Sector Interleave

Johnny Billquist bqt at
Tue Dec 1 12:11:19 CST 2015

On 2015-12-01 19:04, Johnny Billquist wrote:
> On 2015-12-01 18:09, Paul Koning wrote:
>> I suppose it's possible to do something like interleaving where
>> consecutive sector addresses are not physically adjacent on the
>> media.  Come to think of it, that's exactly what the MSCP RX50
>> controllers do, since MSCP implements the mapping from LBA to physical
>> addresses in the controller, not the host.  But in older systems where
>> the controllers handle physical addresses and the mapping from LBA is
>> in the driver, interleave is handled there (or above).
> Yes, the "hardware" interleave is what I was assuming everyone here was
> talking about. Otherwise there is no point/need to format to get the
> interleaving... With disks, this is perfectly doable, as the block
> number is in the block header, and the drive/controller scans headers
> until the current block passes by. There is no real reason to actually
> place the disk blocks in consecutive physical order on the disk. Any
> order will work. That's what soft sectors gets you.

To point it out more clearly, in case this seems muddled. The hardware 
interlaving done by MSCP for the RX50 do not really have anything to do 
with MSCP and the ability to map blocks around.

When the floppies are formatted, the sector numbers are written in the 
header of each sector. All later operations always search for the 
correct sector by checking the sector header. As such, this not only 
works on MSCP controllers, but any floppy, on any floppy controller.

And in theory also on pretty much any other kind of disk as well. The 
trick is the ability to format the disk and write the header. For most 
disks you cannot do that yourself.


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