[sebhc] H8 Emulator update

[Dave Dunfield]

>>I need to understand how HDOS knows what size the drive is.
>>If you could give me bootable images for 40-track DS, 80-Track SS
>>and 80-track DS, what would help a lot.
>
>All the size info comes from the label sector.   But bootable?  Wouldn't 
>just mountable do?  I made up some blanks in various formats (by hand, I 
>don't actually have a ds, 96-tpi drive) and put them in a new empty-init 
>section under disk-images.   I haven't yet made my fantasy 512-track 
>megafloppy.  :-)
>
>But be aware these images aren't tested themselves.  Maybe Eric's sftool can 
>help confirm their integrity when it's uploaded.

Mounable should be OK - I requested bootable, because if I could boot it I
would be more confident that it's working correctly - I don't really have
much in applications to read/write in HDOS (I suppose I could write a BASIC
program).


>>[I'll bet this is one reason why INIT doesn't work - I don't
>>  currently accept data for sector headers, and would therefore
>>  not return the right volume id after an init - I'll have to
>>  check into this]
>
>No, it never gets that far .. the message "Wrong type of media ...".
>indicates that initial media tests (involving index hole timing) didn't 
>pass.

Could you give me all the gory details of exactly what it is looking for
an exactly how it is performing the timing ... ?

This is likely to be very tricky to emulate in the simulator.
Currently, the simulator is using a "trick" to allow the disk timing to
work for any virtual CPU speed (not counting the software delay loop in
HDOS 2.0) - that is it uses the I/O events to the disk port to adjust the
timing of the virtual disk rotation - it keeps in step with the software
driver's accesses in order to present the right thing at the right time
no matter how fast the VCPU is running - this is likely to break in the
init code if it is doing a separate timing of sector hole index pulses.

Regards,
Dave
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dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Vintage computing equipment collector.
                http://www.parse.com/~ddunfield/museum/index.html

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