RX01 Floppies

Johnny Billquist bqt at update.uu.se
Sat Nov 22 00:14:06 CST 2014

On 2014-11-21 19:48, Jerome H. Fine wrote:
>  >Michael Thompson wrote:
>> Where can I get RX01 SSSD 8" floppies?
>> Used are fine.
> I should have realized that the situation needs to be clarified:
> (a)  As far as I know, (almost?) all soft sectored 8" floppy media
> are formatted as either single-density (which is the IBM standard -
> also known as the DEC RX01 option) or double-density.(which
> is the additional DEC RX02 option).  In the latter case, the format
> is essentially the same, but only the data portion of the sector is
> double-density.  In addition, while a DEC RX01 drive can use only
> single-density media, a DEC RX02 drive can use BOTH single-
> density (SSSD) AND double-density (SSDD) media which means
> that the DEC RX02 drive can read / write media from a DEC RX01
> drive - but can boot an RX01 media only if the boot block is first
> changed from DX to DY.

Incorrect. The RX02 cannot read standard 8" Double Density floppies. It 
can only deal with single density floppies, just like the RX01.
The RX02 can deal with both RX01 and RX02 media. However, the software 
(obviously) needs to know how to deal with it, as RX02 media gives you 
256 bytes per sector, while RX01 media gives you 128 bytes per sector, 
which is a significant difference that needs to be dealt with.
(And yes, the software can detect what format each sector is in.)


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