Weekly Classic Computer Trivia Question (20141205)

Doug Ingraham dpi at dustyoldcomputers.com
Tue Dec 9 10:38:28 CST 2014

Oh my!  I never expected to kindle a flame war (maybe it is rekindle).

My favorite answer is "All of them."  If you assume a terrabyte is
1000000000000 bytes which is 10^12 and the smallest you could expect such a
drive to be.  And also assume a DECtape (not DECtape II) has an unformatted
capacity of 2700000 bits which is 337500 bytes.  So smallest drive capacity
and largest DECtape capacity would give at least 2962962 DECtapes.  Larger
drives and smaller capacity tapes only increase this value.  We know that
DECtapes used by OS/8 have usable capacity of 283008 bytes.  In that case
it would be 3533469 tapes.      It is unlikely that even 2.9 million tapes
were manufactured.

As for physically stacking tapes on a drive, I suppose you could rig up a
platform that could hold tapes up to the point where the drive was
crushed.  I would weigh a reel if I was writing this at home.  I will
estimate a reel weighs 4 ounces.  That means the 2.9 million tapes would
weigh 725000 lbs or 362 tons.

A reel has 260 ft of tape so to wrap around the earth at the equator would
only require 505682 tapes.

I will see if my next trivia question can avoid a minor flame fest even
though they are fun to watch from time to time.

Doug Ingraham

On Fri, Dec 5, 2014 at 9:59 AM, Doug Ingraham <dpi at dustyoldcomputers.com>

> I have had my PDP-8 (no letter) since around 1985.  As part of the deal I
> got a little over 200 DECtapes.  Most of these are SCOTCH 3M branded in
> cardboard boxes and not DEC branded DECtapes in the clear blue plastic
> containers.  I have been thinking about moving this data to a permanent
> storage location so I wondered how much space this would require.   Turns
> out to be about 57 million bytes and that would be without bothering to do
> any compression.
> The trivia question is:
> Approximately how many DECtapes will fit on a single one terabyte drive?
> As there are several possible answers to this feel free to reply on the
> list.  I will give my answer in a few days.
> Doug Ingraham

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