View Full Version : Uploading Disk Images to IMSAI

Ken Vaughn
January 7th, 2011, 02:26 PM
I have been working off and on for some time to get Dave Dunfield's NST (Northstar disk image transfer) program working on a laptop which is communicating with my IMSAI via a serial cable. His procedure of "typing in" the I/O stub (hex file transfer) to the micro using the Northstar Monitor doesn't work for me because I don't have a typical CRT monitor connected to a serial port. On the other hand, I do have a working system with two operational N* disk drives, so I was able to type in, assemble and save the I/O stub configured for my serial port under N* DOS.

I have been using a Win98SE laptop which I booted to DOS to run the PC program which sends and receives files. It won't communicate when running under DOS, but works fine when I run it from the Command line prompt under windows. I ran Checkit (both ways) and it reports the COM1 port is fine. A couple of serial port configuration checkers I tried ran under windows, but not under DOS. I tried the DOS MODE command to set up the COM1 port, but that doesn't make any difference. I wasted a lot of time before trying the PC program under Windows 98SE.

Any idea why the COM port is not working under DOS? No big deal I guess, since I am now able to upload and write N* DOS images, CP/M images, and UCSD Pascal disk images. This leads me to ask another question. Does anyone have a scanned copy of the Fortran-80 user manual (CP/M)? I tried Bitsavers.ORG and H. Harte's website.

January 7th, 2011, 06:03 PM
Have you tried a basic DOS comm package (such as Procomm Plus) and a loopback connector to see if your port will even talk to itself?

Barring oddball interrupt settings or interrupt conflicts, serial port setup should be a no-brainer under DOS.

January 7th, 2011, 08:55 PM
DOS does require the handshake lines (RTS/CTS & DTR/DSR) to be enabled or faked with loopback connections, and of course the baud/stop/parity parameters have to be set with MODE if the software doesn't take care of it.

January 8th, 2011, 02:03 AM
Hi Ken

I'm also in the process of bringing up my IMSAI with CP/M. I had no working boot media. Just the hardware, CCS 2810 CPU, CCS 2422 FDC, RAM16 64K and two Shugart 8" drives. So far, I'm transferring all the images/data to the IMSAI using the FDC cards Monitor ROM. I found the source code for the monitor, added in the Intel HEX recv/xmit command, compiled, burned the EPROM and installed it. I use TeraTerm on a laptop to transfer the images over serial through the monitor and into RAM. The next step that I'm working on is to, bring up CP/M, transfer .COM images in hex to a specified address, then save them to disk through CPM.

I suppose it would be possible to avoid this using 22DISK/Imagedisk with the 8" SSSD floppies connected to the *right* 486 PC. Finding that PC could be more work then it's worth (unless anyone has hints on which models work well).

- Nick

Ken Vaughn
January 8th, 2011, 06:30 AM
Have you tried a basic DOS comm package (such as Procomm Plus) and a loopback connector to see if your port will even talk to itself?

No, I haven't tried running a comm program under DOS, and based on my experience so far I am beginning to question if that would work. The serial port works fine under Win98SE. I have used HyperTerminal (under Windows) to capture data from the IMSAI in basic text capture mode. I also wrote a program on the IMSAI to read the disk one track at a time, convert the data to hex, and send it over the serial port to the laptop. This gave me the ability to capture disk images, although I had to convert them back to binary on the PC. I downloaded 75 or more disks and sent the raw images (NSI format) to Dave Dunfield a couple of years ago. I am also able to mount these disk images and execute programs on a PC using his HORIZON simulator, even though my vintage IMSAI is not a Northstar.

I'm thinking that the problem is something odd about the serial port when booted to DOS on a Win98SE platform. A Google search turned up a couple of threads on other forums which described the same problem. Since it works reliably from the Command line prompt, I'm not inclined to spend more time trying to figure it out.

I broke out a DOS only machine -- a 486DX4 system in a tower case. This box is running MS DOS 6.22 It communicates with the IMSAI just fine, so I am not questioning Dunfield's NST program. NST allows you set the COM parameters for anything you want, but expects an 8 bit transfer. It defaults to 8N1-9600, which is what I initialized the 8251 to on the IMSAI.

I'm just happy to have a reliable mechanism to upload disk images. The laptop is certainly more convenient because of its size.