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Writing a sector copier cart, need some info.

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    Can I just clarify something? I am trying to write some drive density detection routines, and am currently testing on a US Doubler. I have tried reading sector 4 in immediate mode (DSTAT=0), then reading the Percom Block, but the Percom block returned often/always gives a sector size of $80 when I use a Double Density floppy (256 byte sector size). I was reading the above comments as using SIO read immediate mode on sector 4 would ensure that the Percom block was always subsequently returned correctly (on all drives), but does that only apply to the XF551? I know there are some drives that are listed as not honouring/reporting correctly a Percom block when queried (Page 189 of the Altirra Hardware Reference Manual lists the US Doubler as being one of these drives), but I was hoping reading sector 4 with DSTAT=0 would fix this (it appears not to though).


   Is it best to test sector 4 in various densities, and if the density doesn't match the Percom Block, assume you are dealing with a US Doubler/Super Archiver/Indus GT, otherwise the Percom Block can be trusted? I'd like to be able to support all the drives that return an accurate Percom Block, be able to detect drives that don't return an accurate Percom Block, and drives that don't support Percom Blocks at all. 


   Is there a simple way to do it, or is it a combination of:


   - status check to see drive exists

   - get Percom Block to see if drive support Percom Block at all

   - Validate Percom Block by reading sector 4 according to sector size given by Percom Block

   - status check if reading sector 4 in single density is successful to see if drive is enhanced density or not


   Is there anything else I should throw into the mix, or is there a better way of doing this (still not clear on what SIO DSTAT=0 is actually used for)?


    Any help would be appreciated!

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