>
>Subject: Re: Imagedisk 1.17
> From: "Dave Dunfield" <dave06a at dunfield.com>
> Date: Fri, 27 Jul 2007 07:11:40 -0500
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>> Lately I've found a very nasty bugs in IMD 1.16 (at least with a secondary
>> FDC, tested on two different machines of different speed with different
>> FDC). Reading disks is mostly fine, but writing to a drive connected to a
>> secondary FDC doesn't work reliably. The problem is that the drive won't
>> step properly, i.e. sometimes it misses a step pulse which makes the
>> written disk unusable. The same problem occurs e.g. with the clean head
>> routine. I had a look on your source code and I think it's a timing
>> issue. I've inserted a small delay ('delay(55);') into the seek routine
>> (between line 998 and line 999 in version 1.16) and this solved all the
>> problem. I think that the seek routine is called too early after having
>> sent the previous command to the FDC although it shouldn't matter because
>> wrfdc officially waits for the FDC to be ready before sending a byte. But
>> apparently some (many? all?) FDCs appear to be in a ready state although
>> they are not yet ready to do a seek... really weird.
>
>It's impossible to test every FDC (at least in a free project). This
>explaination doesn't make sense because the seek routine has a 55ms settleing
>delay at the end (which you can increase with the SD= option), and the clean-
>head routine has a 100ms delay between seeks, which makes a total of 150ms
>delay. There are no other intervening commands during "clean heads" - since
>seek() waits for seek complete, 150ms should be plenty of time for the
>controller to be ready for another command. This also does not explain why
>reading a disk would work, so I suspect there is some other factor involved
>here..
>
>This is the first I've heard of this problem - if you have problems with
>ImageDisk, the best way to get it fixed correctly might be to work with
>me on it instead of posting "fixes" to public forums. But... thats what
>happens when you release source code.
Ah, the step gremlin. It's an old 765(all!!!) problem. The problem is when
the step pulse is set to minimum acceptable for the drive it's possible that
due to internal timing of the 765 it can shorten the step timing of the
first pulse by 1 count. If that occurs many drives seek badly and you get
read or write errors because your not where you thought you were.
Note: some old drives due to the lubricants turning to goo will also exhibit
this type of error. There is one solution, step slower (SRT+1).
Another problem is the 765 was designed for 77track drives (8" floppy)
and there were no 80track minifloppies. So the Recal only issued
77 step pulses and would flag an see error if the drive was 80track.
One fix is to issue a new Recal and see if the drive properly homed
this time. The problem is there are some cores that fixed this and will
issue up to 256 step pulses. The problem can also arise when using
SA400/400L style drives ans some (not all) will jump track (loose
the groove on the positioner disk) if stepped too far past tracks
000 or 39.
Last gremlin is the 765(and cores) were designed to Seek/Recal up to 4
drives but PC hardware does not always decode this and may have drive 0
also appearing as drive 2 or 3 which makes it susceptable to being
repositioned by commands not intended for it.
Allison
I just collected a Victor machine which I believe to be the 9000 aka
Sirius 1, although it does not have a model # anywhere I can find.
The fans and drive powers up, but the display does not. It appears to
get its power via the 9-pin signal cable. Can anyone confirm that
this is the case and if this is a common issue, perhaps with an
equally common fix?
-j
--
Retrocomputing and collecting in the Chicago area:
http://chiclassiccomp.org
>
>Subject: Re: Reading NorthStar Horizon hard sector disks on PC
> From: "Chuck Guzis" <cclist at sydex.com>
> Date: Tue, 31 Jul 2007 09:18:41 -0700
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On 31 Jul 2007 at 9:53, Dave Dunfield wrote:
>
>> Also, the N* disks are hard-sectored. This means that the controller
>> needs to see the individual holes to know where each sector data
>> starts. The PC disk controller has no means to aligning individual
>> sector data to index holes, even if it could see the sector data.
>
>Not all Northstar diskettes are HS. One of the models (Advantage?)
>isn't--and it's that format that the Microsolutions MatchPoint will
>read, not the others. It's been too long since I've seen the darned
>things...
Error! Advanatge is the same format as the MDS [Aka Horizon) and does
both SD and DD formats. Least mine does.
I believe there was an aftermarket board that would fit the Advantage
bus (non S100) to provide things like a soft sector FDC. There was
also a hard disk controller.
Allison
>
>Cheers,
>Chuck
I'm getting a little closer ..
