Re: [off topic but appropriate] Re: Can't compile Fortran in Fedora7

On Mon, 2007-10-08 at 17:30 -0500, Mikkel L. Ellertson wrote:
Bruno Wolff III wrote:
On Sun, Oct 07, 2007 at 12:56:42 -0500,
"Mikkel L. Ellertson" <mikkel@xxxxxxxxxxxxxxxx> wrote:
Richard England wrote:
I believe he was referring to the bank of switches on the front panel of
his computer by which you could set the memory locations, thereby
entering the boot program.

Boy what a pain that was.

I agree, they were a pain to use. But they were not DIP switches. I
have used both toggle and rocker style switches, but not DIP switch
on a front panel.

PDP8's had toggle switches. It's been a while, but what I remember is that
you first set a mode switch to load the address, then you switched to a load
data mode and you would set up the data and hit a load toggle that would
load the data and advance to the next address.
Usually you would load a few bootstrap instructions, then load a simple loader
from paper tape, then load a more advanced loader from paper tape, then load
your program.

PDP-11s had toggle switches with big plastic rocker covers on them so
they LOOKED like rockers but really were toggles.

The Altair 8800 and 6800, the SWTC 6800 and several other "personal"
computers also had toggles set up in octal. The IMSAI 8080 had rockers
that you could set up in octal or hex.

If I remember right, up was deposit, and down was deposit next. The
first would leave the address the same, and the second would
increment it. (It would also wrap back to 0.)

Actually:

1. Set the start address on the switches
2. Hit "EXAMINE"
3. Set the instruction word
4. Hit "DEPOSIT"
5. Set next instruction word
6. Hit "DEPOSIT NEXT". This first incremented the address, then
stuffed in the instruction word.
7. Repeat steps 5 and 6 until you went insane or got the whole boot
loader switched in.
8. Reset back to starting address
9. Hit "EXAMINE"
10. Hit "RUN"
11. Cross fingers and sacrifice a goat for good measure.

On PDP-11s, you would set up the address, EXAMINE, RUN and up would
pop the ODT (octal debugging tool) on your trusty DECWriter-II.

The basic loader was
something like:

Set pointer for data destination.
Check serial port for data.
No data, loop back to check.
Get data from serial port
Store data in memory.
Increment data pointer
Loop back to check.

I believe the paper tape loader of choice was a model 33 teletype on
a 20ma current loop.

Oh, lordy do I remember those animals! 10 bytes/second! I finally
broke down and bought a manual optical paper tape reader for my Altair.

Later down the road, I got an UVEPROM card with the Zapple monitor and
could talk to a VTI interface to my TV (16 lines x 64 characters!)
Eventually, I had a Tarbell cassette interface (worked well) and when
iCom came out with their 8", 271KB floppy drives, I bought a set.

Ah, memories! (this was all in 1976-78).

----------------------------------------------------------------------
- Rick Stevens, Principal Engineer rstevens@xxxxxxxxxxxx -
- CDN Systems, Internap, Inc. http://www.internap.com -
- -
- Any sufficiently advanced technology is indistinguishable from a -
- rigged demo. -
----------------------------------------------------------------------

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