1 May
2009
1 May
'09
6:45 p.m.
All,
Thanks to the kindness of Richard Lynch, I now have the 8" drive cabinet
to go with my newly-repaired Xerox 820-II. The drive mechanisms were
non-functional, unfortunately, so I need to scrounge together something
from my junk, err parts collection.
I cannot find anything definitive regarding compatibility. I thought
these machines could use DSDD drives (one site mentioned Shugart SA851s),
but that would be 1.2M of capacity and everything I've found on the web
indicates perhaps 1/2 of that.
Can anyone tell me what will work with the unit and what low-level format
it writes?
Steve
--
2 May
2 May
7:22 a.m.
On 5/1/09 5:45 PM, "Steven Hirsch" <snhirsch at gmail.com> wrote:
All,
Thanks to the kindness of Richard Lynch, I now have the 8" drive cabinet
to go with my newly-repaired Xerox 820-II. The drive mechanisms were
non-functional, unfortunately, so I need to scrounge together something
from my junk, err parts collection.
I cannot find anything definitive regarding compatibility. I thought
these machines could use DSDD drives (one site mentioned Shugart SA851s),
but that would be 1.2M of capacity and everything I've found on the web
indicates perhaps 1/2 of that.
Can anyone tell me what will work with the unit and what low-level format
it writes?
Steve
Both of the non-functional drives that were removed from the cabinet were
851s, and a large percentage of the 820-II floppies that I'm in the process
of archiving are DSDD.
Richard
4:37 p.m.
On Sat, 2 May 2009, Richard Lynch wrote:
> Thanks to the kindness of Richard Lynch, I now
have the 8" drive cabinet
> to go with my newly-repaired Xerox 820-II. The drive mechanisms were
> non-functional, unfortunately, so I need to scrounge together something
> from my junk, err parts collection.
>
> I cannot find anything definitive regarding compatibility. I thought
> these machines could use DSDD drives (one site mentioned Shugart SA851s),
> but that would be 1.2M of capacity and everything I've found on the web
> indicates perhaps 1/2 of that.
>
> Can anyone tell me what will work with the unit and what low-level format
> it writes?
Both of the non-functional drives that were removed
from the cabinet were
851s, and a large percentage of the 820-II floppies that I'm in the process
of archiving are DSDD.
Interesting. So the maximum capacity was approx. 1.2MB on those
diskettes?
I found an SA851 in my collection that I believe works and am working on
getting another.
One thing I should have asked: Can you tell me the jumper settings on the
units you pulled?
Steve
--
3 May
3 May
10:55 a.m.
The 820-II 8" samples in my library show 77*1*26*256 and 77*2*26*256
formats. My 820-II drives were originally SA-800 single-sided
models, replaced with double-sided units.
I believe that alternative ROMS were also offered by third parties.
I believe that there might be source code for the BIOS ROM for the
820-II wandering around also. There certainly is for the Ferguson
Big Board, which is a close relative.
--Chuck
2:42 p.m.
On Sun, 3 May 2009, Chuck Guzis wrote:
The 820-II 8" samples in my library show
77*1*26*256 and 77*2*26*256
formats.
That's fairly conservative, but works out to almost a 1MB for the DSDD
diskettes. Most systems I'm familiar with formatted at 32 x 256 in DD
mode.
I believe that alternative ROMS were also offered by
third parties.
I've found a couple of examples out there.
I believe that there might be source code for the BIOS
ROM for the
820-II wandering around also. There certainly is for the Ferguson
Big Board, which is a close relative.
Would be interested in the "official" sources if anyone can point me to
them.
Steve
--
4 May
4 May
11:14 a.m.
Steven Hirsch wrote:
On Sun, 3 May 2009, Chuck Guzis wrote:
What?! Using what controller chip? How that's even possible while
maintaining the same 360rpm?
jS
The 820-II 8" samples in my library show
77*1*26*256 and 77*2*26*256
formats.
That's fairly conservative, but works out to almost a 1MB for the
DSDD
diskettes. Most systems I'm familiar with formatted at 32 x 256 in DD
mode.
11:48 a.m.
On 4 May 2009 at 10:14, js at cimmeri.com wrote:
Steven Hirsch wrote:
The only time I've ever seen 32x256 on an 8" track it's been with
hard-sectored media. I do have a 30x256 8" format in my library
(Lobo) but nothing more than that. OTOH, 16x512 is quite possible
and used by several systems, including Tandy and Zenith.
--Chuck
On Sun, 3 May 2009, Chuck Guzis wrote:
What?! Using what controller chip? How that's even possible
while
maintaining the same 360rpm? The 820-II 8" samples in my library show
77*1*26*256 and
77*2*26*256 formats.
That's fairly conservative, but works out to almost a 1MB
for the
DSDD diskettes. Most systems I'm familiar with formatted at 32 x
256 in DD mode.
5:11 p.m.
On Mon, 4 May 2009, js at cimmeri.com wrote:
Steven Hirsch wrote:
> On Sun, 3 May 2009, Chuck Guzis wrote:
>> The 820-II 8" samples in my library show 77*1*26*256 and 77*2*26*256
>> formats.
> That's fairly conservative, but works out to
almost a 1MB for the DSDD
> diskettes. Most systems I'm familiar with formatted at 32 x 256 in DD
> mode.
What?! Using what controller chip? How that's
even possible while
maintaining the same 360rpm?
Too early in the day... Just checked the sources for the formatter, and
it's 30 256-byte sectors per track not 32.
--
5 May
5 May
12:08 p.m.
Steven Hirsch wrote:
Too early in the day... Just checked the sources for the formatter,
and it's 30 256-byte sectors per track not 32.
So clarify this for me. Someone figured that they could squeeze more
out of a track than the IBM System 34 standard? How was this done? By
decreasing decreasing the gap lengths?
jS
That's fairly conservative, but works out to
almost a 1MB for the
DSDD diskettes. Most systems I'm familiar with formatted at 32 x
256 in DD mode.
What?! Using what controller chip? How that's even possible
while
maintaining the same 360rpm?
12:42 p.m.
On 5 May 2009 at 11:08, js at cimmeri.com wrote:
So clarify this for me. Someone figured that they
could squeeze more
out of a track than the IBM System 34 standard? How was this done?
By decreasing decreasing the gap lengths?
Exactly. After all, IBM did it--the original 160K 5.25" disks for
the 5150 were 8*512 and by DOS 2.0 had been expanded to the 9*512
180K format. It's possible to reliably fit 10*512 on a 2D 5.25"
diskette on a PC with reasonably "modern" drives, but the gaps get
very small. Many CP/M formats left off the IDAM to make room for
larger gaps when the 10*512 format was used, but that's not an option
for a stock 765-based controller.
On an 8" drive, the limit is 30 sectors for the 256 byte soft-sector
floppies.
Cheers,
Chuck
5538
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9 comments
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participants (4)
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cclist＠sydex.com -
js＠cimmeri.com -
richardlynch3＠tx.rr.com -
snhirsch＠gmail.com