Does anyone use RT-11?

Paul Anderson useddec at
Sat Sep 8 22:36:59 CDT 2007

I hope to have it running on an 11/05 and a 11/34 late this year'


On 9/7/07, Jerome H. Fine <jhfinedp3k at> wrote:
> Just as there were inquiries about using PDP-11 hardware, I thought
> that it might be helpful to know if anyone uses RT-11 and for what
> purpose.
> For myself, I have the addiction of fixing RT-11 bugs
> in the operating system as well as making enhancements.
> Ten years ago, I even produced most of the Y2K changes
> that were required for V05.04G of RT-11 for a customer
> who could not wait for Mentec.  Eventually, I want to
> produce a set of Y9K changes to allow years up to 9999
> to be used.
> Other enhancements include SL: and a new pseudo device
> driver, SB: (SymBolic device list device driver) which
> is similar to the VMS SNL (Symbolic Name List), but
> operates only on a device which supports a directory
> as does PATH for DOS.  At one point it was named PH:
> for Path Handler, but SB: seems a better choice.  Even
> more reasonable would be Symbolic device List or SL:, but
> SL: is already used by the Single Line editor (or the DOSKEY
> interface).  Symbolic Debugger is also taken for SD:
> Lately, I mostly use Ersatz-11 and I have been making
> changes and enhancements to the  HD: (Hypothetical Disk)
> device driver that John Wilson originally wrote in 1995.
> The challenge I set myself was to produce a VM(X).SYS
> equivalent that is:
> (a) Faster - about 3 times as fast
> (b) Higher capacity - a full 65536 blocks vs 8192 blocks
> (c) Smaller number of LOADed words in low memory
> (d) Support the command SET VM: [NO]WRITE
> plus a number of other useful features.
> Well, one idea led to another and other versions are also
> being tested which support 8 units and eventually 64 units
> (with monitors that have that support as well).  If there is
> any interest, eventually a translation table similar to the
> one used by DU(X).SYS is possible.  In addition, full 32 bit
> block number support will be done eventually which will
> allow 2 TeraByte disk drives.
> The other HD: related code that is also interesting is the
> ability to interface the HD: device directly from user code
> WITHOUT a device driver.  So while the HD: is about twice
> as fast as DU(X).SYS when a device driver HD(X).SYS is used,
> the direct user interface (which avoids all the overhead of
> a system EMT call) is about twice as fast again.  For this
> user interface, 32 bit blocks numbers are already possible.
> Under a Windows (YEK !! Double YEK) operating system or even
> just DOS, all disk access is completed before the HD: returns
> control to the RT-11 operating system.  Consequently, no
> interrupts are required.  I am not sure about Linux operation,
> but if anyone does know, please advise.
> Sincerely yours,
> Jerome Fine

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