RL02-USB Controller Status/Problem

[Johnny Billquist]

On 2015-04-07 19:21, Pete Turnbull wrote:
> On 07/04/2015 16:25, Paul Koning wrote:
>>> On Apr 7, 2015, at 8:41 AM, Pete Turnbull
>>> <pete at dunnington.plus.com> wrote:
>
>>> DEC does it by having the driver software remap sectors.
>>
>> No, DEC does not do that.  At least not in RSX, as Johnny described,
>> nor in RSTS.
>
> I worded it poorly.  The driver provides the data to remap blocks, but
> doesn't necessarily use a replacement when it gets an error.  As I wrote
> elsewhere, there are two mechanisms: the files called FILE.BAD being
> analogous to the file BADBLK.SYS in RSX, and the bad block substitution
> table in the home block which is used when you perform normal file
> operations - and which only exists for devices such as RL01/02 and
> RK06/07, and is stored in the driver's memory-resident tables.  I don't
> know in detail how substitution happens, but in RT-11, it does.

This sounds identical to how OS/8 does it. It essentially treats the RL 
disks as have a few less blocks than they have. And then the actual 
block numbers are contiguous, but any bad blocks are skipped over in the 
device driver. So at the file system level, it appears as if the device 
have no bad blocks.

	Johnny