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pearce_jj
August 17th, 2011, 04:44 AM
Hi, I just wondered what this meant, for example then Tandom TM100(-1/-2) service manual (http://vintage-blog.peacon.co.uk/downloads/manuals/tandom/Tandon_TM100-1_TM100-2_Service_Manual_Scan.pdf) says,

"Internal Trim Erase - The drive provides the cntrol signals necessary for proper trim erasure of data."

Thanks!

Chuck(G)
August 17th, 2011, 07:31 AM
Sometimes also called "tunnel erase".

A floppy drive head, when writing, produces "fringe" magnetization on either side of a track that can interfere in reading adjacent tracks, particularly if the radial alignment of another drive is a little off. Trim/tunnel erase creates a small "dead zone" on either side of the track to provide "quiet" guard bands around each track. You can see these bands if you use a magnetic developer to look at a recorded disk.

A floppy drive doesn't really "erase" data in the same sense that an audio tape recorder does. Since it operates at magnetic saturation, it over-writes anything previously recorded.

pearce_jj
August 17th, 2011, 07:42 AM
Thanks very much - so is there a connection between this and the use of 'trim' w.r.t. SSDs? And perhaps more on-topic, is there a downside to using trim erase..., i.e. why was this not the default (or was it)?

Thanks!

Chuck(G)
August 17th, 2011, 08:10 AM
"Tunnel erase" has been SOP for floppy disks for a very long time. It's simply not mentioned in literature because of that.

Heh, I've never thought about it, but there is a dual overlap in terminology with flash/SSD that has nothing in common between the technologies.

"TRIM" (caps) in SSD in the Microsoft world refers to the process of continuously reorganizing the data on an SSD,. There's been a lot of discussion lately in the data forensics world about this making life impossible for investigators. But nothing to do with floppy disks.

"Tunnel erase" also exists in the flash world, but has nothing to do with the floppy term. Here it refers to the erase mechanism--electron tunneling--in flash memory cells.

pearce_jj
August 17th, 2011, 10:58 AM
Thanks, yes I was really just wondering whether the naming of the ATA command "trim" had some historic connection to the floppy process being described here. In effect, whether a disk erase command has always been referred to as trim because of the floppy issue that I now know about, thanks to your 1st reply!

Chuck(G)
August 17th, 2011, 12:06 PM
In the non-MS ATA command world, TRIM just "trims" away the dead meat from a SSD--i.e. discards marginal blocks from the allocation pool.

GADFRAN
August 17th, 2011, 05:05 PM
Again, Chuck comes to the rescue !

Sincere thanks Chuck for all you do - much appreciated by many !

Frank

Chuck(G)
August 17th, 2011, 07:25 PM
My pleasure.

pearce_jj
August 18th, 2011, 11:07 AM
Thanks very much for the replies on this one!