Re: Did Commodore cheat with the quad density floppies?

----- Original Message ----- 
From: "Francesco Messineo" <francesco.messineo@gmail.com>
To: <cbm-hackers@musoftware.de>
Sent: Friday, January 04, 2019 4:08 PM
Subject: Re: Did Commodore cheat with the quad density floppies?


> On Fri, Jan 4, 2019 at 8:19 PM <afachat@gmx.de> wrote:
>>
> 
> I never had the luck to have a 100 tpi drive, so I don't know if the
> disks written around 198x are still readable nowadays, but if the
> failed disks have the same percentage of the ones written with 48 tpi
> mechanics, then probably the reliability of the write format was as
> solid as the one used on 48 tpi drives. 

I have several 8050s and have had excellent experience reading old disks from the 80s. AFAIR when I copied about 20 of those hard sector DD diskettes to soft sector ones in order to reuse the HS diskettes I didn't have a single fatal read error.

One of these days I'll archive all my 100TPI diskettes; I'll let you know how it goes ;-)

Is the higher BPI rating of 8" disks that Andre cites perhaps due to the substantially higher linear velocity of the longer tracks and higher RPM? That's certainly true of audio tapes, that higher tape speed yields higher maximum frequency.

I think what we really need is an authoritative answer to what the maximum reliable flux transition rate is for 300 Oersted media, and at what linear speed (and therefore the maximum BPI on a given track); I would imagine that the design of the read/write head would also have an influence on that maximum...

m