19 Nov
2007
19 Nov
'07
11:13 p.m.
On Sun, 18 Nov 2007, Tony Duell wrote:
Interesting. I'd momentaarily forgotten aout the ESDI drive units. I haev
one (I forget the model numbnr), I am darn sure it's an ESDI drive both
Even later, there was the 9153
(floppy/winchester) and 9154 (winchester
only) unit. Again 98B09 based, but now everything in SMD packages (the
68B09 is a PLCC package). The winchesters are HP custom units with a
strange interface -- fairly high level for positioning the heads, but
still the raw bit stream for reading and writing.
Recently the drive in my HP 7958A unit failed (it was a Micropolis 1355)
and I've replaced the drive with another ESDI drive. The 7958A contains a
68B09 (I guess) and a NatSemi DP8466 disk data controller. from looking at it and from reading the boardswapper
guide. But the
controller oard is mostly custom HP chips, along with some RAM, an
EPROM,
and, of course, the 68B09. Even the HPIB chip is HP (the 1TL1 'Medusa' chip).
The drive is also HP. I am pretty use it's not based on a Micropolis
unit, either...
BTW one can use ESDI drives with any capacity as the
firmware will read
the geometry information from the disk drive and setup its internal tables
accordingly. You have to make sure to jumper the drive to hard sectored
mode, 64 sectors/track!
That's well worth knowing. I am pretty sure the ST412-based units, which
of course can't read the drive geometry from the drive hardware, have
tables in ROM of the allowable geometries (link-selected o nthe
controller board) and check it against the drive at power-on (try
selecting non-existant heads, etc). Which means if you put in a larger
drive the darn thing will fualt and a low-level format won't fix it, even
though you only want to use the original capacity of the drive.
-tony