history is hard

Fred Cisin cisin at xenosoft.com
Tue May 26 19:04:10 CDT 2020

>> Fred 
>> ... discusses problems with SMARTDRV (in MS DOS 4.01 and later).

On Tue, 26 May 2020, Christian Groessler via cctalk wrote:
>> I'm not sure if it was technically a form of caching, but the AmigaDOS
>> delayed floppy write (well before MS-DOS cache) caused enormous problems
>> for Amiga users.  (It may well have contributed significantly to the lack
>> of market success.)
>> Basic problem: you save something to a floppy, and pull it out.    You now
>> have a corrupted floppy.  You needed to wait a few seconds for the OS to
>> decide "well, looks like I better flush the last few dirty sectors out to
>> that floppy".
>> (I contend it was a form of write caching, designed to speed writing to
>> floppies where writing tended to occur in nearby places.)

also, the Amiga wrote track rather than sector at a time, so a sector 
write needed to be delayed until the track was ready to be written

> They probably would just have to implement a "sync" command, and tell people 
> to use use it before ejecting a disk...

computer/OS control of disk eject and power is what's needed to solve it.
Either hardware locks, or very thorough (difficult) eductaion of users.
If the user ASKS THE OS to eject the disk, then it can easily be delayed 
until safe to do it.  Similar with power shutdown (which users are now 
familiar with)

In addition, the performance improvement that SMARTDRV did of optimizing 
the sequence of multiple writes out of sequence (all directory sectors, 
THEN all disk sectors) was dangerous if there was an interruption (not 
necessarily just user) before it was finished.

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