"HardDrive" Images

[+CharlieChaplin]

17 hours ago, Nezgar said:

I always thought of "quad density" as 5.25" DSDD, 40 tracks on each side (80 tracks total), like a double sided XF551 disk as "quad" since it double of a single sided double density disk. But indeed it would also match a single sided 80 track disk, but those were usually not 5.25". 

 

There were 80 tracks (per side, 160 total), DSDD, 96 TPI, 5,25" disks available for a while - the 5,25"  720k disks (also named quad density disks); they were available before the 1.2 meg 5,25" HD disks and a short while after; but the 5,25" HD and especially the 3,5" DD and later 3,5" HD disks drove or threw them off the market. So these 720k / 5,25" disks are as rare as disks with two timing/index holes...

 

There were also some short battles for the next disk size format (after 8" and 5,25"), e.g. 3", 3,25" and 3,5" were available and in the end 3,5" won and many drive manufacturers adopted it after a while and stopped producing 5,25" and other drives.

 

Here is an excerpt from Wikipedia:

https://en.wikipedia.org/wiki/Floppy_disk#5_1⁄4-inch_floppy_disk

(under "Sizes, performance and capacity")

 

5 1⁄4-inch QD		720 KB	720 KB
5 1⁄4-inch RX50 (SSQD)	circa 1982	400 KB	400 KB
5 1⁄4-inch HD	1982[45]	1,200 KB	1.2 MB

 

and also: https://en.wikipedia.org/wiki/List_of_floppy_disk_formats

(under "physical composition")

 

	Single/Double	40	48	5876	300 Oe	250 KB
	Double	80	62.5			(Apple FileWare)
	Quad	77	100		300 Oe	500 KB (Micropolis-compatible)
	Quad	80	96	5922	300 Oe	500 KB
	High	80	96	9646	600 Oe	833 KB

Edited September 22, 2019 by CharlieChaplin

[Jeffrey Worley]

On 9/21/2019 at 2:48 PM, Nezgar said:

I always thought of "quad density" as 5.25" DSDD, 40 tracks on each side (80 tracks total), like a double sided XF551 disk as "quad" since it double of a single sided double density disk. But indeed it would also match a single sided 80 track disk, but those were usually not 5.25". 

I don't recall ever seeing a single-sided 80 track drive either.  I imagine such things exist, but all I've handled have been double-sided.  But Quad is the term we used to denote 80 track double-density, so that's what's familiar to me.  I've never seen the term used in any official document.  I think, quad density would be apt for double-density 80 track, but the number of sides does not modify the density, merely the surfaces, so quad for a double-sided 40 track can't be right.

 

Jeff

[Jeffrey Worley]

1 hour ago, Technoid Mutant said:

I don't recall ever seeing a single-sided 80 track drive either.  I imagine such things exist, but all I've handled have been double-sided.  But Quad is the term we used to denote 80 track double-density, so that's what's familiar to me.  I've never seen the term used in any official document.  I think, quad density would be apt for double-density 80 track, but the number of sides does not modify the density, merely the surfaces, so quad for a double-sided 40 track can't be right.  That would be like calling a double-sided single-density 40 track disk "Double Density".

 

Jeff

 

[+Nezgar]

On 9/27/2019 at 8:24 AM, Technoid Mutant said:

I don't recall ever seeing a single-sided 80 track drive either.  I imagine such things exist, but all I've handled have been double-sided.  But Quad is the term we used to denote 80 track double-density, so that's what's familiar to me.  I've never seen the term used in any official document.  I think, quad density would be apt for double-density 80 track, but the number of sides does not modify the density, merely the surfaces, so quad for a double-sided 40 track can't be right.

Well speak of the devil...

 

[Jeffrey Worley]

3 hours ago, Nezgar said:

Well speak of the devil...

