🚀 go-pugleaf

zatar@dadstoy.gbdata.com (Terry Stockdale) writes:

>In <1993Jan7.025054.721@mlb.semi.harris.com> sonny@charybdis.harris-atd.com (Bob Davis) writes:
>>>richk@grebyn.com (Richard Krehbiel) writes:
>>>
>>>>What feature is it that makes the DC2120 tape store 120M on a Jumbo
>>>>250 and only 60M on a Jumbo 120?  Does QIC-80 have twice as many
>>
>>	Isn't the only difference between the Jumbo 250 and the
>>Jumbo 120 that the 250 employs on-the-fly data compression algorithms
>>(sorta like Stacker) to squeeze roughly twice as much data (on the average)
>>onto the tape as the 120?
>>
>>	Aren't the on-tape capacities and recording hardware the same?
>>Just that software (firmware?) has squeezed the redundancy from the
>>data presented to the 250?
>>

>I'm sure they both do.  I have a Jumbo 120 drive.  It gets 60megs on a
>DC2120 tape without compression and "up to 120megs" with the compression
>included in the jumbo software.  The software for the 120 and 250 are 
>the same.  However, I get effective compression on my game drive of
>about 1.1:1, rather than 2:1, and about 1.4:1 on my other drive.  I've
>never seen anything like a 2:1 average compression out of my drive.

>>	Are OS/2 drivers yet available for the Jumbos?

>Nope, and yes.  Colorado will sell you Sytos (sp?) software for $99 to
>support OS/2 2.0.  You can find more info on comp.os.os2.misc, where
>it's discussed rather often.  I do not run OS/2 2.0, YET, until I upgrade
>to a larger hard drive (last weekend, I upgraded a 386sx-16 motherboard
>to a 486DX-33).  The lack of Colorado support for OS/2 was also prominent
>in my reluctance to convert.  I've become a win3.1 user, for lack of tape
>support.
>--

>-- 
>__
>"Even if you're on the right track, 
>you'll get run over if you don't move."  --Will Rogers.

>terry@dadstoy.gbdata.com	Terry Stockdale		Houston, Texas
2120 only identifies the physical tape. The two different drives
format it in different ways. The 120 formats it in accordance with the
QIC40 standard, the 250 as QIC80. QIC 80 has about 50% more tracks and
about a 50% higher bit density on the track: I don't have the exact
figures here, but the resulting product doubles the total bits you can
put on the tape.
The 250 can READ a QIC40 tape so it is supposed to be able to recover
from dumps done with a 120: I haven't tried that. It does not format
QIC40 and I does not claim to be able to write to QIC40 even if
previously formatted elsewhere.

Thus there is a 2 to 1 difference in the number of bits you can store
with the 250. The software, or the optional compressing hardware, does
compression in either case. I have put over 200 MB of "realworld" data
on a QIC80 formatted 2120 in a Jumbo 250, although the number of bits
it can store is only about 120MB.

Bob Wilson
wilson@math.wisc.edu