EDSAC as early as 1949 had an "initial orders" module. A boot-up ROM. There was a bank of rotary selector switches, to set the octal digits in each ROM word.
David Wheeler (of subroutine fame) figured out the most sensible thing to put in the tiny ROM was a paper tape loader and mini-assembler that loaded the rest of itself from paper tape. So at switch-on the machine would start reading the tape input and run. Programs could be written on the teletype with mnemonics and relative addresses in octal.
It seems a little strange that more advanced later machines like the original PDP-11 from 1970, couldn't "autostart" from ROM like that. You had to toggle in a bootloader.
I think that was because core memory was non-volatile. (EDSAC didn't use core; it had a refreshing DRAM-like delay line memory.) With core, you only had to toggle the bootloader into once and, provided your software didn't accidentally overwrite it, it was still there after a power cycle. So re-toggling in the boot loader was not really that common, despite how much lore surrounds it.
In Fred Hoyle’s science fiction novel, The Black Cloud, there is a computer in an early chapter that is clearly inspired by EDSAC. When they run a program on it, the process is just what you describe - they load a paper tape in through the tape reader, which Hoyle describes in detail.
I first read that book before I knew that in British English a vacuum tube is called a valve (from thermionic valve and which makes more sense than the American term, I think), so I was confused by the line about how warm the room was due to all of the valves!
We called them thermionic valves too, just the terminology shifted a bit over time. We also called capacitors "condensers". Both were references to steam powered control systems.
retrac · · focus · HN ↗
David Wheeler (of subroutine fame) figured out the most sensible thing to put in the tiny ROM was a paper tape loader and mini-assembler that loaded the rest of itself from paper tape. So at switch-on the machine would start reading the tape input and run. Programs could be written on the teletype with mnemonics and relative addresses in octal.
It seems a little strange that more advanced later machines like the original PDP-11 from 1970, couldn't "autostart" from ROM like that. You had to toggle in a bootloader.
I think that was because core memory was non-volatile. (EDSAC didn't use core; it had a refreshing DRAM-like delay line memory.) With core, you only had to toggle the bootloader into once and, provided your software didn't accidentally overwrite it, it was still there after a power cycle. So re-toggling in the boot loader was not really that common, despite how much lore surrounds it.
rootbear · · focus · HN ↗
I first read that book before I knew that in British English a vacuum tube is called a valve (from thermionic valve and which makes more sense than the American term, I think), so I was confused by the line about how warm the room was due to all of the valves!
monocasa · · focus · HN ↗
rootbear · · focus · HN ↗