Bootstrapping

For those of you native to the digital world, let me introduce the series of Coral 11 mini-computers, made in Romania by ITC. They were almost perfect "clones" of the PDP-11 series (of DEC), including the rather weird PDP-endian format (a 32-bit integer stored as two 16-bit words in big-endian, but the words themselves are little-endian). Oh, well!

The OS was pretty decent, multi-user real-time, just that... the machine was totally empty, there was no ROM. So, how was it started?

The front panel had lights and switches you had to press to enter a micro code, depositing the address of the peripherical device from where to read the "Bootstrap Loader". To keep it short, the bootstrap loader was a self-modifying piece of code, in assembly MACRO-11:

	LOAD = 0x7400				; Buffer address

0x7744	016701	BEGIN:	MOV	DEVICE, R1	; Get Device CSR
0x7746	000026
0x7750	012702	LOOP:	MOV	(PC)+, R2	; Get buffer offset
0x7752	000352	OFFSET:	0352
0x7754	005211		INC	@R1		; Turn on reader
0x7756	105711	READY:	TSTB	@R1		; Done?
0x7760	100376		BPL	READY
0x7762	116162		MOVB	2(R1), LOAD(R2)	; Transfer
0x7764	000002
0x7766	0x7400
0x7770	005267		INC	OFFSET		; Bump buffer offset
0x7772	177756
0x7774	000765		BR	LOOP
0x7776	yyyyyy	DEVICE:	yyyyyy			; Input device CSR address   

I got my own, on punch tape, the second day at work and I used it a couple years, until the computer's God said: "Let there be ROM!"