16 Dec
2009
16 Dec
'09
11:05 a.m.
I wonder why
HP went away from the 9914 in the drive units (all later=20
drives seem to use either the 8291 or the Medusa) while keeping it in=20
the host computers.=20
=20
I've wondered about that too. I wanted to use a G/HPIB ISA card with a
cheap PC to emulate the then more pricey 9134 and I was told that it was not possible to make a 9914 based ISA card talk
Amigo as a device.
But considering that they're used in Xebec controllers that doesn't
I have never actually seen this Xebec controller in an HP drive unit, but
I'll believe it exists.
seem right. What changed in the Amigo/SS/CS-80/IEEE
specs that made it
impossible? I vaguely remember something mentioned about a problem
with how MSDOS talked to discs: by reading/writing sector by sector
instead of files and some associated timing problems. I don't know if
I can;t see why that would be a problem. The HP protocols are all block,
not file, baeed (unlike the Commodore drives for the PET). The drive
doesn't have any idea what OS is talking to the it, it has no
understanding for the directory or the filesystem.
that's correct though, since the Xebec
controllers--both the 1-disc
and the 2-disc talks fine to the HP-150. The only problem with it is
that it cannot format a 10Mb disc; it insists on formatting it as a
single 5Mb. Reads & writes it fine, though.
(I'd like to find out how to format discs on a PC for use in the 9134
drives. I could probably use bigger discs if they could be formatted
properly.)
I wouldn't bet on it. I am pretty sure the later drives, at least (9144H,
etc) check that the hard drive actually matches what is expected (I have
been told the cotnroller tries to select non-exixstant heads and makes
sure the drive asserts the erorr line, things like that).
The 9133V controller (I assume there's a 9134 version, if only becuase
you could trivially remoove the floppy drive and controller from a
9133V) can be jumpered to work in 3 ways :
With a 5M drive (ST406, and no, that isn't a typo [1]), this is a normal
9133V
With a 15Mbyte drive (ST419), that's a 9133XV (I assume you've noticed
that in this case the suffx letters are the capacity in roman numerals)
With a 5M drive (ST406), but configured as 4 logical volumes. It then
appears exaclty like a 9895 8" drive with 3 slaves. IIRC this is the
only hard disk unit that works with an HP85.
I don't think it will access larger drives if you managed to connect and
format one, at least not without firmware mods. Whether it will object to
having a larger drive (ewen if you only want to use 15M of it) I don't know
[1] In other words I don't mean an ST506. An ST406 is a single-platter (2
head) drive, basically half an ST412 (which is a 2 platter, 4 head
thing). The ST419 is the 3 platter ,6 head one. I assume the last 2
digits are the unformatted capacity or something similar.
Incidnetally, the HP ISA HPIB card used to link these drives to an IBM
compatible (and yes such a thing does exist) uses a 9914 chip. I have one
here.
also uses
a 9914.
=20
Every 9121 I;ve seen has an 8291 in it. I have the 'service manual' for= the 3.5" floppy drive units, and while the
only schematics it contains=20
are for PSUs it does contain full parts lists for the controller board =
in=20
the 9121. It states it uses a 8291.
This was from memory. Unfortunately, the 91xx discs are buried deep,
not quickly accessible. I was pretty sure it was a 9914 for some reason. Perhaps I was thinking of the older floppy
drives. Somehow I
I can;t think which ones. The 82901 series (5.25" drives) use the 8291 as
well. I've never owned a 9895 8" drive, so I can't somment on that one.
-tony