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IMSAI PCS-80/35 or maybe an IMSAI 4x

Tried a write tonight, but got an error 94, CRC error in the ID field.
This will take a bit of investigation.
I don't have true SSSD disks so I was trying to format SSDD as SSSD.
Maybe you can get a laugh about this and pass on a hint.
The format seemed to go OK
I had tried to read track 2 sector 3 from my formatted disk and I was getting NOT READY from monitor.
I was convinced monitor was not detecting my 8" drive and sending the command to the 5.25" disk command address.
The IMSAI DIO has two different entry points for commands one for 5.25 and one for 8" drives.
I could see the correct disk command in disk buffer 0, 0x0080.
Now I am thinking that there is some issue with the format....
Time to get the scope out.
I got my 75188 serial translator today, but the system seemed to be working OK, so I didn't take the time to swap it out.
I'll leave it up tonight and make sure the serial output goes in the tank.
I am actually getting younger as I work on this.
In my last post I said I would reply the next day, which I did, but the time says 2 days have passed.
I hope you see the benefits of posting on this forum.
My white paper will be out in August on means to to slow aging.
Al
 
My serial port began acting weird again so the MPU-B came out.
I swapped out U40 with a new TI 75188 thanks to the eeebay.
Still running to see if I fixed it or I have to go to the mountain of contemplation.
I went with my son today and managed to get some 8" SSSD disks from my donor organization.
These were used, but am giving them a try.
We used a bulk eraser to hopefully clean up the disks.
I have two 8" drives, but I think I am seeing read data coming from one of them when the head is not loaded.
SA800 TP 16 was what I was looking at.
This is the drive I have been using up until now.
I moved over to the other drive and have formatted two of the SSSD disks I got.
I start my write routine to write 0x1000 bytes, or 0x20 sectors.
The write stopped at sector 0x0B (maybe actually 0x0A; need to look at my code) with an error code of 0x94, CRC error in the ID sector.
The ID sector is "overhead" (not useful data to the user) of any disk record and contains the track, sector and head info and is CRC protected; lets the drive know if it is in "Kansas" (right place) or not.
I will try another disk tomorrow.
Serial port is still hanging in there.
...
I think you should listen to this (tonight as it is):
Al
 
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Well the serial port "seems" to be hanging in there.
I will not power down the IMSAI chassis and keep dumping memory (such as d 3000,3FFF for monitor commands) for a few days until I can say the serial port is solid.
Fingers crossed I don't have to deal with this again.
As a side note I have been changing Teraterm serial port settings to 50ms for transmit delay.
I was at 200ms, and 50ms seems to be working and I feel about 4x better ;).
It was taking quite a bit of time to load the partial data image I was trying to write (0x1000 bytes / 0x20 sectors of data).
The speed up has helped.
At some time I want to find out just how fast I can throw characters at the MPU-B before it starts dropping characters.
I don't think this is the time (until I reach some sort of stability).
So as a bad scientist I repeated my write to my disk described above and again tonight and it stopped at sector 0x0A or 0x0B (I think 0x0A) with the 0x94 error again.
I hope i don't have to to describe bad science, I think I just described it.
Well, I've got a big batch (10) used SSSD disks (thanks G33ksquadmn), so I thought tonight would be dedicated to formatting these (actually 9 disks, the one with the issue was formatted).
Format / write time is for an 8" SSSD Shugart drive ~ 12.6 seconds per sector, so to format the disk it is just over 16 minutes.
I'll format all of these and see if I keep stopping at the same sector in my code
This will hopefully delineate if I have a bad drive or a bunch of disks that will not write past track 0 sector A.
BTW - My code seems to have worked for the 5.25 disks, never stopping until the write area had been written to the disk.
I have been editing my code and adding more comments to allow formatting and writing with the IMASI DIO-C and just running from the monitor.
I will review and send an update in the next day or so.
In my code I only have 0x1000 / 0x20 sectors of space at 0x2000 to 0x2FFF; I need to make an updated version to relocate the code to 0x2000
and the write data area to 0x3000 to 0x7FFF, or 0x4000 to 0x7FFF to make it a bit more usable.
Something for my free time.
I really like the Beach Boys song I left last night; my wife said it was too melancholy.
Thoughts?
I'll pick it up a bit with the next song - CB - Guess who is this.
Al
 
