Subject: Re: Most perverted DEC system: DECsystem 5500
To: Michael Kukat <>
From: Magnus B{ckstr|m <>
List: port-alpha
Date: 10/30/2002 14:44:02
Congratulations, you've discovered the DEC5500's console processor!

It's a VAX, and yes -- it can boot operating systems.  The VAX lives on
the QBUS and can access that bus just as the R3000 system module can;
its main purpose is to run diagnostics.  If you have SDI or DSSI disks
you can even log on and speak to them with SET HOST/DUP <...>, etc.

But the console processor is not the one you want to boot netbsd on,
except for purposes of showing off :-)

IIRC, you log off the VAX and return to the R3000 console program by
simply typing 'EXIT'.  In the pmax console you go to the VAX with
with the 'MAINT' command.  The pmax console should show you a '>>'
prompt, as opposed to the '>>>' VAX prompt.

As a rule, you get the pmax console by default; some self-test errors
can cause the VAX to take over though.

The VAX console processor in the 5500 continued an old DEC tradition,
e g the VAX780 and 8600 series had LSI11 console processors.  The 8600
console processor would boot RSX without much fuss, even while an OS
was running on the VAX...

Somehow DEC liked to install the previous generation of machine as
console controller in their current generation.  A somewhat disagreeable
twist in this tradition imo was the console controller of the VAX85xx
machines -- they were DEC "Personal 350" things which ran its own OS
and a special, rather buggy, application to poke around inside the VAX
cpus.  The console would crash every so often, and when it came back up
it would not always respect the privacy of the VAX cpu already running

On Wed, 30 Oct 2002, Michael Kukat wrote:
> Hello,
> okay, i aquired a DECsystem 5500 at eBay now. After fixing a burned operator
> panel, this thing seems to work nice. But i saw an _EXTREMELY_ perverted
> curiosity:
> Trying to boot Ultrix/RISC: ?FILESTRUCT somewhat
> Trying to boot NetBSD/pmay: ?FILESTRUCT somewhat
> Okay. I know this message from a VAX trying to boot from a non-FILES11-disc.
> So i thought: okay. Getting rid of this message is easy: Throw in a
> FILES11-disc. The system will crash, but for testing, if my CD-ROM is okay,
> this is enough. So i inserted Ultrix/VAX.
> And i didn't believe it: This beast boots Ultrix/VAX!!! Extremely slow, but
> boots. Okay, the kernel halts when starting, but this thing executes VAX code.
> Same with VMS/VAX. It starts booting and terminaltes with %SYSBOOT-F-Unknown
> Processor or so. But it executes VAX code. As a final test: Booting NetBSD/vax
> on it. The bootloader display the usual text, the counter goes down, okay but
> then, it fails with stray interrupts. But this is the definitive prove that a
> DECsystem 5500 with a MIPS R3000 inside is capable of executing VAX code, maybe
> even emulate a VAX.
> So, should we, besides port-pmax, also port NetBSD/vax on this machine? Just as
> a nice gag? Okay. I have the hardware now, so i will have a look into the
> kernel to drive DS5500 support, according to the website, it is still in
> progress. I don't know if i find the time to port NetBSD/vax on it also, but i
> will have a look into NetBSD/pmax.
> But, besides this funny story... Is there a way to boot the official
> Ultrix/RISC from CD on this machine? "B DIA3" doesn't work, and the RZ devices
> aren't recognized in several forms, but are displayed in "SHOW DEV".
> ...Michael
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