[CoCo] 720kb vs 1.4mb 3.5" disks

[Gene Heskett]

On Friday 12 December 2003 22:00, John E. Malmberg wrote:
>KnudsenMJ at aol.com wrote:
>>> IT'S WINDOWS that throws the scare on you when
>>> you reboot, because it KNOWS it was not shut down properly, so it
>>> goes through this whole mess of hard drive scanning and file
>>> verifying.
>>
>> Yes, and Linux insists on the same thing if not properly exited. 
>> And that includes using Ctrl-Slt-Delete too.  Only OS-9 is capable
>> of booting right back up after a power-down or reset.
>
>It has to do with how the blocks are allocated on the disk and how
> the directories are populated.  When a file is written, the disk
> must be updated in more than one place at a time.  Usually the
> order is chosen so that if it is interrupted, the operating system
> will have clues to clean it up, and files will not get corrupted. 
> And either the operating system will have to clean it up, or space
> will be lost on the disk.
>
>OpenVMS gives you the option to defer the clean up for a later time,
> but it is still better to do an orderly shutdown.  Except for
> software or hardware upgrades, most of my shutdowns are caused by
> the power going away as I do not have an UPS.
>
>Most of the issues come from operating systems defering updates to
> the disk from having large file cache memory.
>
>The COCO does not have lots of memory to buffer up I/O, so it is
> less likely to have a power interruption at a critical time that
> would leave orphaned space.
>
>If there is not a utility to check the integrity of the OS-9 file
>system, then there should be.

There is, its called dcheck, John.  It basicly looks at the directory 
and file descriptions, compares that with the allocation map, and if 
they don't match, squawks.

>> BTW, every Coco owner knows not to kill power without unclamping
>> any floppies in the drives, right?  I still remember the salesman
>> demonstrating a PC Jr telling me "This is a REAL computer, you
>> don't have to worry about that anymore."

>The only issue I ever heard about that is long term storage of the
>floppies with the heads clamped down was bad.

Thats because the plastic rosette that does the clamping will lose its 
springyness after a while, become loose enough that it no longer 
transfers a good enough grip to rotate the disk.  Such problems were 
very critical for 8" drives, much less so for 5.25 inchers, and 
non-existant for the 3.5's because the disk is pin driven and 
magnetically held to the spindle, a basic design change in how the 
disk is spun.

-- 
Cheers, Gene
AMD K6-III at 500mhz 320M
Athlon1600XP at 1400mhz  512M
99.22% setiathome rank, not too shabby for a WV hillbilly
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by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.