2 Jul
2004
2 Jul
'04
1:06 a.m.
>>>> "Tony" == Tony Duell
<ard(a)p850ug1.demon.co.uk> writes:
> Hello list, I'm trying to figure out the boot
sequence on both the
> RK05 and RL02 drive from a PDP. Here's how I understand it so far:
>
> 1. Get the bootstrap in core either via the FP or PTR.
Tony> Or from ROM (originally diode matrix [1]. later on bipolar PROM
Tony> chips)
Tony> [1] Chosen, I am told, because the user could program it
Tony> without special equipment like a PROM programmer. All you
Tony> needed was a pair of cutters (the 'blank' boards shipped with
Tony> all the diodes fitted), and a soldering iron to correct errors.
That's certainly a benefit. Another likely reason is that PROMs
didn't exist yet (only, if anything, mask ROMs, which didn't make
sense in quantities less than 1 million). And even if PROMs existed
back then, 256 diodes were likely to be cheaper.
paul