[Simh] Rainbow100

[Paul Koning]

> On Jul 20, 2017, at 1:13 PM, Johnny Billquist <bqt at softjar.se> wrote:
> 
> On 2017-07-20 18:58, Paul Koning wrote:
>> 
>>> On Jul 20, 2017, at 11:31 AM, Ray Jewhurst <raywjewhurst at gmail.com> wrote:
>>> 
>>> The DECPro 3xx series (same era I do believe ) is much more interesting than the Rainbow IMO. It runs with either a Fonz or a Jaws (PDP-11 on a chip) It's OSes are POS, a RSX-11M-PLUS derivative, RT-11, 211BSD and Venix, a Unix System III. Good news is there is an old emulator for it called xhomer which you can get at xhomer.isani.org. Also, it does build well on Ubuntu. Not sure on other distros. There is also a fair amount of documentation on Bitsavers. It may be worth looking into.
>> 
>> xhomer is an ancient fork of SIMH with a license problem (hard conflict between the SIMH license on that version and the GPL intended to apply to the PRO mods).  I've tried to see if this can be cured by replacing the GPL, so far no luck though I did get one or two encouraging responses.  It would be good to merge it into SIMH.  Failing that, I suppose a new implementation would (done within SIMH) could be done; the PRO isn't all that hard and the Technical Manual on Bitsavers has most of the answers.
> 
> GPL can be such a headache.

Yes, partly because Bob, very sensibly, doesn't want it in SIMH.  But the strange part in the case of xhomer is that the SIMH base it uses has an earlier "no commercial use" license.  That conflicts with GPL, which technically means that there isn't any license on xhomer, which means that no one is permitted to use it.

> I could perhaps be persuaded to help out some, if you go for reimplementing this, Paul.
> 
>> I've been wanting to add to the PRO emulation, stuff like Ethernet, or the obscure PC3XC 4-line UART card, or PRO-380.  But right now there is no place to do that.
> 
> The single most annoying thing about the PRO (well, of course there are so many with this machine) is the crippled state of the PRO-380. Here you have this nice J11 CPU, and then they still have the same support chips as on the 350, meaning you're running at a slow speed, and with P/OS you cannot use the split I/D-space, nor the supervisor mode.
> Not sure if it would work ok if you did your own software.

Yes, it does.  My RSTS works fine and uses the J-11 extra capabilities.

The slow speed is a different matter.  I was told at the time that the support chip designers assumed that they could run synchronous to the J-11 internal clock, so they used a 10 MHz clock in the support chips, expecting the J-11 to deliver the promised 20 MHz speed grade.  Oops -- Harris only delivered 17 MHz.  So they had to go down to the next lower multiple of 10 MHz, which is 10 MHz, and that is supposedly why the Pro-380 runs at that slow speed.

> Also, since the device drivers for the PRO specific things seems to have gone missing, I have no idea if it would be possible to build a new version of P/OS which could take advantage of the -380 hardware, but I've been peeking a little in the RSX sources about this a few times...
> 
> If only DEC had made that machine like a normal PDP-11...

Yes...  The saddest part is that, as far as I remember, the CT bus supports DMA but no PRO I/O device ever built uses it.  All are programmed I/O, except for Ethernet which uses a card-resident dual port memory.  That last approach is pretty decent, too bad the Ethernet chip they used is the worst Ethernet chip in history -- it has major architecture errors that were obvious to people at least as early as 1964.

	paul