Recovering data from 4mm and 8mm tapes

Dave G4UGM dave.g4ugm at
Tue Mar 24 03:32:26 CDT 2015

I read somewhere that manufacturers implemented compression and the schemes were incompatible between drive makers. Perhaps this has caused issues for some..


> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Eric Smith
> Sent: 24 March 2015 08:30
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Recovering data from 4mm and 8mm tapes
> On Mon, Mar 23, 2015 at 9:59 PM,  <healyzh at> wrote:
> > Not every DDS1 drive can read every DDS1 tape.  Not every DDS1 tape
> > can be read in a different specimen of the same model drive as which
> > it was written in.
> I'm not disputing your statement in general, but I've apparently had better
> results with DDS interchange than you have. I've used six DDS1 drives from
> four vendors and three DDS2 drives from two vendors, and didn't have any
> interchange problems until one of the DDS1 drives somehow became
> seriously misaligned. I believe this must have been the result of physical
> trauma causing damage affecting the relative positions of the head drum and
> the tape on the vertical axis (along the width of the tape), or at least with a
> signifcant component on that axis, because the track following servo should
> otherwise be able to compensate for a fair bit of mechanical variation
> between drives.
> When the DAT and DDS formats were designed, it was intended that they be
> robust enough for good interoperation between drives without need for any
> manual alignment of individual drives.
> Eric

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