RT-11 idle light pattern

Paul Koning paulkoning at comcast.net
Sun Dec 31 09:21:01 CST 2017

> On Dec 31, 2017, at 9:41 AM, Noel Chiappa via cctalk <cctalk at classiccmp.org> wrote:
>> From: Paul Koning
>> RSTS-11 V4, which had a major reliability problem ... As part of trying
>> to keep the customer placated, DEC supplied full OS sources, 5
>> dectapes. ... We printed them ... I still have copies of those files.
> Is that version available online? If not, maybe an OCR project?

I don't know; if not I should dig through mine and submit it to Bitsavers.  I don't have the original DECtapes, but rather a copy of the files on magtape, so metadata is largely missing but the actual files should be there.

> (Although I know other versions of RSTS-11 are available, so maybe it's not
> rare enough to make the tedium of OCR worth it. That has been used on a
> number of systems; notably CTSS, but also the IMP code and the Apollo
> Guidance Computer, that I know of. I'm currently looking into getting an
> early version of MERT, and that may also come down to OCR - if we're lucky!)
>> Stranger still is the "fancy" lights in RSTS ... "Fancy" because it
>> produces a rotating pattern not just in the data lights which is easy,
>> but also in the address lights. It runs in supervisor mode
> Ah; it must busy loop at loops spread across the address space? Clever!
> (Perhaps using the mapping hardware so that it doesn't use too much _actual_
> memory.) Is the source available?

Correct, it uses the MMU so it only needs 64 bytes of table space to get the low order bits right.  See attached.


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