Hi,
I was the lead developer of the CMS (internally SL9) MCP working in Cumbernauld from 1972 thru 1978. The SL9 software (MCP, compilers, utilities) was planned from the start to run on B80 (Cumbernauld), B800 (Downingtown) and B1800 (Liege) series. That was achieved by each plant writing a suite of microcoded interpreters to emulate the same virtual machine for compiled COBOL and MPL bytecodes. [This concept is now used for the Java Virtual Machine and others.] The MCP kernel was hand coded (in microcode) at each participating plant to a common spec - the "SL9 virtual machine".

It was important to build a "real" MCP lookalike with commands like MX, AX, OK, DS etc. so that the field would not need a lot of training. We diverged from Burroughs MCP practice in one small way: the leading EX on the execute command was optional, so anything the MCP "didn't understand" was considered to be a program name to be executed [as nowadays in *nix]. This allowed the "outer parts" of the MCP actually to be utilities written in MPL and thus interpreted.

Getting authority to create an MCP (multiprocessing OS) for a 64k byte accounting machine was a hard (internal) sell. The thesis was that these machines would have a single owner so did not need much (actually any) logging/accounting, and would run a max (on the B80) of 16 concurrent tasks. Thus we could get by with one byte instead on one 48 bit word for most OS data items. The CMS versions of the B80 (it also ran SL5 which was an L machine emulator) had a hard disk which was used for a virtual memory system as well as an MCP filing system. Designing from the ground up for multitasking and virtual memory probably saved this project multiple times both pragmatically and politically.

To me the most satisfying moment was when I led a mission to Downingtown to negotiate some fine points of the SL9 VM spec. While I was being met and greeted, two software engineers I'd brought along walked over to the B800s which they had never seen, and started operating them fluently. Now /that's/ compatibility.

Aside from some very talented colleagues, I would not have been able to pull this project off without a solid previous background in medium and large systems MCP support, having installed and tended both the first B3500 and first B6500/B6700 in Europe.

Hope this has some interest. I note that Wikipedia has no mention of this commercially successful Burroughs product family.

P.S. SL7 was the predecessor software written at Downingtown for the B800 series,

Duncan Fenton <shannock9@gmail.com> writes:
>Hi,
>I was the lead developer of the CMS (internally SL9) MCP working in Cumbern=
>auld from 1972 thru 1978. The SL9 software (MCP, compilers, utilities) wa=
>s planned from the start to run on B80 (Cumbernauld), B800 (Downingtown) an=
>d B1800 (Liege) series. That was achieved by each plant writing a suite of=
> microcoded interpreters to emulate the same virtual machine for compiled C=
>OBOL and MPL bytecodes. [This concept is now used for the Java Virtual Mac=
>hine and others.] The MCP kernel was hand coded (in microcode) at each par=
>ticipating plant to a common spec - the "SL9 virtual machine". =20

Was the B874 DCP that we used on Medium systems based on the B800?

On Tuesday, August 16, 2022 at 3:48:18 PM UTC-7, Duncan Fenton wrote:
> Hi,
> I was the lead developer of the CMS (internally SL9) MCP working in Cumbernauld from 1972 thru 1978. The SL9 software (MCP, compilers, utilities) was planned from the start to run on B80 (Cumbernauld), B800 (Downingtown) and B1800 (Liege) series. That was achieved by each plant writing a suite of microcoded interpreters to emulate the same virtual machine for compiled COBOL and MPL bytecodes. [This concept is now used for the Java Virtual Machine and others.] The MCP kernel was hand coded (in microcode) at each participating plant to a common spec - the "SL9 virtual machine".
>
Have you kept any documentation, or software?

I'm trying to fill in my documentation collection from the product series and I have almost nothing on the later machines.
Oddly, I did come across schematic sets.

On Sunday, May 7, 2023 at 8:27:58 AM UTC-7, Al Kossow wrote:
> On Tuesday, August 16, 2022 at 3:48:18 PM UTC-7, Duncan Fenton wrote:
> > Hi,
> > I was the lead developer of the CMS (internally SL9) MCP working in Cumbernauld from 1972 thru 1978. The SL9 software (MCP, compilers, utilities) was planned from the start to run on B80 (Cumbernauld), B800 (Downingtown) and B1800 (Liege) series. That was achieved by each plant writing a suite of microcoded interpreters to emulate the same virtual machine for compiled COBOL and MPL bytecodes. [This concept is now used for the Java Virtual Machine and others.] The MCP kernel was hand coded (in microcode) at each participating plant to a common spec - the "SL9 virtual machine".
> >
> Have you kept any documentation, or software?
>
> I'm trying to fill in my documentation collection from the product series and I have almost nothing on the later machines.
> Oddly, I did come across schematic sets.

