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Can you use SSDD floppys on a Model III?

Sure. SS or DS had little to do with the ability for a disk to be used on both sides, in practice. The bit to pay attention to is DD vs.HD.
 
Err, weren't the original Model III drives single sided double density?

Now, if you are planning on using the opposite side of disk labeled for single sided use, take a look at it. Some early disks had voids or other issues with the coating on the side not intended for use. I believe 90%+ of single sided disks were perfect for double sided usage when manufactured.
 
Standard TRS-80 model IIIs used single sided 48tpi drives. So single sided double density media is what one would expect to use with it. Of course one may use double sided double density disks, but only utilizing one side unless the disk is "flippy" with an extra index hole. Single or double sided single density will often work, but is not recommended. High density disks will not work.
 
Ah, okay. Wasn't sure if drives that came with them were 180k or 360k, but 360k made more sense to me.

Thanks for the help guys!
 
In actual practice, "single sided" floppy disks are actually fine to use as double-sided, because different systems with single-sided drives had the read/write head on either the top or bottom.
 
Bottom line: Labeling on a 5.25" floppy doesn't mean much, so long as you observe the sectoring (hard or soft) and high-density vs. double/single-density (coating characteristics). I've got disks labeled 100 tpi and 96 tpi--they're the same.

The rest only matters if you're buying pre-formatted floppies. 8" floppies have index apertures in different places, depending on SS or DS, but even those can be remedied with re-punching.
 
Chuck(G) said:
Why not? I wasn't aware that there was any substantive difference. The maximum number of flux transitions per linear unit is the same. It's the encoding that's different.
Click to expand...
I was just thinking from the perspective of what one can find on eBay. DSDD 5.25" would be more common, more new old stock, and less likely to have been through the ringer. No need to specifically look for SSDD or SSSD.
 
As I said, from an electrical/signal standpoint, there's no difference between SD and DD labeled floppies in the 5.25" size. FM recording will exhibit a spectrum with peaks at 1t and 2t; MFM will exhibit peaks at 1t, 1.5t and 2t. Note that the lowest and highest frequencies are exactly the same. GCR similarly exhibits multiple peaks. SD tends to be a bit more tolerant of ISV, that's all.
 
I've never, ever seen a difference in oxide coatings on SS vs DS disks (i.e. only coated on side) - has anyone here? Any photographic evidence?
 
None whatsoever. My contact at Dysan (remember them?) told me that cookies that failed verification tests were flipped accordingly and labeled as single-sided. However, few people even ran across the any flaws in actual practice on either side. After awhile, it no longer paid to distinguish SS from DS cookies as the reject rate had plummeted, so media so labeled were pretty much the same.
 
One of the Commerce Department investigations into imported floppy disks provides a slight window as to the quality of disks produced in the mid-80s. The exact failure rates are redacted but one unnamed company claims a failure rate of 1 in 2,000 disks while others reported closer to 1 in 10 failing with another 30% being listed as marginal (working but not quite meeting ANSI standard).

I have seen a few floppy disks that had gaps in the coverage of coating on the side not intended to be used. Not since 1980 mind.

While not a floppy disk (obviously), SyQuest 135MB disks were built using platters that failed to get both sides correctly covered. So the problem of coating a disk remained tricky for many years.
 
vwestlife said:
In actual practice, "single sided" floppy disks are actually fine to use as double-sided, because different systems with single-sided drives had the read/write head on either the top or bottom.
Click to expand...

This is a myth... There is no single sided drive that used a top head instead of a bottom one. I have repaired dozens of models from the earliest Shugart, Mitsumi, Alps, Texas Peripherals, etc.... There are absolutely none. It would make no sense to have designed one that way.
 
rittwage said:
This is a myth... There is no single sided drive that used a top head instead of a bottom one. I have repaired dozens of models from the earliest Shugart, Mitsumi, Alps, Texas Peripherals, etc.... There are absolutely none. It would make no sense to have designed one that way.
Click to expand...

I guess you never used a DEC RX-50. I think there was at least one other single sided drive that wrote to the upper surface but I can't remember the model.
 
vwestlife said:
In actual practice, "single sided" floppy disks are actually fine to use as double-sided, because different systems with single-sided drives had the read/write head on either the top or bottom.
Click to expand...

rittwage said:
This is a myth... There is no single sided drive that used a top head instead of a bottom one. I have repaired dozens of models from the earliest Shugart, Mitsumi, Alps, Texas Peripherals, etc.... There are absolutely none.
Click to expand...

krebizfan said:
I guess you never used a DEC RX-50. I think there was at least one other single sided drive that wrote to the upper surface but I can't remember the model.
Click to expand...

It's true that the lower drive of an RX-50 (which is a two-drive unit) writes to the "upper surface" of the disk, but that's canceled out by the fact that you stick the disk in upside down. (See pages 6-3 to 6-5 in the Rainbow 100 Technical Manual.)

The important thing is that all single-sided 5.25" drives use the same side of the disk, and therefore if a factory discovered a disk was bad, but only on one side, it could sell it as a "single sided disk" and it would work in any single-sided drive.

The side all the single-sided drives use is the opposite of the label side, where the "label side" is the one that has the write protect notch and index hole on the right side, if you've oriented the disk so that the head aperture (the exposed section of the disk) is at the bottom.
 
krebizfan said:
I guess you never used a DEC RX-50. I think there was at least one other single sided drive that wrote to the upper surface but I can't remember the model.
Click to expand...

Yes, this is a curious design that was apparently made to share the same spindle motor. However, as mentioned, it is still designed to record on the bottom of the disk as you are to insert disks upside down on the bottom drive.
 
We used to punch extra write protect and sector holes in the floppy jacket and you would have a 'flippy' disk. You could take it out and and flip it over and use the other side on a single sided drive.
 
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