can also emulate up to 4 Mb of memory.  I’m interested in v6/v7/BSD2.11 for Unix variants.
Sent from my iPhone

[TUHS] Re: Can PDP-11/23 PLUS run Unix?

[Madeline Autumn-Rose via TUHS]

iirc 11/23 lacks supervisor mode so you’d be limited to the 2.9 port with MSCP but it’s been a bit so I could be mistaken

Sent from my iPhone

> On Feb 26, 2026, at 14:52, ROBERT MYERS via TUHS <tuhs@tuhs.org> wrote:
> 
> I’ve just obtained a 11/23 Plus system off of EBay and plan to get a QBone to emulate memory along with a few other things.  I need to know if Floating Point support is a requirement as well if I can also emulate up to 4 Mb of memory.  I’m interested in v6/v7/BSD2.11 for Unix variants.
> Sent from my iPhone

[TUHS] Re: Can PDP-11/23 PLUS run Unix?

[Clem Cole via TUHS]

https://gunkies.org/wiki/PDP-11/23#:~:text=hampage.hu,are%20no%20problems%20with%20this.


To your questions. Because it lacks separate I/D
Space and does not support supervisor mode (only user and kernel) 2.11BSD
will not work.  However V6 and V7 are possible. I think Ultrix-11 should be
able to work and is more likely to have the low level details that 11/23
will need.


Sent from a handheld expect more typos than usual


On Thu, Feb 26, 2026 at 5:52 PM ROBERT MYERS via TUHS <tuhs@tuhs.org> wrote:

> I’ve just obtained a 11/23 Plus system off of EBay and plan to get a QBone
> to emulate memory along with a few other things.  I need to know if
> Floating Point support is a requirement as well if I can also emulate up to
> 4 Mb of memory.  I’m interested in v6/v7/BSD2.11 for Unix variants.
> Sent from my iPhone
>

[TUHS] Re: Can PDP-11/23 PLUS run Unix?

[Madeline Autumn-Rose via TUHS]

v7m is also an option
Sent from my iPhone

> On Feb 26, 2026, at 15:03, Clem Cole via TUHS <tuhs@tuhs.org> wrote:
> 
> https://gunkies.org/wiki/PDP-11/23#:~:text=hampage.hu,are%20no%20problems%20with%20this.
> 
> 
> To your questions. Because it lacks separate I/D
> Space and does not support supervisor mode (only user and kernel) 2.11BSD
> will not work.  However V6 and V7 are possible. I think Ultrix-11 should be
> able to work and is more likely to have the low level details that 11/23
> will need.
> 
> 
> Sent from a handheld expect more typos than usual
> 
> 
>> On Thu, Feb 26, 2026 at 5:52 PM ROBERT MYERS via TUHS <tuhs@tuhs.org> wrote:
>> 
>> I’ve just obtained a 11/23 Plus system off of EBay and plan to get a QBone
>> to emulate memory along with a few other things.  I need to know if
>> Floating Point support is a requirement as well if I can also emulate up to
>> 4 Mb of memory.  I’m interested in v6/v7/BSD2.11 for Unix variants.
>> Sent from my iPhone
>> 

[TUHS] Re: Can PDP-11/23 PLUS run Unix?

[segaloco via TUHS]

On Thursday, February 26th, 2026 at 15:06, Madeline Autumn-Rose via TUHS <tuhs@tuhs.org> wrote:

> v7m is also an option
> Sent from my iPhone
> 
> > On Feb 26, 2026, at 15:03, Clem Cole via TUHS <tuhs@tuhs.org> wrote:
> >
> > https://gunkies.org/wiki/PDP-11/23#:~:text=hampage.hu,are%20no%20problems%20with%20this.
> >
> >
> > To your questions. Because it lacks separate I/D
> > Space and does not support supervisor mode (only user and kernel) 2.11BSD
> > will not work.  However V6 and V7 are possible. I think Ultrix-11 should be
> > able to work and is more likely to have the low level details that 11/23
> > will need.
> >
> >
> > Sent from a handheld expect more typos than usual
> >
> >
> >> On Thu, Feb 26, 2026 at 5:52 PM ROBERT MYERS via TUHS <tuhs@tuhs.org> wrote:
> >>
> >> I’ve just obtained a 11/23 Plus system off of EBay and plan to get a QBone
> >> to emulate memory along with a few other things.  I need to know if
> >> Floating Point support is a requirement as well if I can also emulate up to
> >> 4 Mb of memory.  I’m interested in v6/v7/BSD2.11 for Unix variants.
> >> Sent from my iPhone
> >>
> 
>

Here is a salient document:

https://www.tuhs.org/Archive/Documentation/Manuals/Unix_4.0/Volume_2/F.5.3_UNIX_on_the_PDP_11_34.pdf

Therein Ted Kowalski describes the process of moving UNIX from the
PDP-11/70 to the PDP-11/34, with mentions of the PDP-11/23 also being a
beneficiary of the porting efforts.  If there's not an out-of-the-box
solution already, this paper may be useful in re-porting V6, as would be
referring to Mini-UNIX and LSX, both of which are in the UNIX tree.

- Matt G.

[TUHS] Re: Can PDP-11/23 PLUS run Unix?

[Jay Logue via TUHS]

As others have said, 2.9BSD will run, but 2.11 wont.

