On 1/21/16 9:48 AM, Mark Pizzolato wrote:
Hi Will,
On Thursday, January 21, 2016 at 7:01 AM, Will Senn wrote:
A quick couple of questions...
1. Why does SimH prompt to overwrite the last track on some images every
time it runs, even if I let it, it will ask on the next run.
2. What is a use case for setting bad blocks and is it a one shot deal or does
it
need to stay in the .ini?
DEC shipped disk devices which were formatted at the factory. Almost all
disk media had a very small percentage of the media which didn't perfectly
store data. Certain modern, disk devices (MSCP) had spare sectors built into
the internal format information on the drives and they presented a full disk
of clean blocks to the system. Older disks shipped with factory with a defect
table written in the last track of the device. When an operating system
initially wrote file system data structures on a disk volume, it would allocate
the defective sectors to a BADBLOCK file on the disk and therefore those
sectors would be avoided for normal user data. During the life of the disk
some areas might subsequently become bad. If the OS detected these
later the newly identified areas would also be allocated to the BADBLOCK
disk file and the rest of the disk could still be used.
Thanks for the explanation.
So, back to your original question. The prompt about "overwriting the last
track" is intended to create an essentially empty list of defective sectors
for a newly created disk image (for the disk types which actually had this
'feature'). The intention is that you should be prompted for this (or could
provide a -Y switch on the attach command) ONLY when you are creating
a new disk image. If you are being prompted with this question each
time you attach an existing disk image then there could be a bug. Please
identify the simulator and the specific commands which generate this
prompt.
OK. I figured some of this out...
In RT-11v5.3 if I have the following ini section for a disk:
set rl1 writeenabled
attach rl1 storage.dsk
And I say no initially to the prompt:
Overwrite last track? [N]N
When I try to initialize the disk in RT-11, I get an error:
.initialize dl1:
DL1:/Initialize; Are you sure? Y
?DUP-F-Bad block in system area DL1:
But, if I answer Y:
Overwrite last track? [N]Y
All is good in the world. I get no errors initializing and I no longer
get prompted at startup:
.initialize dl1:
DL1:/Initialize; Are you sure? Y
.dir vol:
0 Files, 0 Blocks
10172 Free blocks
This being the case, it appears that set badblock does not appear to be
required. For the sake of discussion, if there is a case when it is
required, is it a one-shot deal where the command is run in simh and
then left out of the ini file after the bad block is created?
Thanks,
Will
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