 

Oh, the case for the drive, which is really cool by the way, is not the drive mechanism's model at all.  The drive mechanism will have a sticker on it somewhere indicating that it is a Tandon or a Mitsumi, or a Toshiba, or some major make.  Ohio Scientific shipped just a few of these drives, but the mechanisms were industry standard and made by the hundreds of thousands.  Where they've all gone is a mystery.  Finding 51/4 inch mechs these days is an expensive prospect.  If you want a good home for this one, I'll hang it in my Percom.  ?

 

[mutterminder]

This is a very interesting discussion, for those of use who have lived through the evolution floppy disk storage as I have.  The difference between "single",  "double", "enhanced", "quad", "high", "extended", etc density, was initially used to denote the bit storage density relative to some initial value for a given disk size and track spacing.  For instance,  my first floppy disk drive was a 5.25"", 35 track single sided drive that stored 80k.  One could have used a 40 track drive that stored 90K, but it was the same density in that it stored the same amount of bits per track and the same number of tracks per inch, it just used more of the inner portion of the disk.  Of course the actual physical bit density was higher in the inner tracks but the bit rate of 125Kbs was constant across the tracks. When I upgraded to a double density disk controller, the recorded bit rate per track was doubled to 250Kbs so the disks had "double" the bit density per track.  If we keep all other parameters the same, and double the bit rate again, one would have a "quad" density disk.

 

From this perspective "single", "double", and "quad" all refer to the number of bits per track.  However even drive manufactures couldn't seem to agree on common terminology. If you double the amount of tracks per inch for a given disk size, this too doubles the data density in terms of the number of bits per square inch.  So you could, I guess refer to 125Kbs bit rate, 80 track disk as double density.  But for me,  I always associate density with bit rate.  It's all relative.  The tricky part becomes, "What is it relative to?"

 

Edited December 7, 2019 by mutterminder

[Jeffrey Worley]

9 hours ago, mutterminder said:

This is a very interesting discussion, for those of use who have lived through the evolution floppy disk storage as I have.  The difference between "single",  "double", "enhanced", "quad", "high", "extended", etc density, was initially used to denote the bit storage density relative to some initial value for a given disk size and track spacing.  For instance,  my first floppy disk drive was a 5.25"", 35 track single sided drive that stored 80k.  One could have used a 40 track drive that stored 90K, but it was the same density in that it stored the same amount of bits per track and the same number of tracks per inch, it just used more of the inner portion of the disk.  Of course the actual physical bit density was higher in the inner tracks but the bit rate of 125Kbs was constant across the tracks. When I upgraded to a double density disk controller, the recorded bit rate per track was doubled to 250Kbs so the disks had "double" the bit density per track.  If we keep all other parameters the same, and double the bit rate again, one would have a "quad" density disk.

 

From this perspective "single", "double", and "quad" all refer to the number of bits per track.  However even drive manufactures couldn't seem to agree on common terminology. If you double the amount of tracks per inch for a given disk size, this too doubles the data density in terms of the number of bits per square inch.  So you could, I guess refer to 125Kbs bit rate, 80 track disk as double density.  But for me,  I always associate density with bit rate.  It's all relative.  The tricky part becomes, "What is it relative to?"

 

I think that FM would properly be the point of reference.  FM = single density.  MFM = double density.  The Atari 1050's signature compromise 'enhanced density', or 'density-and-a-half', as it has also been called, is an MFM mode.  As for the others, there are the 8" drives, which are MFM, I think.  Sector sizes might differ, but linear density will reflect the encoding.  For densities higher than 77 track 8', 'High' density covers that -- the 1.2 and 1.44 meg drives.  Certainly, the number of cylinders will increase the storage in a linear manner, but it doesn't change the underlying encoding method and therefore is referred to as a separate characteristic.  This reliably gives you the storage:

 

sssd 40trk fm single -sided (90kbytes (ish))

ssdd 40trk fm double-sided  (180kbytes (ish))

dsdd 40trk mfm double-sided (360kbytes)

 

Sector sizes vary some, but the encoding dictates the realizable storage.  I think, for example, that the 77 track 8" drives use an MFM format that's like the double density version of Atari's Enhanced Density:  MFM 256byte sectors, 26 sectors per track....  This is a considerable increase in linear density and verges on requiring special media.

