NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/comp/sys/amiga/hardware/13120

Text File | 1992-07-23 | 3.3 KB | 63 lines

Newsgroups: comp.sys.amiga.hardware
Path: sparky!uunet!mcsun!sunic!kth.se!news.kth.se!orre
From: [e-mail] (Roland Orre)
Subject: Re: About to add a SyQuest....
In-Reply-To: [e-mail]'s message of 23 Jul 92 09:28:56 GMT
Message-ID: <[e-mail]>
Sender: [e-mail] (Usenet)
Nntp-Posting-Host: thalamus.sans.kth.se
Reply-To: [e-mail] (Roland Orre)
Organization: Royal Institute of Technology, Stockholm, Sweden
References: <[e-mail]>
    <[e-mail]> <[e-mail]>
Date: Thu, 23 Jul 1992 14:02:21 GMT
Lines: 47

In article <[e-mail]> [e-mail] (Paul Broe) writes:
> In article ... (Roland Orre) writes:
>> A curious fact is that the SyQuest 88 Mb Cartridge is ... i.e, 84Mb.
> I think 88 Mb is the unformatted (raw) capacity. That is usually what the
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> drive manufacturers advertise.
> (My Quantum 105 formats to 100 Mb and The SyQuest 44 Mb drive I have formats
> cartridges to 42 Mb.) Formatted capacity varies somewhat
> from computer to computer.

Considering floppy disks yes, but for SCSI disks not normally. You
don't often speak about the unformatted capacity for a SCSI disk but
in the SyQuest case the unformatted capacity is about 100 Mb. For
floppies the different formatted capacity depends on how much
overhead and how long gaps you put between the sectors.

SCSI disks are normally preformatted from the manufacturer and you
don't often need to low level format these.  And if you do, it is the
built in controller that determines how the physical tracks will be
formatted.  I did low level format one of my SyQuest disks but this
showed to be unnessary. The rest of them I have just quick formatted.

On a SCSI disk the manufacturer has specified how many blocks that will
be visible for the user. These blocks are logical blocks that you can
access in any organization you want. You will split the address space
into cylinders (tracks), heads and number of blocks per track. This
organization need not have anything to do with the physical organization
on the disk.

For maximum utilization of this logical address space you want
tracks * cylinders * sectors/track to be as close to the available
number of blocks as possible. For the Quantum 105 Mb case I could
achieve about 102.5 (if I remember correct) Mb by splitting the
total space into three different partitions with different organization
of tracks and sectors. Often more pain than you gain.

I think that the reminding space may be spare blocks that can be used
for remapping of bad blocks but may also be possible to utilize if you
go beyond the manufacturers recommendations. The possibility to do this
may vary between different prep programs.
--------------------------------+----------------------+-----------------------
Roland Orre                     | O---O---O Studies of |       [e-mail]
Dept. of Computing Science      |  \ /|\ /| Artificial | [e-mail]
Royal Institute of Technology   |   O-O-O-O Neural     |
SANS, NADA, KTH                 |   |/ \ /| Systems    |  Phone: [phone]
S-100 44 Stockholm, Sweden      |   O---O-O            |    Fax: [phone]
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