Substituting DSHD for DSDD disks (or DS2D if you prefer)

[Paul Berger]

On 2015-10-27 10:53 AM, Jerome H. Fine wrote:
> >Paul Berger wrote:
>
>> >On 2015-10-26 11:38 AM, Jules Richardson wrote:
>>
>>> >On 10/24/2015 09:14 PM, Fred Cisin wrote:
>>>
>>>> Are we really running short of "720K" floppies?
>>>
>>> I went around all the local places that I could think of a couple of 
>>> years ago and bought up whatever stock of floppies that I could find 
>>> (and picking sure were slim). Quite a few boxes of 3.5" HD, a few 
>>> boxes of 5.25" DD, but zero 3.5" DD and 5.25" HD.
>>
> With regard to 5 1/4" DD media, a couple of decades ago, I rescued a 
> few hundred
> RX50 type media from a DEC system which I have not had a chance to 
> look at.
> Eventually, they will hopefully be copied at which point they could be 
> made available
> for the postage to send them.  Note that I am in Toronto (M2R 3G3).  
> So please
> send a note if this media is still needed and I will be sure to hold 
> onto the floppies.
> NOTE that all are obviously USED.
>
>>> 3.5" HD media just killed off the use of 3.5" DD and 5.25" HD, I 
>>> suppose. I'm not sure what the reason for my finding a few boxes of 
>>> 5.25" DD was, though - perhaps it was just produced in sufficient 
>>> volume for there to still be a few survivors kicking around.
>>
> I also have a few dozen 5 1/4" HD floppies which are also DEC RX33 media
> along with a few dozen 3.5" HD media which are also DEC RX23 media.
> These RX23 media still be available in reasonable quantities since 
> they were
> probably the last of the floppy media which was widely used when a 
> 3.5" HD
> floppy drive was still a popular item.  NOTE that all are obviously USED.
>
>>> I've never had any luck finding used disks anywhere locally; people 
>>> are a bit too concerned about data theft these days, and all of that 
>>> seems to go straight to landfill.
>>
>> Not long ago I bought a 100 from floppydisk.com for use with my 
>> vintage HP's they where reputed to be used but looked like new to 
>> me.  They seem to work fine, I have not had any fail to format or 
>> fail in use.
>
> I am not interested for myself, but which type of floppy media were they?
>
> I probably have about 500 hundred 8" floppy media some of which
> are already LLF (Low Level Formatted) to the IBM standard of
> SSSD or 488 blocks.  A few have even been LLF with DSDD
> (Double-Sided, Double-Density) even though they have only the
> Single-Sided Index hole since I have a switch on my DSD 880/30
> which supports using an 8" floppy that has the Single-Sided index
> hole as an 8" Double-Sided floppy.  In DEC naming convention,
> a SSSD 8" floppy is an RX01 LLF, a SSDD 8" floppy is an RX02
> LLF and a DSDD 8" floppy is an RX03 LLF.
>
> The DSD 880/30 has a single RX03 floppy drive.  The DPDT switch
> which I installed supports the use of an 8" floppy with the index hole
> in the Single-Sided location to be used and detected by the RX03
> drive as if the index hole was in the Double-Sided position - which
> avoids the need to punch a second pair of holes.
>
> For those individuals who are using RT-11, my DYX.SYS (RX02
> device driver) supports the use of a bounce buffer which is required
> when the user buffer is in Extended Memory above the 256 KB
> boundary.  I have mentioned this in the past, but it seems that no
> one uses the DYX.SYS under RT-11 any more.  In an emergency,
> it is always possible to use DUP to copy the complete floppy media
> to a small 512 KB file on a drive which supports 22-bit user addresses
> which is usually available at least on the system drive for RT-11 to
> be able to run a virtual job that requires low memory overlays.
> Note that this DYX.SYS is not ready for general release since it still
> does not make use of Extended Memory instead of a very large
> buffer in Low Memory.  But in an absolute emergency, it could still
> me made available.
>
> Jerome Fine
The ones I got where the 3.5" DSDD as used in 9122 mod D and S and 
several disk diskette combo machines and also the 9114 HPIL drive. I 
would really like to get a HP 9895 8" drive but they seem to be few and 
far between.

Paul.