[vcf-midatlantic] LSI-11 simulator

Herb Johnson hjohnson at retrotechnology.info
Thu Sep 10 12:23:59 EDT 2020

> 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?


>  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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