CHM recently received several binders full of sales brochures for the CMS and accounting machine products. I've been working on scanning them and uploading to http://bitsavers.org/pdf/burroughs. This information doesn't appear to be available anywhere else on the web.

Al Kossow <aek@bitsavers.org> writes:
>On Sunday, May 7, 2023 at 8:27:58=E2=80=AFAM UTC-7, Al Kossow wrote:
>> On Tuesday, August 16, 2022 at 3:48:18=E2=80=AFPM UTC-7, Duncan Fenton wr=
>ote:=20
>> > Hi,=20
>> > I was the lead developer of the CMS (internally SL9) MCP working in Cum=
>bernauld from 1972 thru 1978. The SL9 software (MCP, compilers, utilities) =
>was planned from the start to run on B80 (Cumbernauld), B800 (Downingtown) =
>and B1800 (Liege) series. That was achieved by each plant writing a suite o=
>f microcoded interpreters to emulate the same virtual machine for compiled =
>COBOL and MPL bytecodes. [This concept is now used for the Java Virtual Mac=
>hine and others.] The MCP kernel was hand coded (in microcode) at each part=
>icipating plant to a common spec - the "SL9 virtual machine".=20
>> >
>> Have you kept any documentation, or software?=20
>>=20
>> I'm trying to fill in my documentation collection from the product series=
> and I have almost nothing on the later machines.=20
>> Oddly, I did come across schematic sets.
>
>CHM recently received several binders full of sales brochures for the CMS a=
>nd accounting machine products. I've been working on scanning them and uplo=
>ading to http://bitsavers.org/pdf/burroughs. This information doesn't appea=
>r to be available anywhere else on the web.

Hm. That's the first time I've heard of the B4500, I had thought that the
high-end medium systems started with the B4700; granted the B4800 had been
in service for a few years when I started at Pasadena.

I have one of the C3316 calculators (nixie tubes) which still works,
albeit some of the keys are sticky (shown in the products of burroughs 1967).

scott@slp53.sl.home (Scott Lurndal) writes:
>Al Kossow <aek@bitsavers.org> writes:
>>On Sunday, May 7, 2023 at 8:27:58=E2=80=AFAM UTC-7, Al Kossow wrote:
>>> On Tuesday, August 16, 2022 at 3:48:18=E2=80=AFPM UTC-7, Duncan Fenton wr=
>>ote:=20
>>> > Hi,=20
>>> > I was the lead developer of the CMS (internally SL9) MCP working in Cum=
>>bernauld from 1972 thru 1978. The SL9 software (MCP, compilers, utilities) =
>>was planned from the start to run on B80 (Cumbernauld), B800 (Downingtown) =
>>and B1800 (Liege) series. That was achieved by each plant writing a suite o=
>>f microcoded interpreters to emulate the same virtual machine for compiled =
>>COBOL and MPL bytecodes. [This concept is now used for the Java Virtual Mac=
>>hine and others.] The MCP kernel was hand coded (in microcode) at each part=
>>icipating plant to a common spec - the "SL9 virtual machine".=20
>>> >
>>> Have you kept any documentation, or software?=20
>>>=20
>>> I'm trying to fill in my documentation collection from the product series=
>> and I have almost nothing on the later machines.=20
>>> Oddly, I did come across schematic sets.
>>
>>CHM recently received several binders full of sales brochures for the CMS a=
>>nd accounting machine products. I've been working on scanning them and uplo=
>>ading to http://bitsavers.org/pdf/burroughs. This information doesn't appea=
>>r to be available anywhere else on the web.
>
>Hm. That's the first time I've heard of the B4500, I had thought that the
>high-end medium systems started with the B4700; granted the B4800 had been
>in service for a few years when I started at Pasadena.

Ah, I've been informed that the B4500 was the planned name, but by the
time it went to FCS (First Customer Ship) it had been renamed from
the B4500 to the B4700 (and core memory had been replaced by
semiconductor memory).