Re: easy project? IBM Microdrive

[mjmahon@aol.com (Michael J. Mahon)]

Chris Morse wrote:

>On Thu, 12 Feb 2004 03:38:59 GMT, Mike Spurgeon <mike@spurgeon.net>
>wrote:
>
>>Michael J. Mahon wrote:
>>> Ed Eastman asked:
>>> 
>>> 
>>>>But how do you interface it to an Apple II?
>>> 
>>> 
>>> Presumably, by using a CFFA card.
>>
>>That would have been my answer.  First one out there that tries 
>>it, report back.
>>
>>For $44 at Pricewatch (Consumer Depot - including shipping), 
>>someone will/should.
>>
>>http://www.pricewatch.com/
>>
>>follow the bouncing ball thru storage/hard drives
>
>Not to sound "negative" about it, but why use a microdrive when you
>can use a compact flash card?  A CF card has no moving parts and would
>long out-live a microdrive.  Yeah, the Compact Flash option is a
>little more expensive right now.. 340MB IBM Microdrive for $44 -vs-
>256MB Viking CF Card for $40, or 512MB CF Card for $102.
>
>Personally, I would go with the "no moving parts" method.. And no
>adapters needed with the Apple II CFFA card.

This brings this tread full circle!

The discussion started with a concern about the long-term write
endurance of CF cards used as primary "hard disks".

Even with wear levelling, and with the 100,000-class re-write
endurance of newer CF cards, there remains some concern about
the practical lifetime of these devices when used daily in a high-
update environment, like software development.

There is less concern in a write-seldom environment, such as
might exist if a CF card is used primarily to play games, for
example.

It is entirely possible that the endurance is now at a level such
that the practical life of a CF card hosting a ProDOS file system
(with its frequent bitmap block updates) is many years, even in
a high-write environment.  What we are missing (so far) is the
data that would allow one to conclude that that is true.

CF cards are used almost entirely as re-writeable storage for
digital cameras and PDAs, where they are re-written about
as frequently as rechargeable batteries are recharged.  Most
use the FAT file system, which has similar FAT-update issues
to ProDOS's bitmap.

Further, some FAT filesystems cache the FAT, so that bursts
of updates to the same few blocks are coalesced and written
only once after a second or so of inactivity.  (ProDOS may have
similar write-coalescing behavior--does anyone know?)

Other FAT implementations simply re-write the FAT blocks
whenever a cluster is allocated or deallocated, resulting in
a high concentration of re-writes on a few blocks.  The wear
levelling algorithms in most CF cards seem to work OK for
this case, at least in typical digital camera usage, but there
are reports of CF cards becoming unusable in cameras after
heavy use...

To summarize, CF is clearly sufficiently rewriteable to be of
great utility in many applications, but the jury is still out on
how long a CF card can be expected to last in an update-heavy
envoronment with an access-concentrating file system, even
with wear levelling.  Actual usage data is needed before CF
can be considered to be longer-lived than magnetic disks,
even allowing for moving parts.

-michael

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