VAX-11730 (was Any word on OS/2 for PDP-11?)

[Ethan Dicks]

On Wed, Feb 06, 2008 at 08:12:11AM -0800, Bob Armstrong wrote:
> >Ethan Dicks wrote:
> 
> >The 11/730 (and 11/725) has an on-board FEP - an 8085.  You talk to
> >it much in the same way as you do to the LSI-11 in an 11/780, except
> >its console medium is TU58 tape, not RX01 disk.  Syntactically, though,
> >I believe it's similar (I know the KA730 well, but not the KA780).
> 
>   Indeed, the 730 CFE (Console Front End or FEP) was very much like the 780
> - the commands were similar and the 730 even used indirect command files for
> functions like booting and power up loading of microcode.  All the
> microstore on the 730 was RAM; the only ROM was a little EPROM that booted
> the 8085 operating system from the console TU58.  Everything else - all the
> CPU microcode, the microcode for the IDC (integrated disk controller) the
> FPA microcode, and VMB - were all loaded from the TU58.  Although the 8085
> operating system was some custom thing DEC wrote themselves, the TU58s used
> an RT11 file system (again, just like the 780) and you could easily
> manipulate them with EXCHANGE or FILEX.

That all sounds familiar.
 
>   The bad news was that TU58s are really, really, slow.  With all the
> microcode and indirect files that had to be read from the TU58, your 730
> could easily take ten minutes from power on to the point where VMB was even
> ready to start thinking about loading VMS.  When working on one, you want to
> do everything you can to avoid turning off the CPU box power:-)

Using the stock console tapes from DEC, that was absolutely true.  One of
the scripts I wrote a while back, built a load-order optimized console tape.
I think the 8085 must cache the directory, since the tape doesn't seek back
to the directory blocks between each file.  With the files in the right order,
the file transfer time doesn't change, but the file-to-file time is just about
nil (I think there may be one seek from end-to-end because of how many files
there are to read and the block interleave on the tape).
 
>   Because everything about the KA730 microcode was "soft", it's fairly easy
> to change the CPU microcode, update the console TU58 and reboot to change
> the CPU behavior.  I believe DEC even sold a set of microprogramming tools
> for the 730, but I've never seen them and I don't know what's become of them
> today.

Back in the day, I remember occasionally seeing docs on PDP-11 microcoding,
but I don't recall seeing anything for any model of VAX.

-ethan

-- 
Ethan Dicks, A-333-S     Current South Pole Weather at  6-Feb-2008 at 19:20 Z
South Pole Station
PSC 468 Box 400       Temp  -48.6 F (-44.8 C)   Windchill   -75.5 F (-59.7 C)
APO AP 96598          Wind    8.2 kts Grid 50   Barometer 675.4 mb (10802 ft)

Ethan.Dicks at usap.gov            http://penguincentral.com/penguincentral.html