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Author Topic: Amiga floppies size  (Read 4649 times)

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Offline danbeaver

Re: Amiga floppies size
« on: April 30, 2015, 07:06:13 AM »
Huh?
 

Offline danbeaver

Re: Amiga floppies size
« Reply #1 on: April 30, 2015, 08:18:39 AM »
OFS vs FFS?
 

Offline danbeaver

Re: Amiga floppies size
« Reply #2 on: April 30, 2015, 08:56:09 AM »
The standard DD floppy can store 1 MB of data.  This is the total amount of bits that can reside on the disk if you were to just run numbers out to it; then you could read 1 MB back as one (1) big hunk of data.  Then again, you half step the head and lay data in between a full head step -- this is not stable, but data lays here as a residual of the full tracks laid down -- a way for a freshly formatted disk to have it's prior content discovered; useful for the 3 letter anal orifice types like the TSA, FBI, NSA, and your MOM.  But let us say we wanted to put files on the disks, then we need to store the names of the files, where they were stored by track, sector, byte, etc.  So in addition to the names, we now needs a map of the disk or BAM, that tells where each file has its data.  Now what if data was written to shi(tt)y flimsy less that a piece of paper thickness magnetic media; well we might want to store some information to tell us our data is messed up or not, so we need something as simple as a CRC (cyclic redundancy check) that is the same when written as when read.  Well, most of can see that now we have lost a chunk of change from that 1 MB of space.  If we are really anal retentive, the we end up like IBM with 720 KB of space, or we do acid like Steve Jobs and squeak 80 KB more from our Orange Sunshine and get not only a disk that changes speed to keep the same data flowing on the little circles in the middle, as the large suckers at the outside of the disk, or 800 KB.  But instead we are the Amiga run by cools dudes who make up a file system similar to TripOS and call it the Original File System -- we start with a disk layout that with all that great fun stuff above and with some added nonsense that made sense when Mitchy and Joe Pillow were up all night dancing.  But a wee bit later, we grab some amphetamines and realize, "Dude, this is slow and stupid!"  We then think up a better file system and bypass Smarter for Faster; we get better performance, weed out some of the stupid crap, add International modes and Directory caches, and, "Bob's you Uncle!"

Any help?
 

Offline danbeaver

Re: Amiga floppies size
« Reply #3 on: April 30, 2015, 05:08:24 PM »
How good is the error correction and subfolder (directory within directory) support?  Is it supported by DiskSalv?  How does the speed of access to a file compare to FFS? Can it be used on other devices, like Catweasel?  Does it ramp up to HD floppies?  Or is it a pebble on the superhighway of computing, best left squished between the treads of a tire belonging to a Dodge 1968 Super Bee heading for that curve in the road that it will never make?
 

Offline danbeaver

Re: Amiga floppies size
« Reply #4 on: April 30, 2015, 06:35:25 PM »
Dude,

An obscure file sysrem needs an obscure metaphor!
 

Offline danbeaver

Re: Amiga floppies size
« Reply #5 on: April 30, 2015, 08:56:39 PM »
I suppose the sarcasm got missed, much as the forest by the trees?
 

Offline danbeaver

Re: Amiga floppies size
« Reply #6 on: May 01, 2015, 02:29:39 AM »
Quote from: paul1981;788662
Was it diskspare also that enabled HD floppies to be formatted to 1.9MB? Or am I getting my devices mixed up?

I remember using this to achieve 1.1MB capacity on my A1200 IIRC:
http://aminet.net/package/docs/hard/HiDensity

At least I think it was that. Oh, also, is it 'floppy's' or 'floppies' anyone?
GCR encoding differs from MFM and was used on the PET/C64 floppy drives.  There are advantages of MFM over GCR, but you can google that if interested.
 

Offline danbeaver

Re: Amiga floppies size
« Reply #7 on: May 01, 2015, 04:08:20 AM »
The Aminet reference for the HiDensity.lha is a bit odd; when I read the file's "readme" it takes into account that the early AT A1200's shipped with a HD floppy drive that could take some advantage of a HD floppy by using, what I assume from the device name, is a GCR format to give a boost on a 2 MB unformatted floppy a storage capacity of 1.1 MB.

Not exactly a plot for a Soap Opera on prime time TV, but a side note into more obscurity...
 

Offline danbeaver

Re: Amiga floppies size
« Reply #8 on: May 01, 2015, 09:32:12 AM »
Quote from: gertsy;788680
How could one not prefer a full head step over a half head step.
Double your capacity, Double your error rate, or was that Double Mint Gum?
 

Offline danbeaver

Re: Amiga floppies size
« Reply #9 on: May 01, 2015, 02:28:06 PM »
Perhaps because it was "ironical"