12 Nov
1998
12 Nov
'98
2:22 a.m.
> The basic concept would be to simply sample the
MFM (or RLL) channel
> code at somewhere around 50 MHz as it is being written, and store the
> data on the ATA drive. The interface would keep one track buffered in
> RAM. Whenever the host requests a head change or seek, the buffer would
> be written to the ATA drive (if it is dirty), and reloaded with the data
> for the new track.
> This would require a much larger ATA drive than
the original drive it is
> emulating, 102K bytes per track. To emulate a Maxtor 2190, this requires a 2G
> ATA drive. You could even emulate drives larger than that by emulating more
> cylinders.
This is an intriguing concept. But would it be any
more difficult to
decode the data being written by the MFM controller and written digitally
on the IDE drive to improve efficiency? Would this make reading the data
back difficult?
No, anything you need is just imense CPU power. Recalculate
the bytes from the MFM stream and store it on a different
drive (that must be local, not visible to the Host). And
backwards generate the MFM data from the ATA data. Timing
bit arsh if you want to do it in real time, but since a
local CPU is already usefull for disk (ATA) controll and
conferting (can also be done by hardware) there could
also be some 256 Meg of mem for building/editing the MFM
stream and transmit it later (when ready).
And since w hafe the room of a full or half height drive
available, it could be put in replacement for the original
drive.
Gruss
hans
--
Ich denke, also bin ich, also gut
HRK