360/50 microcode listing

Dave G4UGM dave.g4ugm at gmail.com
Thu May 7 13:07:52 CDT 2015

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jon Elson
> Sent: 07 May 2015 18:17
> To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and Off-
> Topic Posts
> Subject: Re: 360/50 microcode listing
> On 03/13/2015 01:32 PM, Al Kossow wrote:
> > CHM was able to obtain volumes 18-20 of the IBM 2050 drawings, which
> > are the microcode charts and ROS dump. I got them scanned and uploaded
> > yesterday to http://bitsavers.org/pdf/ibm/360/fe/2050
> >
> > This was one of the things that I had been trying to locate for a
> > while now.
> >
> >
> Just a curious thing I've noticed.  Given the historic significance, and the large
> number of machines produced, I'm kind of amazed at the incredibly small
> number of 360's that apparently exist.
> Yes, I know, any would-be collector could drag home a PDP-8 and put it in his
> garage, even a whole rack mount system with an RK02 (or 3), dectape and
> paper tape reader, and still get his car in the garage.  And, the system could
> be run off normal mains power.
> You can't do that with a real 360 (some 360/20's were pretty small), even a
> 360/30 was a pretty big box.  And, you can't run a 360 off normal residential
> power, either.  Many of the peripherals used 3-phase motors, and hacking
> the converter/inverter to run off single phase would not be a task for any but
> the most experienced EE.
> But, it sure is a shame that there appear to be a tiny number of machines in
> existence.  One list shows 15 or 16 machines, excluding the model 20.
> Probably there are a couple more hidden somewhere, like the B1900 that
> came to light so recently.
> As fas as I can tell, NONE of these systems is complete enough to ever run,
> with the possible exception of the
> 360/30 at the CHM, which does seem to have a complement of peripherals,
> and maybe control units, too.
> Given the number of DEC 10's that are actually up and running, this seems a
> bit of a surprise.  there might be some emotional attachments that are
> behind this disparity.
> Anybody have some comments?

I think that you are not comparing like with like. How many KA10's are there left as that’s the DEC System/10 that’s comparable with the S/360. If you want to compare IBM Mainframes with DEC System/10 then you need to include S/360, S/370 and 43xx boxes. Now there may be few S/360's but there are 370's and I am sure there are many 43xx boxes.

However I think that the quantity of preserved mainframes is dire when compared with other items of "technology" history. There are hundreds of preserved static steam engines, steam locomotives, vintage ,  veteran and classic cars or automobiles (not that vintage and veteran have specific definitions in relation to cars/automobiles), radios and TVs etc. I am sure there are more concorde aeroplanes and possibly even space shuttles than there are S/360's...


> Jon

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