> On Mar 7, 2023, at 8:23 PM, Chuck Guzis via cctalk <cctalk@classiccmp.org>
> wrote:
>
> On 3/7/23 17:04, Zane Healy via cctalk wrote:
>> I’m working on a project, and I need to know the age of various tape
>> formats. For example when were 6250bpi 700’ 9-Track tapes or DC600A
>> cartridges introduced? Is there any good resource online that documents
>> this? Wikipedia is of some help, but the older you go, the spottier it is
>
> Strictly speaking out of an orifice, I'd suggest that 9 track tapes in
> NRZI and PE first came around with the IBM 2400 series tapes, GCR with
> the 3400.
Was IBM the first for each of these?
I'm a bit puzzled by "6250 700'" because the reel size has no bearing on the
format. 10 inch reels (1200 feet) were by far the most common but
occasionallly the smaller 600 foot ones would be seen. and in rare cases (the
infamous DEC TS05 comes to mind) 600' was all that they could handle.
> Prior to the S/360, tape drives were largely 7 track and used NRZI in
> 200, 556 and 800 bpi densities (IBM 700 series drives). Of course,
> there are many outliers.
I added the 14-track CDC drives to the Wikipedia article a while ago. And I've
been learning a bit about the oddball 10 track 1/2 inch tapes used on the
Electrologica X1 (and, apparently, on the Eliott (UK) as well). The X1 tape is
unusual in that it's somewhat like DECtape -- it supports random rewriting but
with variable length blocks limited by a size limit set at format time rather
than a single fixed block size.
paul
