strange number corruption on pdp11/34

Don North ak6dn at
Fri Jan 30 15:37:05 CST 2015

-----Original Message-----
>From: Noel Chiappa <jnc at>
>Sent: Jan 30, 2015 5:19 AM
>To: cctalk at
>Cc: jnc at
>Subject: Re: strange number corruption on pdp11/34
>    > From: Don North
>    > So here is the octal print routine in the M9312 console boot prom for
>    > the '34:
>I'm curious, is that the 'original' source, or is this dis-assembled from the
>PROM contents? Is the complete program available somewhere?

Disassembled and re-commented source. Available here:

along with most all of the other M9312 boot and device PROMS.

>    > So I would speculate either 'rol' or 'rolb' are always rotating in a 0
>    > bit instead of the c-bit, or possibly the c-bit is stuck at zero.
>Yup, good suggestion. And that would likely explain why things boot; I can't
>see too many OS's using 'ROLB'!
>	Noel

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