14 Nov
2007
14 Nov
'07
1:28 a.m.
Subject: Re: Tarbell is making me insane
From: Grant Stockly <grant at stockly.com>
Date: Tue, 13 Nov 2007 11:34:53 -0900
To: "General Discussion: On-Topic Posts Only" <cctech at
classiccmp.org>
More to add...
I know that writing to 3.5" HD disks with the hole covered to make
them look like DD is frowned upon, but maybe it could help determine
why I get errors with the real DD disks.
While trying to back up my DD disks onto HD hole covered disks I got
an error. Its not the disk because I've tried two and they both fail
at the same spot.
Bad write or media, or dirty head scaring disk.
Also, are DD disks the same as Single Sided 3.5"
360/400k
disks? Except for the double sided part?
I use a stack (about 200) of written once disks, they have sales
promo and utility on them and never distributed. Good media
and easily erased.
What are good sources for DD disks TODAY, not NOS
disks, but new
disks? Is athana the only place out there making DD disks?
When copying from drive A to drive B it has an error at the end of
the disk. Is this where a data rate issue would be the worst?
Inner tracks are always worst.
A>stat *.* | B>stat *.*
|
RECS BYTS EX D:FILENAME.TYP | RECS BYTS EX D:FILENAME.TYP
0 0K 1 A:.INT | 64 8K 1 B:ASM.COM
64 8K 1 A:ASM.COM | 96 12K 1 B:BASIC.COM
96 12K 1 A:BASIC.COM | 8 1K 1 B:COPY.COM
8 1K 1 A:COPY.COM | 70 9K 1 B:CPM.COM
70 9K 1 A:CPM.COM | 38 5K 1 B:DDT.COM
38 5K 1 A:DDT.COM | 12 2K 1 B:DISKTEST.COM
12 2K 1 A:DISKTEST.COM | 24 3K 1 B:DUMPDSK.COM
24 3K 1 A:DUMPDSK.COM | 48 6K 1 B:ED.COM
48 6K 1 A:ED.COM | 4 1K 1 B:FORMAT.COM
4 1K 1 A:FORMAT.COM | 56 7K 1 B:PIP.COM
56 7K 1 A:PIP.COM | 0 0K 1 B:RUN.$$$
92 12K 1 A:RUN.COM | 24 3K 1 B:STAT.COM
24 3K 1 A:STAT.COM | 8 1K 1 B:SYSGEN.COM
8 1K 1 A:SYSGEN.COM | BYTES REMAINING ON B: 11K
BYTES REMAINING ON A: 0K |
| B>
A> |
And the error:
A>PIP B:=*.*
COPYING -
CPM.COM
SYSGEN.COM
DDT.COM
COPY.COM
PIP.COM
ASM.COM
STAT.COM
ED.COM
FORMAT.COM
DISKTEST.COM
DUMPDSK.COM
BASIC.COM
RUN.COM
DISK WRITE ERROR: =*.*
A: R/O, SPACE: 0K
B: R/W, SPACE: 11K
A>
(can't be too save with my only good boot disk, A:. :)
Disk write error... likely just not making it.
FYI: 3.5" disks were never meant to run at 125khz. The
720k mode is 250khz and the 1.44mh is 500khz. The read
amps just may not work well down that low.
Allison
Grant
14 Nov
14 Nov
7:57 a.m.
FYI: 3.5" disks were never meant to run at 125khz.
The
720k mode is 250khz and the 1.44mh is 500khz. The read
amps just may not work well down that low.
Do you think that it would be better if I were to get the Tarbell to
run at 4MHz (250kHz)?
I'd have to make a new BIOS and modify the format program. I don't
have source for the format program. Does anyone off hand know where
source to the Tarbell CP/M utilites could be found?
I should be able to format the disk as 36 sectors 80 tracks and
possibly configure it to use both sides. That would be formatting it
to capacity...
I'm going to write a disk image tool that dumps the disk to my
computer. I could write one that also writes an image to a disk.
What do you think would happen if I were to try to use the disk at
250kHz but only put half of the sectors? Will the 1771 handle the
extra time or give me errors?
