Mike's PCjr Page

Yep, mission accomplished!. I've installed IBM-DOS 5.0 into a 64Mb CF card.

First I created a plain bootdisk using a virtual installation of IBM-DOS using VMware, then patched it and added to the disk the needed tools like FORMAT, FDISK OR DEBUG. Once the PCjr booted, I created a 8MB primary DOS partition in the previously erased CF card, set as active partition and rebooted. After booting again using the bootdisk, FORMAT C: /S, FDISK /MBR and copied some files like AUTOEXEC.BAT, CONFIG.SYS, JRCONFIG.SYS and such into the formatted partition C:. Last but not least, patched again the newly created C: drive following the same guide applied before (remember that C: drive is 2 when using DEBUG) and after a new reboot without the bootdisk inserted, Hop!, drive C: booted flawlessly into a IBM-DOS 5.0 prompt

Next step: Add support for 720KB disks and try to make a full install of IBM-DOS 5.0

Btw, I'm getting now 605872KB free for apps, is there a way to get some more free memory using jrconfig or any other trick?. I'm not sure yet if I've disabled the ramdrive and I don't want it...

I take it that the patch procedure that is posted is correct then?

591KB free isn't bad. If you want the RAM disk memory back look at the -s option on jrconfig, but getting rid of it will make your machine quite a bit slower. Also, are you running the latest BIOS ? (Just a week or two old ...)

Yep, indeed, it's correct. It turns out that I simply needed a bootdisk. The original IBM-DOS 5.0 installation disk didn't work for me. Patching the DOS 5.0 boot disk was a breeze.

About the RAM disk, is it auto-magically used by some part of the DOS or jrconfig?, if it's really been used and it can speed up the OS (in fact, jrconfig displays a suggestion about raising the RAM reserved) I'll keep it.

I suposse that DOS 3.3 will use a bit less RAM; but the benefits of DOS 5.0 are greater.

jltursan wrote:Yep, indeed, it's correct. It turns out that I simply needed a bootdisk. The original IBM-DOS 5.0 installation disk didn't work for me. Patching the DOS 5.0 boot disk was a breeze.

About the RAM disk, is it auto-magically used by some part of the DOS or jrconfig?, if it's really been used and it can speed up the OS (in fact, jrconfig displays a suggestion about raising the RAM reserved) I'll keep it.

I suposse that DOS 3.3 will use a bit less RAM; but the benefits of DOS 5.0 are greater.

Nah, if it's set up as a RAM disk, it's just a RAM disk. It'll only be used if you decide to put something on it. If you're not going to use it, you can set jrconfig to not assign a drive letter, and it will just prevent anything from using that region of RAM. There's also an option to recover all the RAM, but like Mike said, it will make your system slower. It sounds counter-intuitive that increasing the available RAM would slow down the computer, but the problem is that the RAM disk takes up a portion of 'slow' RAM (meaning the RAM internal to the PCjr, which has a slow refresh cycle). When this RAM is freed, programs will take up the slow RAM before they take up the fast RAM on the upgrade, causing the entire system to run as if it is running in slow RAM. When this RAM is blocked off or used as a RAM disk, only DOS will run in slow RAM, and the speed gained in all other programs is very apparent.