Re: Did Commodore cheat with the quad density floppies?

Den Sat, 5 Jan 2019 20:15:16 -0500 skrev "Mike Stein"
<mhs.stein@gmail.com>:
> 
> ----- Original Message ----- 
> From: "Mia Magnusson" <mia@plea.se>
> To: <cbm-hackers@musoftware.de>
> Sent: Saturday, January 05, 2019 4:52 PM
> Subject: Re: Did Commodore cheat with the quad density floppies?
> 
> 
> > ...It also requires heads able to handle the flux transitions per
> > distance rate, which in the 1001/8050/8520 is probably solved by
> > using heads
> that were really intended for the HD MFM format.
> 
> Were HD disks/drives around when the 8050 was released? It looks like
> the 8050 was around in 1980 or earlier, whereas HD drives didn't
> really appear until 1984; when I bought my first new 8050 for $2500
> it had a greater capacity per disk than most contemporary systems..

Good point. Maybe the 8050 were one of the first drives to have a
smaller head gap than most DD drives did?
 
> More likely that they were just 'standard' DD 96/100TPI heads; the
> normal unformatted capacity of 96 and 100 TPI drives was 500KB/side,
> so I'd think that the additional sectors gained by zone recording
> would easily reach the 8050's formatted 500KB on the same DD or 'QD'
> disks.

Were the heads of the DD drives back then good enough?

If so, I assume that the standard drive electronics had some kind of
low pass filter to make the signal/noise level the best possible while
having exactly the required bandwidth for the more common data rate.

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