Computermuseum der Fakultät Informatik


R.B.W.s Helploader


How comes software into PDP8/L?

Because the PDP8/L has no external storage device and no ROM with a
bootstrap-loader, the user has to enter a loader program on the front
panel before first time using the machine or if a program accidently 
has overwritten the whole memory.
This loader should be as short as possible!

The shortest loader I know, (except the  RK8E boot loader) is Robert B.
Websters revised helpstarter:

0027 6031
     5027
     6036
     7440
     2036
     7012
     7010
     3006
     5027

BTW, the disassembled helpstarter is appended to the source of the help-
generator!

These nine words are to be entered into memory starting with address 0027.
Program start is word 0027. The program loads the HELPLOADER, which itself
loads an arbitrary loader, for example the BINLOADER at address 7600 into
memory. HELPLOADER and the special coded BINLOADER are packed together in
File HLPLDR.PT.

For verification I added an octal dump of the helploader. The BINLDR is
also present and the source of the helploader generator.
Both of them are not necessary, it is sufficient to toggle in the HELPSTARTER
and then read in the HELPLOADER either from papertape by a real Teletype or
from a PC with for example KERMIT or PROCOMM. My PDP8/L has no problems with
9600 Bd.

BINL3 is a slightly modified version of the original DEC-binloader:
Startaddress is 7600 or 7605, it loads PAL8-generated .BN files with the
exception of field numbers. (Sorry, my 8/L has only 4K of core).
It indicates the actual address in AC, so I can observe the progress of
loading a file. If loading has finished, the loader stops before a JMP
to address 0200. In most cases it is simply sufficient to press the switch
'CONT' on the front panel to start the loaded programm.

Commonly I'm using my LAB8/E as development system and fileserver for the
8/L and the 8/L in reverse as I/O-processor to control the IBM 735 type-
writer or the Tektronix 4015-terminal.


Instructions for KERMIT: I'm using MS-DOS Kermit Vers. 3.10 13 March 1991. Use of kermit as video terminal is trivial: (full duplex, VT100- emulation and so on). binary upload as follows: 1. Enter the helpstarter on the front panel, start it at address 0027 2. Start KERMIT, in command-mode make sure (with 'stat') if: Speed: 9600 <- or what the PDP8 likes Parity: none (8-Bit-data) Local echo: off Flow control: xon/xoff handshake used: none set eof-mode: noCtrl-Z 3. command to KERMIT: transmit hlpldr.pt or, if the BINLOADER is in memory: transmit file.bn 4. transmit doesn't finish by itself, you have to press ctrl-c if you think that the upload is finished. Hint: The file hlpldr.pt is not in .bn-Format and can only be loaded with the helpstarter. A .bn-Files in my understanding are the files which are generated by PAL8 (for example). to Homepage of Computermuseum