Pertec Interface Cable Length

Chuck Guzis cclist at
Tue Aug 13 01:35:10 CDT 2019

On 8/12/19 8:16 AM, Nigel Johnson via cctalk wrote:
> Another consideration with the TC02 is the small buffer. I don't know
> what tape speed your drive runs at, but we lost a lot of sales to Dilog
> because of buffer overflow on some of the faster CDC dirves.  When we
> came out with the TC03, it had a larger buffer to handle this.

The Qualstar drive is a *slow* drive. 50 ips in 1600 PE mode and a
whopping 12.5 IPS in 6250 GCR mode.   Transfer rate in either is about
80KB/sec.   Qualstar doesn't have a mechanical buffer (spring arms or
vacuum column) like most drives; it's all handled by the reel servos.
It's wonder that it works at all.    I doubt that it will overwhelm a
PDP11.  It probably doesn't overwhelm an IBM PC XT.   The SCSI version
of the drive does have a 256KB buffer, but I'm uncertain what the Pertec
interface model has.


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