I have the power adapter now and the correct cabling. This device
communicates over the serial port, but I have no idea how to talk to it,
and I haven't even been able to get it to transmit noise on the serial
port to the host PC. (I've tried a variety of bps rates.)
Does anybody have IBM book SA23-2646-01 "Hardware Technical Reference:
Options and Devices" ? The protocol for speaking to this thing might be
in there ...
If anybody else has one connected to a PC RT or an old AIX box, it would
be possible to reverse engineer the protocol by tapping the serial cable
and watching what comes across.
It's a neat looking piece of hardware - 32 buttons, each having a
controllable indicator light. But I'm getting grumpy because I have no
idea how to feed it. :-(
Thanks in advance,
Mike
I've got an IBM PS/2 Model 25 that I want to put into use as an
infrequently-used terminal using its serial port. I have a few
questions and was wondering if someone could give me a hand:
- Is there IBM PS/2 Model 25 tech and/or repair specs online somewhere?
I figured out how to open the back up, but that just gets at the ISA
slots. I need to get at the floppy drive; I want to know what some of
the 40-pin male connectors are; etc. Which leads me to my next question:
- The floppy drive is toast. Can I replace it with any regular 3.5" HD
drive, or is it unconventional in some way?
- The embedded monitor is ailing (it's dim, and white has a bluish tint
leading me to believe that the red and green guns are giving out). Is
there any way to fix that without jumping through hoops, or is it (no
pun intended) terminal?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
On 7/31/07, Bill Sudbrink <wh.sudbrink at verizon.net> wrote:
> My wife does doll houses now and then. I have wondered whether a
> fully functional (front panel, that is) 1/12 scale IMSAI would be possible.
> Z80 processor, 64K RAM, maybe a few interesting front panel programs
> in ROM... flip the bit, cylon eyes, simple count up/down. Run on a
> watch battery.
Hmm... A real IMSAI is what, 10.5" tall, 19" wide, and about 24"-36"
deep? That sounds difficult to reproduce at 1/12th scale, but it
might be possible to replicate an IMSAI front panel with fiber optics,
run them under the floor of the doll house to a hidden Z-80 board
(that could still be done with a lot of SMT to make it small).
It comes to mind that a microSD card is on the close order of the
dimensions of a 1/12-scale 8" floppy ;-) (2/3" x 2/3")
-ethan
A reference was made to MicroNova. Like Data General MicroNova? Like the MicroNova that?s in my lock up, that I haven?t
run in 15 years? Like the MicroNova with the 16 or 32 serial ports, I don?t remember, for terminals? Like the MicroNova I lost
the 10M washing machine platter drive from? Then threw the removable platter out because I couldn?t find the washing machine?
That MicroNova?????????
Kevin J Andres
Senior Technician
Engineered Protection Systems Inc.
HYPERLINK "mailto:kandres at epssecurity.com"mailto:kandres at epssecurity.com
No virus found in this outgoing message.
Checked by AVG.
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I believe you're thinking of the book "The Art of Digital Electronics"...I
don't remember who wrote it. I too have been considering building an 8/i
compatible, and wouldn't mind some insight.
Devon
Ethan Dicks <ethan.dicks at gmail.com> wrote..............
Subject: Re: newbie building a scratch-built computer
-----------------------------------------------------------------------------------
There is _lots_ of software for that platform, of course. The PDP-8
has a rich history.
I've been re-reading a book on processor design I picked up a few
years ago, based on a recommendation on this list. I am blanking on
the title, but it describes a 74183/74181-based F20 and a 2910-based
microprogrammed F30 PDP-8/i-compatible CPU. I've been mulling over
what it would take to build one of those (besides lots of time ;-)
On 7/31/07, Chuck Guzis <cclist at sydex.com> wrote:
> On 31 Jul 2007 at 1:11, woodelf wrote:
>
> > All of it (8K+) with serial I/O to boot is my guess.
>
> That was my thought. Why fool with IM6120s when you fit the durned
> thing in a teacup? How about a handheld 8/i? Maybe a few MB of CF
> for storage and an LCD display for a terminal...
Hmm... that does sound interesting. A 320x200 LCD panel isn't
expensive (I have several raw ones on hand w/touch sensors), and could
be driven to 80 cols w/a 3x5 font (as was once used to give the C-64
"80 columns"). A "really cheap" terminal could be an older Palm Pilot
running one of the extant terminal emulators, sharing a new enclosure
with the PDP-8 board, attached internally via TTL serial.
> Might make an interesting coversation piece.
I think a 12-bit hand-held would be pretty cool.
-ethan
