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Well, Thanks Jim for the update. In my absence maybe you never found my obituary so decided to reply. Sure glad I don't work for you, expect my raise may be sub 0%. I'm digging back toward my IMSAI workbench and hope once holidays pass (another excuse) I will have nothing better to do. Glad you...

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...

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...

Sorry to defer, but I am a bit involved in my current S-100 project. I have my 5.25 drives hooked up now on the S-100. I taking vacation (if you permit) for a few days. I will try to respond back late next week. Sorry for delay.

Hi JG, I guess I should read more than I write, but this one item caught my eye. You talked about read data coming out of an SA801 drive when there was no disk in the drive. Just to confirm you are not crazy (or ... both of us are) I saw the same issue with data coming out with my drive door...

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...

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...

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...

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...

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...

We had rain and wind most of the time at the cabin; my curse this year. Didn't catch a fish for the first time ;-{ My 75188 didn't arrive; almost like coal at Christmas, maybe tomorrow. I tried formatting an 8" drive before I left and was getting drive not ready (error code A1 I recall); I think...

I am going to replace U40. Below I show that U40, essentially an inverter that converts TTL to RS232 compatible signals, progressively gets narrower high output pulses. I ordered one off the bay today. The part in the PCA is an Onver QC 1488, but the schematic says it should be a 75188. I...

Above U41 should have been U40, 75188, Tx output 8 seems to stop matching inputs 9 and 10 exactly. Pulses on the output shrink. This takes a while to happen. I'm checking the +/- input voltages as soon as it flakes out tonight.

Well - Silly I have not posted this before. Here is the system with a RAM-32 card installed. As I said before I also have 2x RAM-16 cards plus some other cards. Has a DIO/PDS disk controller as noted way above. The MPU-B rev 1.2 has some wires on the back on U18, but maybe one or more others. I...

Still having serial port issues. I found a different 6 MHz crystal at my local surplus store. I know crystals can have different characteristics, but what the heck, I tried it yesterday. The serial port seemed to go flaky in less then a few hours. Frequency in and out of the 8085 looked OK...

This is my weak code to write a 5.25 disk with a DIO/PDS card setup . I tried to make notes where changes would be made to support 8" drive; maybe only I can understand them. I tried to make a constants area to hold some of of the variables to make the code more portable; I need to do a bit of...

So the serial port has "appeared" to be giving me trouble; time to take a step backwards. I changed the switches on the MPU-B back to the parallel port and re-installed the VIO card and analog monitor. I left this up overnight and it continued to work fine the following morning being able to...

Missed a couple ;) https://secondhandsongs.com/performance/642

Only report today was when I woke up the serial port was in the ditch. Junk from the port and then it hung up. I powered off for about 8 hours and it seems back and happy. I'll have to play now and see what revelations I come with. I thinks this covers PS2 - I responded a day later. For PS and...

I am still plugging. I got to the point that I think my drives may be OK. I next spent too much time getting the serial port option for "monitor" output working, but it is. (Again "monitor" is the lowest level of communicating with the MPU-B, like the MPU-B BIOS) I wanted to use a terminal...