 

The High density drives, 1.2 and 1.44mb 5.25 and 3.5" drives use different media, different encoding, and higher linear densities than previous 96tpi drives.

On disk boxes and other literature, you will see a reference to 48tpi, 96tpi, and 135tpi.  These refer the number of Tracks Per Inch the media is certified to store.  48tpi is what 40 track and 35 track drives need, and 96tpi disks are for 80 track drives.  135 TPI is, iirc, for 2.88mb formatted disks?  IBM had a late format...?  For 8" 77 track drives, you would use disks so marked.  Some, quite a few, 3.5" high-density drives support "3mode", which makes the drive electronically compatible with an 8" 77 track drive.  A simple wiring adapter and this drive will serve for the larger, more expensive 8" drive.

 

For the Atari 8-bit, if I were setting up for the most flexibility in controlling floppy mechs, I'd recommend:

 

The SWP ATR8000.  Wonderful controller, extremely flexible and powerful, excellent CP/M machine as well.  Hosts RS232, Centronix, and disks for Atari.

 

The Percom AT88 (with doubler board).  This is a flexible and powerful controller able to run most any mech that supports MFM and FM modes.  The roms are frequently older.  The Percom and ATR8000 suffer from those older roms.  They are not self-informing as to all aspects of the media format.  This can result in seeming bad disks.  A program like "Percom" for the command line allows one to manually specify the number of sides and density.  Most drives are pretty good for auto-density, but not for number of sides.  Another useful tool for this that is in everyone's toolkit is included with Spartados X, the "MYDUP" program.  The "O" function of this dup-sys emulator actually works just as the Mydos command does.  So you can set Step rate (very nice also for older drives that have ridiculously slow step rates in rom), density, number of heads, sector size, sectors per track....

 

This is a problem general to the Atari.  Double-sided disks need to be specified as such.  The Mydos function is no accident.

 

And by far the best would be the CSS Black Box Floppy Board.  That thing is bulletproof, will read a piece of paper, copy a chalkboard, read ancient disks, interchange disks flawlessly, operate at speeds that embarasses every other floppy controller for the 8-bit ever, and control high-density drives in their native high-density modes.  Bob Puff is a genius.  It is in all respects density and side 'smart' as well.

 

Thus endeth the diatribe,

 

Jeff

 

 

 

...

 

 

Edited December 8, 2019 by Jeffrey Worley

[mutterminder]

I wouldn't mind having one of those CSS Black boxes with a Floppy Board, but I'm not sure if they are even available any more.  Also, though I enjoy using legacy media, like tapes and floppy disks, the amount of space taken by the media and the hardware required to read it, makes it increasingly less likely that I would really get the full benefit of such a device.  I would likely just use it for copying disk images  for archival preservation. Probably the only thing keeping me using my Atari 8-Bits is the availability of the various flash storage interface devices that are now on the market.

[atarixle]

RespeQt should offer "maxed out volume" (or similar) for creating a 16 MB Image using 256 Bytes per most of the 65535 Sectors (or even 32 MB for SpartaDOS using 512 Bytes per Sector).

Edited December 15, 2019 by atarixle

[flashjazzcat]

33 minutes ago, atarixle said:

RespeQt should offer "maxed out volume" (or similar) for creating a 16 MB Image using 256 Bytes per most of the 65535 Sectors (or even 32 MB for SpartaDOS using 512 Bytes per Sector).

Like this:

 

Edited December 15, 2019 by flashjazzcat

[atarixle]

Of course you can do that, but I meant that it could be one of the defaults/standards/pre-configurated options.