But Paul's comment is still right on - the controller for both was a 1MHz i8085 and just could not keep up.

I hated both .. its' too bad DEC refused to use QIC. They did eventually use 4mm DAT on an SCSI (and actually OEM'ed the drive from HP it turns out). The 8mm [Exabyte Unit] was from CSS and many of us in UNIX land had them on our Alpha's - Tru64 supports as a 'latent' device - but the politics of the day were TK-50 and TK-70 was the DEC official drive.

It's interesting until DEC sold off the team and DLT to Quantum, it was not very popular except at VMS sites since the Unix world knew that the SCSI driver had full support for the standard devices. To Quantum credit, they redid the controller (put in a 68K IIRC) and life got much better.

But it was always way more expensive than QIC, 4 or 8 mm.

Clem

On Tue, Oct 16, 2018 at 1:23 PM William Pechter <pechter@gmail.com> wrote:

DEC Tape II was the serial driven TU58.
The TK50 was CompacTape or something like that. It was the predecessor of a number of square tapes...

See DLT on Wikipedia https://en.m.wikipedia.org/wiki/Digital_Linear_Tape

Bill

-----Original Message-----
From: Paul Winalski <paul.winalski@gmail.com>
To: Clem Cole <clemc@ccc.com>
Cc: The Eunuchs Hysterical Society <tuhs@tuhs.org>, cctalk@classiccmp.org
Sent: Tue, 16 Oct 2018 13:14
Subject: Re: [TUHS] Ultrix Tape: Block Size?

On 10/15/18, Clem Cole <clemc@ccc.com> wrote:
> #$%^ - they >>weren't<< like DECtape from a reliability standpoint ...
> ᐧ
The original DECtape was extremely reliable. Not so the TK50.
Calling it "DECtape II" was an insult to the original DECtape. The
problem wasn't so much the drive itself, but the controller. In an
effort to reduce costs, DEC used a controller that had insufficient
buffering capability for a streaming, block-replacement tape device
such as the TK50. TK50s were prone to both data-late and overrun
errors.

The block size is almost certainly 512 bytes.

-Paul W.