This faster signal might be better for the disk drive?
It may seem strange I'm fighting with this so hard, especially since
I'm working on Altair disk drive system emulator using SD cards, but
nothing beats real live hardware. : )
Grant
8:27 a.m.
On 13 Nov 2007 at 22:57, Grant Stockly wrote:
Wait one darned second. There's a lot of confusion here--many
vendors refer to the *data rate*, not the actual clock. Since the
1771 is an FM-only chip, that translates to 2 cells per bit time, or
a 250 KHz clock rate. The frequency of the clock at pin 24 of the
1771 should be 1MHz. If it's 2MHz, it's running at the 8" rate
(500KHz = data rate of 250KHz).
I don't know which Tarbell card you've got, but if mine is anything
like yours, Don takes a crystal at 2x the required clock and divides
it down by 2 with a flip-flop (the 1771 requires a 50% duty cycle
clock and is not very forgiving).
On my controller, Don uses a couple of LS161s and some gates to form
a data separator. I'm not thrilled with it--the bit shift on the
inner tracks of your 3.5" drive are probably on the edge of causing
it to lose sync. You might want to run some pattern-generating
diagnostic tests to see if anything really pushes it over the edge.
You can get around this by limiting your use of the inner cylinders
(just tell CP/M that you've got, oh, 70 tracks instead of 80) or you
can junk the onboard separator and replace it with a somewhat more
modern WD9216 8-pin DIP.
Let me know if any this doesn't make sense.
Cheers,
Chuck
FYI: 3.5"
disks were never meant to run at 125khz. The
720k mode is 250khz and the 1.44mh is 500khz. The read
amps just may not work well down that low.
Do you think that it would be better if I were to get the Tarbell to
run at 4MHz (250kHz)?
8:52 a.m.
At 11:27 PM 11/13/2007, you wrote:
On 13 Nov 2007 at 22:57, Grant Stockly wrote:
Wait one darned second. There's a lot of confusion here--many
vendors refer to the *data rate*, not the actual clock. Since the
1771 is an FM-only chip, that translates to 2 cells per bit time, or
a 250 KHz clock rate. The frequency of the clock at pin 24 of the
1771 should be 1MHz. If it's 2MHz, it's running at the 8" rate
(500KHz = data rate of 250KHz).
I'm sorry about that! : ) Right now it has a 2MHz crystal to run
the 1771 at 1MHz. I forgot all about the divider...
Grant
FYI:
3.5" disks were never meant to run at 125khz. The
720k mode is 250khz and the 1.44mh is 500khz. The read
amps just may not work well down that low.
Do you think that it would be better if I were to get the Tarbell to
run at 4MHz (250kHz)? 
8:37 a.m.
New subject: Tarbell is making
I don't recall ever running a Tarbell single or double density
controller in a system with a 4mhz cpu.
Exception to that was running it in a Tarbell CPU equipped system
I always had an Imsai backplane for what that is worth.
I also had a Northstar system which I merged the BIOS with the Tarbell
controller, so I could dub 8" to 5 1/4" HS floppies, and never had much
problem with that.
All of my Tarbell hardware was tuned up by Dick Culberson or Don for
what that is worth.
Both have passed away, and are not around to help with this discussion.
Jim
8:26 a.m.
On Tue, 2007-11-13 at 20:28 -0500, Allison wrote:
I use a stack (about 200) of written once disks, they
have sales
promo and utility on them and never distributed. Good media
and easily erased.
I bought a box of 500 DSDD floppies from a guy on eBay. They appear to
be new. They seem to be pretty good quality too - the cases are a bit
naff and plasticky but they actually work.
I still don't understand how brand new 1.44M floppies fail after two or
three uses, but the 20-year-old SSDD disks for my Ensoniq Mirage are
still perfectly readable.
Gordon
6262
days inactive
6262
days old
5 comments
5 participants
participants (5)
-
ajp166＠bellatlantic.net -
cclist＠sydex.com -
gordonjcp＠gjcp.net -
grant＠stockly.com -
jwstephens＠msm.umr.edu