[off topic but appropriate] Re: Can't compile Fortran in Fedora 7

[Mikkel L. Ellertson]

Bruno Wolff III wrote:
> On Sun, Oct 07, 2007 at 12:56:42 -0500,
>   "Mikkel L. Ellertson" <mikkel at infinity-ltd.com> 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.
> 
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.) 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.

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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