Which RT-11 for an 11/03

[Paul Koning]

> On Mar 10, 2016, at 8:51 PM, Don North <north at alum.mit.edu> wrote:
> 
>> ...
>> info: boot     unit=0 blk=0x0000 cnt=0x0200
>> info: read     unit=0 sw=0x00 mod=0x00 blk=0x0002 cnt=0x0800
>> info: read     unit=0 sw=0x00 mod=0x00 blk=0x0006 cnt=0x0400
>> info: read     unit=0 sw=0x00 mod=0x00 blk=0x0008 cnt=0x0400
>> info: read     unit=0 sw=0x00 mod=0x00 blk=0x000A cnt=0x0400
>> info: read     unit=0 sw=0x00 mod=0x00 blk=0x000C cnt=0x0400
>> info: read     unit=0 sw=0x00 mod=0x00 blk=0x0134 cnt=0x0A00
>> info: read unit=0 sw=0x00 mod=0x00 blk=0x0085 cnt=0x0132
>> info: read unit=0 sw=0x00 mod=0x00 blk=0x0086 cnt=0x3CC8
>> At this point, the RUN LED goes off and the system halts.  It looks like the boot loader is loading and running the second-level loader on the tape, but something happens after that. Not sure where to go from here.
> 
> These last two read commands look awful suspicious to me. A single logical device block is 512B (or 0x200) so the count
> parameter is 0x200 for one block, 0x400 for two consecutive blocks, etc. 0xA00 is five consecutive blocks.
> 
> However, 0x0132 (306. bytes) is a partial block read, and 0x3CC8 (15560.) is a read of 30.+ blocks. So I would speculate
> that the code went south prior to these two read commands. Just a guess of course as I have never done this particular
> task. But I would guess that the image you are using has been corrupted in the process.

I was wondering too.  But then again, RT11 can do partial sector reads (and even writes).  They go straight from application through the kernel to the driver.  (A partial block write requires the device, or the driver, to zero-fill to the end of the block -- and yes, some applications require that and will break if it isn't done right, as I found out debugging the RC11 driver.)

If memory serves, what you have is part 1 of the boot (1 sector, block 0), part 2 (2 sectors, block 2), then something is looking through the directory (sectors 6 and up) and then the read from block 134 is presumably a file being read (perhaps a program) and the stuff at 85 and 86 is ???

It might be informative to dump the directory from the tape and analyze it to see what files those later reads refer to.

	paul