R.S. wrote:
Robert Pelletier wrote:
Hi All. Question. Would anyone know the BPI of a 3480 cart running on
3480E drive (mock 3490). We have a request from a user to send us a
38,000 bpi cart. I swear they are 6250 bpi. Can anyone clear this up for
me? Where are they getting the 38,000? Thanks once again all.
<off-topic opinion>
Well, I have never bothered about BPI parameter, since IMHO it's
completely irrelevant for the user. Cartridge capacity, mount time,
rewind time are important.
</off-topic opinion>
Back to the question: CST cartridge contains 160m of tape.
Uncompressed capacity in 36-track drive (3490E) is 400MB.
So 400MB/160m gives 25000 B/cm Inch is 2.54 cm, so the BPI is 63500.
CST in 3480 drive has 31750 BPI.
The values above are without compression.
I don't know exact length of tape and exact capacity, maybe it's not
exactly 160m, however it seems the BPI can be approx. 32000. It rather
cannot be 38000.
---------------------------<unsnip>------------------------------
38K BPI is the correct value. Roland, you need to consider preamble and
postamble times, which are covered by inter-block gaps. These gaps allow
bringing the tape up to speed before reading/writing and the stop time
afterward. The design point was 38K BPI and, IMHO, was admirably achieved.
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