SCSI options for PDP 11/23

From: Jerome Fine <>
Date: Sat Mar 2 22:40:15 2002

>Tom Leffingwell wrote:

> >On Wed, 27 Feb 2002, Zane H. Healy wrote:
> > OK, what I see that concerns me is the fact you're using a 11/03 box.
> > Unless I'm mistaken the 11/03 was only Q16, which has me wondering how
> > you're even running a 11/23 CPU, which should be Q18, in it (it's possible
> > someone upgraded the backplane to be 18-bit).
> It did have the M8186 11/23 CPU in the 11/03 chassis when I got it, not
> that that means anything. I did change the memory module to a 128KW
> MSV11-LK.

Jerome Fine replies:

As long as you are able to run the RT11XM and it recognizes that there
are 248 KBytes (the last 8192 Bytes are lost to the IOPAGE in an 18-bit
system, then you definitely are running with an 18-bit backplane. If by
chance you had all 256 KBytes of memory, that would mean that you
had a 22-bit system. The command:
SHOW MEMORY (or just SH M)
will provide the information you need as might the boot information.

> There's an older Q-bus VAX system at the University that will probably be
> taken out of service soon, and there's a chance I can grab its SCSI
> controller (I'm not sure exactly what it has, but I know it has one).

You should be aware that a CQD 220/TM is no longer available and that
manuals are difficult to obtain. Ask on the list and we can help if that is
the version of the host adapter. If possible, get your dibs in early so
that you can grab it when it becomes available.

> > I took a quick look and it looks like CMD made SCSI controllers that would
> > work in either a Q18 or Q22 system. It also looks like Viking controllers
> > only work in a Q22 system.
> > As for your Fortran programs, I would think they would work on V5.x, but am
> > not sure. The best people on the list to know about that would be Megan or
> > Jerome.
> > Is this a hobbyist system, or is it a production system?
> Its mostly a hobbyist system, in that I paid for it personally, and if it
> weren't for it being a hobby, I would have given up a long time ago. :)

>From what I know of FORTRAN IV programs and V4.00 vs V5.00
compatibility, you are VERY unlikely to have a problem. Assume for
now that you won't - which is an assumption I rarely make in any
circumstances. That means that I have so rarely found a problem
that for most cases it is just not an issue.

Your bigger problem will be to transfer the files to a SCSI hard drive.
I will volunteer to put V5.03 on a SCSI hard drive for you if no one
else is available in the US. Since I am in Toronto, crossing the border
could be a complication. But ANYONE else who is able to write
to a SCSI hard drive on either a real PDP-11 or anyone who has a
Full version of E11 can also do that for you. A SCSI hard drive is a
SCSI hard drive on any system. Under E11, I can connect the same
2 GByte ST32550N drive from a real PDP-11 to a header on the
SCSI cable to an Adaptec AHA2940AU PCI host adapter. I do
need to "trick" the software by having a Sony SMO S501 powered
up on the same SCSI ID when I first boot Windows98 and load
ASPI8DOS.SYS for E11, but after I turn off the power on the
Sony SMO S501, I can power on the ST32550N (the SCSI cable
may NEED to be plugged in first - I always do) hard drive and
E11 is very happy to use the ST2550N as an RT-11 device.

> Its kind of hard to explain, but I'll try. I work for a university on a
> National Science Foundation funded project that provides satellite
> communication to scientists at the geographic south pole, and a few other
> assorted places in the Antarctic. Normal commericial satellite
> communication isn't affordable to the scientific community, so the
> operation uses old satellites (ranging in launch year from 1967 to 1977)
> that are no longer usable for their original purpose, such as imager
> failures in the case of the older GOES satellites. We also use ATS-3, the
> oldest continously operating satellite in the world. It took the first
> color pictures of the earth from space in 1967. Also, being low on
> station keeping fuel, which causes the orbit to drift north and south of
> the equator, so that it its no longer geostationary is another reason.
> That's good for us, because at geostationary orbit, you can only see down
> to about 80 degrees south. With the drift, you can see the poles for
> about 6 hours a day.
> In order to perform maneuvers (fire the jets) on a spin-stabilized
> satellite, you have to synchronize your commanding with a reference point
> (usually the sun). If you were in the 1970s and wanted to design a
> reliable "portable" computing system for each launch site required around
> the world, what would you use? You guessed it, a PDP-11. The software
> was on an RX02 along with RT-11.
> Anyway, we built our own command equipment awhile ago with a small
> microcontroller. This was intended for commanding where the timing isn't
> critical, such as turning things on and off, switching sensors, etc. The
> attitude of a spinning satellite precesses slowly over time, and you
> correct it by firing jets in a synchronized manner, which we can't do with
> our equipment. The attitude starting to be off enough to where it needs
> to be corrected. Lacking the funding to develop something new, combined
> with everyone assuming I wouldn't be able to revive this system, I decided
> to rebuilt it on my own. (We only had a few pieces of the original system
> that attached to the DMA and PIO interfaces, which didn't work, and none
> of the PDP equipment). It was working pretty well until the RX02
> incident. I was hoping I could scrape up a SCSI controller from somewhere
> around the university, so I could have a longer-term storage option. So
> in the next couple of months, it will get used for a "production" purpose,
> but then it won't be needed for quite awhile.

I have never quite head your complete situation. Anything else I can help
with? If anyone could provide a loan CQD 220/TM for a few months,
might that help? SCSI hard drives are not the problem - the ST32550N
cost only $ US 10.00 and plenty of others are also available.

I can't understand how funding can be so tight that a project which uses
a $ 100 million satellite can't find the support for a PDP-11 system
at this point. Doe someone nearby have a BA23 box that they can
provide you. That will be a problem to some extent since you should
also have at least an M8189 (quad 11/23 with boot ROMs). But
I would be willing to send that to you if more memory would also
help. Otherwise, if 1/4 MByte of memory is sufficient, then your
present system with a SCSI host adapter and hard drive will likely
serve you very well.

If you need any more help with RT-11, please ask here at any time.

Sincerely yours,

Jerome Fine
Received on Sat Mar 02 2002 - 22:40:15 GMT

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