[TUHS] Codata progress update

[Engel, Michael]

Hi,

it's time for an update on our progress with the Codata machine.

The serial interface problem was not caused by a defective transceiver
chip (which I found out after buying a couple…), but by an extreme 
amount of noise on the (quite long and old) serial cable we used to
connect the machine to the PC acting as a terminal. Using a USB
to serial adapter and a short 9-to-25-pin adapter cable solved this
problem. Well, try the obvious things first (using a scope helped).
The second CPU board also works, so we could build a complete
second machine with our spare boards if we have another multibus
backplane...

We could get the machine up and booting from the first 8" hard disk 
last Friday. Luckily, an old version of Kermit was installed and we 
were able to transmit a large part of the root file system from single
user more - especially the Unix kernels, driver sources, the build 
directories for the kernel, include files and the build directory for 
the standalone boot floppies. All with a speed of 500 bytes/s (9600
bps serial line minus kermit overhead). cksum was used to confirm
that the files were transferred correctly (this was the only checksumming 
tool that was available on the Codata, I didn't want to mount the fs
read-write and compile software before completing the backup).

I had to shut the machine down on Friday evening (security policy
that kicks you out of the building here), since I didn't want to leave
it running unattended over the weekend. Unfortunately, the disk 
seems to have developed a bad sector in the autoconfiguration 
region (the system seems to be quite modern in this respect). 
The kernel can be booted successfully, but it refuses to mount the 
root fs, complaining about a timeout. There seems to be a complete 
root file system on the second disk (the firmware is able to read files 
from the disk, but it doesn't offer a feature to list directories…), but the 
kernel on the second disk also is hardwired to mount its root fs from the 
first disk. Trying to connect disk 2 as disk 1 resulted in a non-booting 
system...

The good news is that both root file systems seem to be reasonably 
intact so far, I can read text files from the boot monitor. So our next 
step to backup the rest of the system is to build an emergency boot 
floppy. At the moment, however, the Codata refuses to talk to its 
floppy drive. The machine has a Multibus FD controller with its own 
8085 CPU and a uPD765, connected to a Toshiba 5.25" DD floppy 
drive (720 kB, 80 tracks, 9 sectors of 512 bytes), the model identifier
is DDF5-30C-34I (printed on the motor assembly). I couldn't find
any information on that drive online, so I hesitate to simply 
connect a more modern drive due to possible pinout differences.

I also found out a bit more on the SMD disk controller. It seems to
be an OEM variant of the Micro Computer Technology MCT-4300
controller. The only place I could find this mentioned was in a 
catalog of Multibus boards on archive.org. It has its own driver 
(cd.c), there is a separate one for the Interphase 2180 and an 
additional one for the Codata MFM controller.

So, if you happen to have any information on the Codata floppy
controller, the Toshiba floppy or the MCT-4300 SMD disk controller,
I would be happy to hear from you...

-- Michael