Weekly Classic Computer Trivia Question (20141205)

Rich Alderson RichA at LivingComputerMuseum.org
Fri Dec 5 17:21:47 CST 2014

From: Jerome H. Fine
Sent: Friday, December 05, 2014 3:05 PM

>> tony duell wrote:

>>> Approximately how many DECtapes will fit on a single one terabyte drive?

>> All that were ever made?

> If I remember correctly, a TU-58 tape holds 512 blocks of 512 bytes
> or 262,144 bytes in total or 2 ** 18 bytes

Jerome, "DECtape" without a following "II" refers to *real* DECtape, the
3/4" medium used on DEC's 555, TU-55 and TU-56 DECtape drives.  These were
formatted with 578 blocks of 256 18-bit words (even for the PDP-11, which
ignored bits 0 and 1) or 1102 blocks of 129 12-bit words (= 86 18-bit words)
depending on which architecture the drives were connected to.

These were 4" reels, not cassettes.


Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134

mailto:RichA at LivingComputerMuseum.org


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