Another computer

Ages ago, I decided to build a new computer from an Intel D410PT motherboard that I bought. I was (and still am) going to install it as a PDP-11 emulator. Anyway, I built the machine but never got round to installing an OS on it. Actually, I did try to see if it would run Windows 7 ... but Windows was not happy with being installed on a USB flash drive as a boot disk.

But, since recently I've gotten used to Debian, I thought that I'd try that. This is an OS that is very happy to boot from a USB flash drive. This is cool, since I can swap hard disks for the machine without even mucking about with screwdrivers. Here is the machine running Debian 6 off a small 4GB flash drive I bought in Tesco:

So... here are the things that I actually bought to build it:

  • Intel D410PT motherboard (with integrated Atom processor)
  • 1GB Kingston Technology 667MHz DDR2 memory
  • LinITX mini-ITX case inc wall mount and power supply CFI-ACD29CC

...all that stuff cost me £103.00 including the shipping costs. I only had to add the USB flash drive for storage (but I already had that lying around). It's not as pretty as a mac mini, but it's still quite a small little machine. All the software I've used is free, so I have Debian 6 (squeeze) coupled with Google Chrome and it quite happily streams TV channels through BBC iPlayer and other services like TV Catchup. So at the moment it's working as a nice cheap little media centre. The next step is to install SIMH and start emulating some old hardware...

Adding Basic-11 to RT-11 in SIMH

This post continues with my SIMH RT-11 tutorial... To add Basic-11 into the mix I've been using this image of the "Languages Master" RX50 floppy disk.

Download that disk image to the folder where you've saved pdp11.exe.  Next, we're going to add that floppy to SIMH.  We can do that by editing the ini file.  Just before the line that reads "boot rl0", we need to add this line:

attach rl1 languages.dsk

This will mean that in RT-11 the Languages Master disk will appear as "DK1:", whereas the boot disk is "DK0:", the RT-11 install disk.  Test it out by running pdp11.exe and typing DIR DK1: (and pressing enter) at the command prompt.  You should see the directory listing of the languages master disk.

Before we try and install Basic, we need to make sure that we're using the RT-11 extended monitor, so type in these commands into RT-11:

copy/boot dk0:rt11xm.sys dk0:
boot dk0:

This should restart RT-11 in the extended monitor (RT-11XM).  When this disk is booted in future it will remember this setting.  Now we can actually install Basic, enter these commands:

copy dk1:b*.* dk0:
copy dk1:*.bas dk0:


...you should see the files being copied to your boot disk.  Now we're ready to try Basic-11.  Try this command:

basic

You should see this:

BASIC-11/RT-11 V02-03
OPTIONAL FUNCTIONS (ALL, NONE, OR INDIVIDUAL)?

I normally respond by typing ALL (in capitals), in which case Basic responds with "READY".  We have Basic!

We can now type in Basic programs, try this one:

10 FOR I=0 TO 12.6 STEP .2
20 PRINT TAB(30+COS(I)*30);"HELLO WORLD"
30 FOR S=0 TO 1000 \ NEXT S
40 NEXT I
50 GOTO 10
RUN

Press <CTRL>+C quickly twice to stop the program when you've got bored.

To leave Basic-11 the easy way, just type BYE at the READY prompt.

[EDIT: if you're looking for some information on Basic-11, I've posted some documents here.]

[ANOTHER EDIT: the PDP11.co.uk website, where I originally got the image of the languages disk from seems to have been shut down. I have changed the link above to a cached version from the wayback machine. And if you want to see the complete software page from PDP11.co.uk then you can still see it here.]

Starting RT-11 in SIMH for the first time

This post continues my SIMH RT-11 tutorial... When you start RT-11 from the install disk the first time, you'll see some text like this:

Welcome to RT-11 V5.3

You have bootstrapped the RT-11 Distribution Disk.  Use this disk to
install your RT-11 system, then store it in a safe place.

RT-11  V5.3  provides an automatic installation procedure which will
back up your distribution disk and build a working system disk which
should  be  used for your work with RT-11.
This  working  system disk will only  contain  the  RT-11  operating
system.  After  the  RT-11  installation  is  complete,  follow  the
installation instructions  packaged  with  any optional languages or
utility software which you will be using.

Press the "RETURN" key when ready to continue.


I usually try to skip the automatic install procedure, since I'm more likely to learn stuff if I do all the setting up by hand.  So after pressing RETURN, and getting asked "Do you want to use the automatic installation procedure?" I type "NO".  After pressing RETURN a couple of times, we should be booted into RT-11.

Remember, if you ever mess up your boot disk and things go wrong, you can just re-copy a fresh version of rtv53_rl.dsk and we will get back to the start point above.

Emulating RT-11 in SIMH

I was asked if I could write some instructions describing how to get RT-11 to boot in an emulator, so here goes...

To boot a PDP-11 in the SIMH emulator (on Windows), the first thing you need is a copy of the SIMH program.  You can get that from here: http://simh.trailing-edge.com/sources/simhv38-1-exe.zip

From that zip file we're interested in the application called "pdp11.exe", you should easily find it inside the root of the zip file.  Extract pdp11.exe to a folder on your PC - this is the SIMH emulation of a PDP-11.  It won't do anything interesting yet though.

The next thing that you need is some software to run on the emulator, I've been using the RT-11 OS and you can download that here: http://simh.trailing-edge.com/kits/rtv53swre.tar.Z

That is a compressed set of RT-11 files, including a disk image.  Inside, there should be a /Disks folder containing the disk image called "rtv53_rl.dsk".  Save that dsk file to the same folder where you saved pdp11.exe.

Now we need to tell SIMH to boot, and to do that we create an ini file and save it into the same folder as pdp11.exe.  You can do that in notepad.  The ini file should have this content:

set rl enable
set cpu 512k
set cpu 11/53
attach rl0 rtv53_rl.dsk
boot rl0

Save that content as "pdp11.ini" in the same folder as everything else.  It will tell SIMH to emulate a PDP-11/53 with 512k or RAM, and boot from the disk image.

Now you should be able to run pdp11.exe and it should boot from the disk and start running a brand new copy of RT-11.  You're on your way...