Re: Apple II-Or Come on people, It's a 20 year old computer

[pausch@saafNOSPAM.se (Paul Schlyter)]

In article <3987d621.61725482@news>,
Jeff Blakeney <CUTblakeney@home.com> wrote:
 
> On 25 Jul 2000 12:24:07 +0200, pausch@saafNOSPAM.se (Paul Schlyter)
> wrote:
> 
>> On the PC there were utlities to read and write various CP/M disk
>> formats.  Some of the better of those utilities could read a few
>> hundred different CP/M disk formats.  One common CP/M format was
>> always missing among all these utilities though: the Apple CP/M disk
>> format.  This was because of the weird low-level disk format which
>> was used by Apple but nobody else and which was impossible to read on
>> a non-Apple system (unless you added custm hardware just for reading
>> those disks).  Yes, this disk format made sense at an early stage,
>> because floppy disk controller cards became simpler and cheaper, and
>> there was no standardization anyway back then.  But as time passed
>> on, non-standard formats became more awkward.  That's why the Mac
>> changed from the GCR to the MFM low-level disk format: because it was
>> used by everyone else and enabled file transfer to/from alien disk
>> formats with only a software add-on.
> 
> As far as I know, the Mac never used the 720k double-density MFM
> format for its native use.  They supported it only to be able to read
> and write PC disks.  Macs continued to use 800k double-density GCR
> format disks for native use.
> 
> They did, however, adopt the 1.44M high-density MFM format for native
> use for compatibility reasons.
 
Probably true.  I've just noticed that diskettes from more recent Mac
models *are* readable on a PC.  IMO they should have gone MFM already
on the DD diskettes, since 800k disk storage is only marginally
bigger than 720k disk storage, and not worth the loss of compatibility.
 
But I suppose the history matters too.  And at the time of the Apple
II, it made great sense to use GCR, since it provided 100k instead of
60k or 80k of the MFM 5.25" disk formats of those days.  In addition,
by using GCR, you could do with some simple TTL logic, instead of
those MFM disk controller chips which then were quite expensive.
 
However, what once made very good sense won't automatically make good
sense forever.  Today MFM disk controller chips are cheap, and MFM
disks can store just about as much as GCR disks.  So there's no
longer any advantage in using GCR instead of MFM for floppy storage,
but there is a disadvantage: the low-level incompatibility.
 
And today, in the age of ever increasing connectivity, the floppy
diskette may disappear altogether.  The Apple Imac's and their lack
of a floppy reader as standard equipment is an interesting move;
however the Imac was here predated by some PC laptops, which too did
omit a built-in floppy reader to offer it as extra equipment instead.
 
-- 
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