Check out the 2.9BSD-MSCP.txt file in this directory: 
https://www.tuhs.org/Archive/Distributions/UCB/2.9-derivatives/2.9BSD-MSCP/

--Jay

On 2/26/26 14:52, ROBERT MYERS via TUHS wrote:
> I’ve just obtained a 11/23 Plus system off of EBay and plan to get a QBone to emulate memory along with a few other things.  I need to know if Floating Point support is a requirement as well if I can also emulate up to 4 Mb of memory.  I’m interested in v6/v7/BSD2.11 for Unix variants.
> Sent from my iPhone

[TUHS] Re: Can PDP-11/23 PLUS run Unix?

[Clem Cole via TUHS]

Absolutely.  v7m was the precursor to both Ultrix-11 and 2.9BSD [2.10BSD
took from Ultrix-11, while 2.8 and 2.9, v7m]. You can even see the emails
from DEC giving the Berkeley team to use anything from either

I suggested Ultrix-11 as I know it has simple (binary) installation media
readily available that supports the 11/23 [sources are also on TUHS].  But
unlike V7m, it was a standard product (supported by DEC at the time)
packaged appropriately  and included a number of enhancements (ie it was a
DEC product and you can even download a PDF of it’s official software
product description (SPD) - which is the official document that described
what DEC would provide support.


v7m was basically a tape distribution by DEC made available to Unix V7
licensees ( and followed the ATT “abandoned on your doorstep” style of
license).  But yes, it supports more models of PDP-11 than the original
Seventh Edition but trying to get it running on real hardware will take
more effort.


Sent from a handheld expect more typos than usual


On Thu, Feb 26, 2026 at 6:06 PM Madeline Autumn-Rose <b4@gewt.net> wrote:

> v7m is also an option
> Sent from my iPhone
>
> > On Feb 26, 2026, at 15:03, Clem Cole via TUHS <tuhs@tuhs.org> wrote:
> >
> > 
> https://gunkies.org/wiki/PDP-11/23#:~:text=hampage.hu,are%20no%20problems%20with%20this
> .
> >
> >
> > To your questions. Because it lacks separate I/D
> > Space and does not support supervisor mode (only user and kernel) 2.11BSD
> > will not work.  However V6 and V7 are possible. I think Ultrix-11 should
> be
> > able to work and is more likely to have the low level details that 11/23
> > will need.
> >
> >
> > Sent from a handheld expect more typos than usual
> >
> >
> >> On Thu, Feb 26, 2026 at 5:52 PM ROBERT MYERS via TUHS <tuhs@tuhs.org>
> wrote:
> >>
> >> I’ve just obtained a 11/23 Plus system off of EBay and plan to get a
> QBone
> >> to emulate memory along with a few other things.  I need to know if
> >> Floating Point support is a requirement as well if I can also emulate
> up to
> >> 4 Mb of memory.  I’m interested in v6/v7/BSD2.11 for Unix variants.
> >> Sent from my iPhone
> >>
>
>

[TUHS] Re: Can PDP-11/23 PLUS run Unix?

[ROBERT MYERS via TUHS]

Can Mini-Uniz run on a 11/23 Plus?  I know it runs on a 11/40.

> On Feb 26, 2026, at 5:19 PM, segaloco via TUHS <tuhs@tuhs.org> wrote:
> 
> On Thursday, February 26th, 2026 at 15:06, Madeline Autumn-Rose via TUHS <tuhs@tuhs.org> wrote:
> 
>> v7m is also an option
>> Sent from my iPhone
>> 
>>> On Feb 26, 2026, at 15:03, Clem Cole via TUHS <tuhs@tuhs.org> wrote:
>>> 
>>> https://gunkies.org/wiki/PDP-11/23#:~:text=hampage.hu,are%20no%20problems%20with%20this.
>>> 
>>> 
>>> To your questions. Because it lacks separate I/D
>>> Space and does not support supervisor mode (only user and kernel) 2.11BSD
>>> will not work.  However V6 and V7 are possible. I think Ultrix-11 should be
>>> able to work and is more likely to have the low level details that 11/23
>>> will need.
>>> 
>>> 
>>> Sent from a handheld expect more typos than usual
>>> 
>>> 
>>>> On Thu, Feb 26, 2026 at 5:52 PM ROBERT MYERS via TUHS <tuhs@tuhs.org> wrote:
>>>> 
>>>> I’ve just obtained a 11/23 Plus system off of EBay and plan to get a QBone
>>>> to emulate memory along with a few other things.  I need to know if
>>>> Floating Point support is a requirement as well if I can also emulate up to
>>>> 4 Mb of memory.  I’m interested in v6/v7/BSD2.11 for Unix variants.
>>>> Sent from my iPhone
>>>> 
>> 
>> 
> 
> Here is a salient document:
> 
> https://www.tuhs.org/Archive/Documentation/Manuals/Unix_4.0/Volume_2/F.5.3_UNIX_on_the_PDP_11_34.pdf
> 
> Therein Ted Kowalski describes the process of moving UNIX from the
> PDP-11/70 to the PDP-11/34, with mentions of the PDP-11/23 also being a
> beneficiary of the porting efforts.  If there's not an out-of-the-box
> solution already, this paper may be useful in re-porting V6, as would be
> referring to Mini-UNIX and LSX, both of which are in the UNIX tree.
> 
> - Matt G.