[vcf-midatlantic] LSI-11 simulator

Bill Degnan billdegnan at gmail.com
Thu Sep 10 13:13:36 EDT 2020

PDP11GUI allows you to create bootable media by simulating tape storage via
PC rs232 port.  What I did was use simH to create the boot disk I wanted,
tested to make sure it worked and then used PDP11GUI to dump the image onto
an awaiting RL02 disk.  You can do the same with RK05 and I presume RX01/2
as well.

On Thu, Sep 10, 2020 at 12:25 PM Herb Johnson via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

> > No RT-11 disk image I’ve used will boot,
> > I was hoping someone could point me to a listing of what the on-disk
> boot block code on an RT-11 floppy might look like.
> Rich, I don't understand your problem. If you have access to RT-11 disk
> images on the Web, my guess is some of them are "bootable". By
> "bootable" that means by your account, they have PDP11 boot code on
> their first sector. If they have boot code on their first sector - then
> extract the first sector and *hand disassemble the binary*. Then you
> know what that code quote "looks like".
> 256 words (512 bytes) is just a handful of disassembly work - hardly
> worth bothering to run an emulator to run some debugger to produce some
> PDP-11 code. and you seem so deep into this custom  emulator and the
> LSI-11 architecture, that you seem to know what you'd need to make sense
> of the boot code. I'm familiar with PDP-11's a little, it's not
> horrendous binary code.
> YOu also say, this emulator apparently needs a custom RT-11, presumably
> with custom boot code. But the creator doesn't recall the details. Well,
> 24 years is a long time to remember such things. That being the case,
> you will have to figure out the boot process anyway. You already have to
> dig into the emulator. And you seem to know the hardware. Thus doing the
> hand disassembly will be, er, "informative".
> What am I missing here? Do you need some known bootable RT-11 diskettes,
> so you can put one in some drive and read off the boot sector? Or
> someone to send you that binary or disk image?
> Likewise:
> >  It’s like looking for a disassembly of the MS-DOS boot sector.
> (snort) MS-DOS DEBUG will do that, with a IBM PC tech manual in hand.
> I don't mean to belabor the point, but maybe this is as I suspect: a
> desire to avoid hand-disassembly. If that's a personal issue, my
> apologies, but I think it's a very useful skill. And if it's not a
> desirable task, well, there's usually debuggers which do that, or one
> can cobble up a disassembler in one's favorite language (or borrow one
> and rework it). I've done all those things, and still do, but that's
> just me.
> Puzzled, Herb
> --
> Herbert R. Johnson, New Jersey in the USA
> http://www.retrotechnology.com OR .net
> preserve, recover, restore 1970's computing
> email: hjohnson AT retrotechnology DOT com
> or try later herbjohnson AT retrotechnology DOT info

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