PDP-11 booting, RL02 working!

Edward quapla at xs4all.nl
Mon Jan 2 14:37:19 CST 2006

You've got an XXDP+ diagnostics pack :)
Very usefull to check out your new PDP-11!


> More "operator error". Sometimes I think I have mild dyslexia.
> The RL02 Fault and Ready lights stayed on which is usually a sign
> of bad cabling (lost clock). Although I had carefully aligned the
> IDC connectors while making my substitute RL02 ribbon cable, I
> thought I'd save some effort by using a 40 pin header as a
> male-male connector directly to the Berg connector (that mates
> with the drive bulkhead connector inside).
> However - after considerable schematic, DVM and scope work I
> belatedly discovered that this connects the headers in a mirror
> image and although left/right can be swapped by turning over the
> ribbon cable, the two rows are now swapped as well! The four
> corner pins are 3 grounds and the BPOK H signal. Wrong cabling
> doesn't hurt anything on the RL8E since the power-ok circuit has a
> 100 ohm resistor in the collector of the driver transistor. But on
> the RLV12 there is no protective current limiting and the PNP
> transistor (MPS-A55) is turned on hard between +5 and the (short
> to) ground! Fortunately it just got hot but didn't fry, although
> it might if it'd taken me much longer to figure out the trouble :)
> Anyhow this time when I powered up there were no lamps lit on the
> RL02 (normal) and after the requisite 15 sec. powerup the Load
> light came on. I crossed my fingers and pushed the Load button and
> the drive spun up and the Ready lamp lit. So far so good.
> So I flipped the restart switch on the CPU, answered "Y" to
> "Start?" and got a message "Please boot from system disk". I have
> one other disk pack that is known to have come from a PDP-11, so I
> put it in the drive - lo and behold, "Booting up XXDP-XM Extended
> Monitor" followed by ... "V2.4, Rev. E1, booted from DL0, 124Kw
> memory, Non-Unibus system, restart address 152000, type H for
> help".
> Looks like I now have a working PDP-11 :)
> The pack has 727 files on it whose names are meaningless (to me
> anyway). XXDPXM.SYS etc. is obvious but there are hundreds of
> files from A to Z with names like "VKMHA0.BIN", "ZAFAC0.BIC" and
> some .LIB and .OBJ files too.
> What on earth do I have here? Is it something that anyone would be
> interested in copying?
> -Charles

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