How to make JrIDE boot from compact flash (a 1,2,3 guide)

Post Reply
Posts: 29
Joined: Fri Mar 20, 2020 10:01 pm

How to make JrIDE boot from compact flash (a 1,2,3 guide)

Post by toddvernon »

I've been on my PCjr quest for about a month now. I got a machine running and booting off floppy thanks to Chuckphd53 but I wanted to get it booting from hard disk. I followed a lot of the stuff on Mikes's board ... 7&start=10 and watched Adrian @ "Adrian's digital basement" fire his up and googled a TON of stuff. It took me the better part of the weekend and was a little frustrated how easy it "eventually was" to do


1) Get a 40 pin IDE to Compact flash adaptor. (not a 44, lesson learned), I paid $6 on eBay.
2) Hook up power as Adrian did on the video above.
3) Get a compact flash card. While there is a ton of discussion out there that some work and some don't, I'm not so sure, I used a 15GB Sandisk II
4) Plug it all together, watch Adrian fail at having the adaptor backward, I did that also, it goes together opposite of you would like.
5) Boot on Dos 3.3 Floppy, I used Dos 3.3 (thanks Chuckphd53 for sending)
6) Change to Dos 3.3 floppy #2 that has the "debug" dos command.
7) Enter the following short assembly program (don't be scared) and the "g" command will execute it. Basically this wipes the partition table on the compact flash card. This is surprisingly hard to do with other nicer utilities. The PC "fdisk" won't do it, and the Mac diskUtil won't without installing a new partition. Do this instead, it's EASY.

A> debug
<address debug will add> mov ax, 309
<address debug will add> mov cx, 1
<address debug will add> mov dx, 80
<address debug will add> int 13
<address debug will add> int 20

7) Reboot, and boot from Dos3.3 #1 floppy again
8) Enter "fdisk" and create a primary dos partition
9) Reboot again tp Dos 3.3 (fdisk will make you)
10) Enter "format C: /s". This will format the flashcard and install the boot loader and ""
11) Enter copy a:*.* C: This will copy all the other dos commands to the hard disk.
12) Celebrate your success at building a bootable compact flash card!

Part of the fun of these computers is the journey. But to be honest, sometimes your just not sure you are going to get there.

This got me there!

Post Reply