[HECnet] Raspberry Pi + SIMH VAX?

[Johnny Billquist]

On 2012-06-03 23:21, Mark Benson wrote:

On 4 May 2012, at 00:07, Boyanich, Alastair wrote:


Sampsa:

Interesting. Be sure to set up the idle detection in the simh.ini for
your appropriate OS (netbsd/TheoLinux/VMS/Ultrix/etc..) or it'll run the
CPU flat-out all the time and potentially get hot. I'm really curious to
hear how 'hot' the R-Pi's get under load. Mine's still on order.
Beautiful idea.

I got my Raspsberry Pi Thursday. It runs SimH 3.9.0 flawlessly under the provided Debian Linux 'squeeze' distribution from a SD Card. The I/O on the RPi isn't fantastic from SD Card, it just about manages 5.5MB/s by most people's benchmarks which is rather slow.

libpcap and screen are installable from the provided arm6l repositories so no need for compiling those. Once I did that I just downloaded the source zip, unzipped it into a directory and used 'make' to build, just like normal. Built fine and runs perfectly.

PDP-11 simulation is plenty snappy enough running RSX-11M Plus 4.2 on a simulated 11/83 with 2048kW of RAM. I have DECNet 4.0 (Phase IV) working on there too and it works fine.

Nice.

VAX KA655X simulation is... sluggish. I'm used to running it on 1.xGHz x86_64 CPUs (Atom or AMD) with fast hard drives or SATA SSD. The CPU speed makes it slow but imagine it's as fast or faster than a real late model VAX. It's by no means perishingly annoying, it just takes a little thinking between operations. I think I may be spoilt as I've never used a real VAX.

It would be interesting to hear of a comparison. The "newer" VAXen are really not that bad. But of course, everything is relative...

Overall so far I'm very impressed with the RasPi and it will fulfil the roles I need for it. When I get hold of a few more I am going to try and build a VMS cluster that uses less than 6W :) I will also have one permanently running a PDP-11 (something that I've not managed since I had my Cobalt Qube2 running) RSX-11MP system.

Talk about doing a misread. I saw that as an RSX-11 MultiProcessor system. :-)

Oh and CPU Idle works just fine in PDP-11 and VMS-VAX simulations. To be honest even when I compiled all the simulator binaries for SimH (as a stress test) and when I was running the SYSGEN in RSX-11M it barely got much worse temperature-wise than hot to touch a the CPU. On a board that only uses 300mA with no USB and Ethernet active it hardly has a lot of energy to dissipate as heat in the first place!

I would suspect that is because the CPU will still be just waiting for I/O lots of the time. Compilations, as well as running something like SYSGEN in RSX, is really I/O intensive. Not much CPU work in there.

	Johnny