Well I formatted my 9 other disks; I don't know if IMSAI monitor does any other validation.
I'm beginning to think not, just write.
With my 10 disks I have tried about 4 or so with varied results.
With some I wrote a few tracks, some none.
With some I have had slightly better success on inner tacks.
Sorry, but I have fallen into a bit of bad science; poor data collection.
I was just whipping through 4 or 5 disks and seeing what they would do.
I got into a bit of a rhythm trying to write tracks 0, 0x20, 0x40, and then like 0x48.
Almost similar results.
I swear I was getting 6, 8 maybe a few more to write before I was getting the 0x94, index not found issue.
Now I am only getting 1 or 2 before the 0x94 shows up.
This is getting me to think:
A. Look at the write data on a format and see if it looks OK
B. Go back to drive 1 and see what I am getting out of it; I thought I was getting read data pulses on the SA800 with the carriage open.
C. Suspect something on the DIO where the SA400 / SA800 data converges.
I think this the right order.
A small ray of optimism; serial port has been rock solid for a few days continually powered up.
The U40 replacement seems to have been the trick.
I found a nifty iphone app that lets me check the drive speed - I'll insert below.
It doesn't tell you the speed, but you adjust it until your moving object stops moving.
My drive 2 speed is within spec.
Well, my hint was CB for a song.
Maybe you have guessed the artist.
I have asked my dear son and and numerous colleagues opinion; none responded.
I clearly have bad taste in music.
Deal with it ;)
Speed shot:
SA800-2-Speed.JPG
Courtney:
 
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So I went through all of my 8" SSSD disks on my drive.
All were either stalling on track 1 or 2 (this is 1 based indexing for track number).
All reported 0x94 error, error in the index field CRC.
This 8" drive may take some work.
Not sure if it is my DIO card or the drive.
I never really discussed the DIO card I have; maybe I am still not sure.
DIO cards seemed to have existed in (at least) a DIO-A (maybe just DIO) DIO-B, DIO-C, and DIO-D.
From the "MDIO-disk_sys_ref_manual.pdf" page 34:
DIO-A (1st DIO version I believe) supported, 2 formats, Format 1, an IBM 3470 SD format (not sure if it supported SSSD and DSSD) and a format V a 128 byte DD format for standard drives only.
DIO-B seemed to be a 1 off that supported CalComp 142 (I have no idea what I am writing here) with a different (sector) step rate.
DIO-C SD and DD on 8" drives
DIO-D SD and DD on 5.25" drives.
I think there is one more, maybe a super variant, out there.
I'm pretty sure I have a DIO-A.
The strange thing is I thought I saw an image of a DIO-D with both the 32 and 50 pin drive connectors installed, but the 50 pin had a blank connector installed.....
...
Because I believe I have the DIO (DIO-A) I should be able to support both 5.25 and 8" SSSD drives.
Why the heck can't I format, write and read my 8"-ers.
...
Regression testing....
I yanked the 8" drive tonight and went back to the 5.25 drive.
I read the disk I had formatted and written in the drive 1 (1 indexed) location and repeated the read with drive 2.
Both drive read what I wrote just fine.
The DIO (and PDS - P?? Data Separator; separates the FM clock from the FM data) seems to be working fine for the 5.25 drives.
I am going to look at the data stream on the 5.25 tomorrow or the next and get timing.
I'll post the bit frame timing of the 0s and 1s and maybe an example of 0s and 1s being read from the disk on the 5.25.
Then back to the 8" for comparison.
...
After numerous appeals to US domestic folks on last night's song, without response, I am certain I am getting ghosted.
I'm getting use to it.
Love Al
 
Here is a data stream from the 5.25 disk measuring on the SA400 TP6.
It is listed as +data , it really looks like -data.
I inverted my channel for the capture.
The disk is formatted (FM encoding) and the format data is 0xE5
The first clock of the FM data starts at the not edge of the scope trace, but the next (second vertical graticule)
Starting there you will see the first rising clock edge followed by the next rising edge that is the "1" data.
Follow this pattern further and you will see two more instances of this followed by a clock edge, but no data in the expected time.
This is the first "0" zero of the 0xE5 data - clock "1" clock "1" clock "1" clock "0", 0xE.
The balance of the trace shows and additional 0 1 0 1 with the clock pulses in between if you get the pattern.
This byte happens to the the first bit of the sector.
What precedes it is is the AM byte that tells the system if the sector is "live data" or "deleted data" - 0xFB or 0xF8 respectively.
This trace only shows the first 0xE5 of the data in the sector.
I think there is something different in the architecture of the clocking of the AM field; I think missing clock pulses for maybe bytes 3-5;
it escapes me now.
I need to go back and read more; I could be messing up FM and MFM recording.
Who in the world is looking at this bologna anyway?
I am going on a little time off, just a few days.
I was thinking of taking the IMSAI, but I realized I wouldn't have AC power ;)
Maybe time for reflection.
Enjoy your week.
Maybe enjoy this song below the screen of the 0"s and 1"s; a little music lession
Al
5.25-Format-Data-Read-E5.JPG
 
Well my hiatus does not seem to be noticed; I'll get back to my IMSAI toils as time permits.
Had a nice trip to the Porkys in MI.
Good hikes, nice times with friends.
Throw in a funeral, work and bad bearings on the pontoon trailer, a fishing trip to Leach lake, and poof, time fly's.
Now the only obstacle is the MN State Fair, and a cabin trip or two.
Promise to get back to this stuff as soon as my free time expands as a function of other life interference's and pleasures.
Why work on computers when you can hike here in MI:
Porkys.JPG
 
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