Sector Interleave

[Jerry Weiss]

Jerry Weiss
jsw at ieee.org



> On Nov 30, 2015, at 7:12 PM, Johnny Billquist <bqt at update.uu.se> wrote:
> 
> On 2015-12-01 02:06, Jerry Weiss wrote:
>> 
>> 
>> The TU58 was a block addressable using a cassette tape drive famously(?) called DECtape II.   File placement on the two different linear tracks was a necessary art, especially  if you were booting RT11 regularly.  This helped it to stream or not rewind in sensitive places.   The 1:2 interleave was “built-in” to the block formatting (see EK-0TU58-UG-001_TU58_DECtape_II_Users_Guide_Oct78.pdf).
> 
> I wasn't aware that it did any block interleaving. But yes, file placement was extremely important. Are you sure it interleaved blocks?


See page 1-4 "Two tracks, each containing 1024 individually numbered, firmware-interleaved "records." Firmware manipulates 4 records at each operation to form 512-byte blocks"
 
Also figure 1-5.       Not only interwoven, but reversed for bi-directional r/w I believe.


Jerry