• Please review our updated Terms and Rules here



Veteran Member
Aug 14, 2010
If you have an AT class computer with an onboard battery that is dead or about to die and no way to replace it, then this might be something for you. It's a simple boot sector program I made for my Wang Microsystems PC 250/16. I believe it should work on any AT computer but I haven't tried it on anything else but the Wang (both at 8 and 16 MHz).

I often see posts on this forum where people are having battery related problems so I figured this piece of code may ease someones life, maybe even save people from having to trash an otherwise working computer.

In order to be able to boot the computer normally (from harddrive) we need to restore the BIOS Setup configuration to the computer's CMOS, either by running the actual Setup program and redo all the settings, or even better, by running a program that restores a previously made backup of the configuration. This is the way I used to do it. However, it requires that the computer can boot an operating system (DOS) before we can run programs to restore any backups.

Now, as I'm sure you already know, booting even a simple operating system like DOS can be a challenge if the battery is bad. Without any battery at all the aforementioned Wang acts completely random as to what version of DOS will succeed to boot. Sometimes MS-DOS 6.22 won't work but DR-DOS 7.03 will. Sometimes it's the other way around. A couple of times neither of them worked and I've had to resort to some Compaq Setup/Diagnostics diskette (OEM version of MS-DOS 6.20 I believe) to get it to boot. I don't know if this is a quirk with this particular machine or if it applies to others as well, but in any case, as you probably can imagine, hunting for a floppy that works quickly gets tiresome. So after noticing that DOS always starts to boot before hanging, I realized that I could just write a boot sector program that automatically restores the configuration. This is the result. I hope someone has a use for it. The source with instructions are in the attached file.

View attachment wangboot.zip