Erich Dollansky <er...@alogreentechnologies.com> wrote:
> On Tuesday 21 February 2012 13:06:57 Robert Bonomi wrote:
> > Erich Dollansky <er...@alogreentechnologies.com> wrote:
> > > On Monday 20 February 2012 21:44:43 Da Rock wrote:
> > > > On 02/18/12 17:47, Erich Dollansky wrote:
> > >
> > > > > when I got my hands for the first time on a BSD system, the machine
> > > > > has had several 5MB hard disks.
> > > > >
> > > > > I assume that what now is called partitioning came from the need to
> > > > > have several disks to run a serious system.
> > > > >
> > > > > And yes, it was possible to boot and run BSD with at least 20 users
> > > > > on several 5MB disks.
> > > > >
> > > > > Erich
> > > > Erich, can I be so bold as to ask what brand the disks were? And tax
> > > > your memory as to when?
> > >
> > > it was DEC PDP-11 with a strange drive. One disk was fixed, one was
> > > removable.
> > > This is the reason why it was easy to switch the operating system. RL ..
> > > something like this was the disk name.
> >
> > AHA. probably an 'RL-05', cousin to the better known "RK-05"
I had a memory fault -- the RLs were the RL-01 and RL-02.
> >
> > 14" media, in a 'cartridge'. I -think- it was an 'SMD' interface
>
> 14" could be true as it just fitted into a 19" rack.
Virtually all 'removable platter' or 'removable pack' storage of the day
was 14" media. :)
There were some "high-capacity" _non-removable-media_ drives that used
much larger media. A friend had a coffee table made from a 45" disk
platter.
> SMD? I have no idea. It was something others did not use I have known then.
SMD ("<S>torage <M>odule <D>evice") was a relatively standard interface for
'minicomputer' type disks. It dates from 1973, and is derived from DEC's
"RP-0X" interface, used on their bigger systems. Some machines used a
'manfacturer proprietary' interface, A little digging seems to indicate
that the smaller DEC drives =were= mamufacturer proprietary'
> SCSI came only later, ST506? Did it exist already?
The PDP-11 was there first. <grin>
Seagate Technologies developed the ST506 drive (5mb, 5-1/4" 'full height' form-
factor) in 1980. The interface definition was extended to support the ST412
(10mb, same form-factor)) drive option used in the original IBM PC/XT. All
the 'smarts' for data handling lived on the controller card, so, by changing
the controller card, you could change the dats storage caapacity of the drive.
drives were generally rated their capacity using a MFM controller -- the
data encoding used by the first seagate controllers. Later a form of
elementary data compression -- 'run-length-limited' coding -- allowed one
to incrreas the data stored on any given drive by about 50% relative to the
MFM encoding. There was a third encoding method -- proprietary to a company
named Priam -- that roughly doubled the MFM storage capacity on a given
drive.
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