DD vs. HD 5.25" Disks for a 1541

Centallica · Post by **Centallica** » Sat Apr 09, 2005 5:22 pm

Hi Group,

I finally found some 5.25" floppy's for my 1541 and upon reading CBM newsgroup on how to format these things and to scratch etc, they say the High density disks I bought 3 boxes of may not work properly on the 1541 and I should get Double Density instead!

What's the groups thoughts and experience on this?

Any help is appreciated,
Brian

Leeeeee · Post by **Leeeeee** » Sat Apr 09, 2005 5:48 pm

You really need DD disks.

Look at it like this, DD is like writing in soft mud with a big stick, if you want to write more data in the same space, like HD, you need thicker mud or it'll run. To write in thicker mud you need a more pointy stick or you won't make your marks deep enough, that's HD. Trying to write in the thick mud, HD disk, with the big stick, DD drive, won't make deep enough marks.

DD - soft mud, big stick.
HD - thick mud, pointy stick.

This also explains why writing DD disks with HD drives sometimes fails, soft mud, pointy stick. The marks are deep enough but the soft mud can flow back and fill them in.

Lee.

Centallica · Post by **Centallica** » Sat Apr 09, 2005 9:05 pm

So what you're saying is that "I'm shit on a fat pointy stick" with these HD disks :>)

Thanks,
Brian

carlsson · Post by **carlsson** » Sun Apr 10, 2005 3:39 pm

You could always try to bury the HD disks in some real mud, and see if they became more or less DD compatible afterwards. A guy in the newsgroup has committed several similar experiments already.

Mike · Post by **Mike** » Mon Apr 11, 2005 3:13 am

Leeeeee wrote:You really need DD disks.
[...]
DD - soft mud, big stick.
HD - thick mud, pointy stick.
[...]
Lee.

Ah, yes.

I always use the picture of a row of water buckets:

DD: big diameter, not very tall, low volume
HD: small diameter, tall, high volume

and this is, what happens when writing the wrong media

HD head on DD discs -> spills into nearby buckets.
DD head on HD discs -> doesn't fill buckets enough.

even reading a HD disc written as DD in a HD drive can cause problems in a DD drive, as DD heads can't handle the high stored volumes in the water buckets very well.

Greetings,

Michael "water bucket"

Boray · Post by **Boray** » Mon Apr 11, 2005 4:30 am

All I know is... that I can't even format HD disks on my 1541... So yes, buying HD disks is a waste...

/Anders

carlsson · Post by **carlsson** » Mon Apr 11, 2005 7:03 am

But remember that we're talking about the true 120 (?) tpi HD disks, which on an IBM PC formats to 1.2 MB. Some people call the 96 tpi DD disks for high or quad density, and those are a completely different beast and should be much more or completely backwards compatible with 48 tpi DD disks. The 96 tpi ones are much more uncommon though, so it is not likely that Brian found three boxes of those.

Schema · Post by **Schema** » Tue Apr 12, 2005 7:51 am

Hi Brian,

Next time you're in Toronto, stop by this place. They sell the Double Density disks you need. This is where I get mine.

Above All Electronic Surplus
590 Bloor West (just west of Bathurst)
Toronto, ON
416-588-8119

Post by **Jeff-20** » Tue Apr 12, 2005 10:23 am

Is there a way to identify HD from DD by eye? I usually find DD disks boxed and new at thrift stores. I snatch them up.

But recently I found a stack of color disks without sleeves, without stickers. I got them, and I hope they are DD. And where would I go to get sleevevs for 5.25 disks?

By the way, check out this unusual site:
http://www.cyberden.com/cgi-bin/showsle ... SLEEVE=ALL

Schema · Post by **Schema** » Tue Apr 12, 2005 10:55 am

I've heard that you can tell the difference by looking "through" the disk media itself at a light source in the background. If you can sort of see through it, it's HD, if it's opaque, it's DD. But this hasn't worked reliabily for me.

Post by **bbell** » Tue Apr 12, 2005 11:24 am

I have found the HD floppies tend to have a near black surface (very dark grey) and its shiny and very uniform, where DD tend to be a brown or lighter gray colour, and the surface is less uniform (you see streaks on it).

Also the centre hubs are often reinforced on DD and not HD.

Of course the best (destructive way) is "N0:testing,dd"

Centallica · Post by **Centallica** » Tue Apr 12, 2005 12:24 pm

Schema wrote:Hi Brian,

Next time you're in Toronto, stop by this place. They sell the Double Density disks you need. This is where I get mine.

Above All Electronic Surplus
590 Bloor West (just west of Bathurst)
Toronto, ON
416-588-8119

Hi Schema,

I took your advice from a previous email and this is where I got them from (the last 3 boxes) they also had some blue coloured ones in plastic bags with no info to tell what they were...otherwise this is it! I guess I'll have to pick some up from Ebay (unless you wanna trade 3 HD for 3 DD boxes

)

I got my XM1541 cable now and ready to write with this minor hiccup in the way

Frisbee anyone?
Brian

carlsson · Post by **carlsson** » Tue Apr 12, 2005 2:19 pm

Build a Commodore-compatible 5.25" HD drive!

Maybe it has been done already?

Post by **Jeff-20** » Tue Apr 12, 2005 11:09 pm

Do you think one could easily build a 1541 Hard drive?

carlsson · Post by **carlsson** » Wed Apr 13, 2005 3:47 am

I suppose the mechanism is not magical, but one would have to supply some firmware how to run the mechanism. I'm much too unexperienced in those matters though; someone else on this forum can probably explain it better. The thing is how to emulate the DD disk structure; if a HD disk should be divided into six (or eight?) DD disk sides and each side is accessed as an own unit on the same device: LOAD"5:FILE",8

How does the 1581, or for that matter CMD FD-2000 (3.25") do it? Would the interior of the latter be any help for making a 5.25" HD floppy, or are the two different mechanisms normally handled separately by a PC controller?

However, easier to locate good 5.25" DD disks than building your own disk drive, I think. If you take the hassle to build something yourself, I would try the BYO 3.5" disk project by Mika Leinonen:

http://www.students.tut.fi/%7eleinone3/ ... index.html