Mike's PCjr Page

If you do this, I will be watching from the sidelines, and would like to "follow along." I wish I could say I would be an active participant, but with real life going on, I think that is a commitment I cannot make. I had been thinking that it would be good to learn some assembly after Harg...

Chuck, thanks, I follow what you are doing with the drive select.

Thanks, jscrow also. I have been looking for a good paint match for a project I am thinking of. (I am not as bold in my color choices as Chuck!)

I had to go back and look carefully for that jumper. Your wire color matches the board traces very well.

Seriously, how many floppy drives are you going to put in that thing? I count 4 so far. Are you stacking your floppy boards to use as a drive selector?

I've been following your discussion on your 3flop board Chuck. (In this thread and others.) Looking at the schematic, if I follow it right, you can use jumpers (or a switch) to change the assignments of up to three floppies. Do I have this right? For your Kings Quest copy, you did this without reboo...

As I was booting a full blown modern operating system to write zeros to a single sector of a drive, I was thinking "There must be a way to do this with debug." Now I know!

I got it to boot off the SD card. I finally put all the clues together. The SD Card I had has a deficient MBR. In fact, it is all zeros (no executable code), with the exception of the partition table. So, there is nothing to start the boot process. However, because there is a MBR present, FDISK will...

I seem to remember reading about the "fdisk /mbr" command somewhere in this forum before. Looking at some on-line references, it seems like the switch appeared at DOS 5. I can't remember if I tried that command with DOS 3.3 or not. I think I did and got an error message and that's why I wa...

I am also having the boot problem with an SD to IDE adapter not booting. I am using this SD adapter: https://www.amazon.com/gp/product/B07G29TZPS with a store brand 32 GB SD card from Microcenter. I am running DOS 3.3. Like kotto7877, I can only use the drive if I boot from a floppy. If I try to boo...

The monitor was always my working assumption.

Which is better than the PCjr itself, I think.

I was hoping the answer was going to be more along the lines of: "We've seen this before. Replace cap C102 in the monitor and all will will be well." One can always hope, right?

I am having display problems with my PCjr and I am hoping that the collective wisdom here can point me in the right direction. Machine boots and runs fine - for a while. After a period of time (approx 30 to 45 minutes - not exactly timed) a reboot will produce a scrambled screen as shown: https://ww...