smp
Veteran Member
Hello all,
I am happy to let you know that I finally have my IMSAI system working with a Z80 CPU, a full 64K RAM, a Northstar floppy disk controller, and two 5.25" floppy disk drives.
It's been a bit of a long journey. I am certain that a number of folks here can remember my posts over the past few years, as I tried from time to time to get this IMSAI stable and working. I've been convinced all along that the IMSAI chassis and front panel are good, but the S-100 boards have sometimes seemed stable, and other times seemed glitchy. It's a great pleasure to have things finally pan out.
Back when, I first tried to get up and running with a SD Systems Versafloppy II controller, but I ran into a lot of difficulties. Another time, I tried to get a Northstar floppy disk controller going, and again I ran into difficulties. Recently, I've been posting here and in the CP/M thread about my latest adventures, again with a Versafloppy II.
As I wound my way with my most recent attempt with the Versafloppy II, I found a mis-marked floppy drive cable that had me plugging it in backwards. I recall that the problems I encountered long ago were probably caused by that same cable. On top of that, I also discovered that I had a floating ground (essentially no ground connected) between the power supply and the floppy disk drive. This time with the Versafloppy II, the problem showed up as garbage characters being output to my terminal screen. I believe that this problem also showed up in my earlier try with the Northstar controller. That time, I could read floppy disks, but when I attempted to write to a disk, all I got was garbage.
So, in this most recent round of effort with this system, I achieved success with the Versafloppy II controller working with the VF diagnostic program provided by John Monahan on the www.s100computers.com web site. As I posted elsewhere, my floppy disk drives have trouble initializing disks with 128 bytes per sector, and the software development effort for me to create the code to handle 512 byte sectors for CP/M is a bit of a bridge too far right now.
Buoyed by that success, I dug my Northstar floppy disk controller out again and gave it a go. I assembled the source code for an early version of Northstar DOS, patched it for I/O through my system monitor, loaded it up and did a warm start. Got Northstar DOS running. Had problems, however, with trying to initialize disks. Northstar DOS not really running.
Then, I remembered that during my past attempt with Northstar, Glitch had helped me out and provided two Northstar boot disks, in trade for a few 10 sector hard sector disks. I remember that I ended up destroying one of them, but what about the other?
Well, the short story is that I dug out that master disk that Glitch provided, and I tried a cold boot, and, VOILA. I am up and running with Northstar DOS version 5.1. I've been able to initialize 4 disks, and copy the master disk 4 times, and all of them have no errors, and all of them boot properly.
I am up and running!
Just one more anecdote to complete this story. Long, long ago, I had the very first computer store in New Hampshire, Microcomputers, Inc. While I was in business, I sold IMSAI computer kits and assembled systems, and Northstar floppy disk add-on systems (among other S-100 equipment). One of the systems I sold to a fellow was an IMSAI with a Merlin video graphics interface and a Northstar floppy disk system. That system is the one I have dreamed of owning ever since then. Well, I don't have the Merlin video graphics interface, and I may never will, but I now have the system I have dreamed of for all these years. What a thrill!
Thanks to you all for all the help you have offered me over the years.
Thanks for listening.
smp
I am happy to let you know that I finally have my IMSAI system working with a Z80 CPU, a full 64K RAM, a Northstar floppy disk controller, and two 5.25" floppy disk drives.
It's been a bit of a long journey. I am certain that a number of folks here can remember my posts over the past few years, as I tried from time to time to get this IMSAI stable and working. I've been convinced all along that the IMSAI chassis and front panel are good, but the S-100 boards have sometimes seemed stable, and other times seemed glitchy. It's a great pleasure to have things finally pan out.
Back when, I first tried to get up and running with a SD Systems Versafloppy II controller, but I ran into a lot of difficulties. Another time, I tried to get a Northstar floppy disk controller going, and again I ran into difficulties. Recently, I've been posting here and in the CP/M thread about my latest adventures, again with a Versafloppy II.
As I wound my way with my most recent attempt with the Versafloppy II, I found a mis-marked floppy drive cable that had me plugging it in backwards. I recall that the problems I encountered long ago were probably caused by that same cable. On top of that, I also discovered that I had a floating ground (essentially no ground connected) between the power supply and the floppy disk drive. This time with the Versafloppy II, the problem showed up as garbage characters being output to my terminal screen. I believe that this problem also showed up in my earlier try with the Northstar controller. That time, I could read floppy disks, but when I attempted to write to a disk, all I got was garbage.
So, in this most recent round of effort with this system, I achieved success with the Versafloppy II controller working with the VF diagnostic program provided by John Monahan on the www.s100computers.com web site. As I posted elsewhere, my floppy disk drives have trouble initializing disks with 128 bytes per sector, and the software development effort for me to create the code to handle 512 byte sectors for CP/M is a bit of a bridge too far right now.
Buoyed by that success, I dug my Northstar floppy disk controller out again and gave it a go. I assembled the source code for an early version of Northstar DOS, patched it for I/O through my system monitor, loaded it up and did a warm start. Got Northstar DOS running. Had problems, however, with trying to initialize disks. Northstar DOS not really running.
Then, I remembered that during my past attempt with Northstar, Glitch had helped me out and provided two Northstar boot disks, in trade for a few 10 sector hard sector disks. I remember that I ended up destroying one of them, but what about the other?
Well, the short story is that I dug out that master disk that Glitch provided, and I tried a cold boot, and, VOILA. I am up and running with Northstar DOS version 5.1. I've been able to initialize 4 disks, and copy the master disk 4 times, and all of them have no errors, and all of them boot properly.
I am up and running!
Just one more anecdote to complete this story. Long, long ago, I had the very first computer store in New Hampshire, Microcomputers, Inc. While I was in business, I sold IMSAI computer kits and assembled systems, and Northstar floppy disk add-on systems (among other S-100 equipment). One of the systems I sold to a fellow was an IMSAI with a Merlin video graphics interface and a Northstar floppy disk system. That system is the one I have dreamed of owning ever since then. Well, I don't have the Merlin video graphics interface, and I may never will, but I now have the system I have dreamed of for all these years. What a thrill!
Thanks to you all for all the help you have offered me over the years.
Thanks for listening.
smp
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