Commodore’s 1541-II disk drive has a pair of DIP switches on the back to let you change its device number. DOS and Windows computers use drive letters to address its disk drives (usually A: and B:). Commodore used the numbers 8-11 to address them. Here’s how to set the 1541-II DIP switches so you can run more than one drive.
The switches are at the back of the drive, in between the ports to connect to the computer and the port to connect the power supply.
Here’s how to set the switches for any one of four drive numbers:
- 8: Both switches up
- 9: Left down, right up
- 10: Left up, right down
- 11: Both switches down
When you change the switches, use a small screwdriver or a toothpick. Never use a pencil. If you break off the tip of the pencil, the tip can potentially cause a short circuit inside the drive.
Note that you won’t harm the drive by changing the switches with the power off, but the drive only reads the switches at power up. To make the changes take effect, you have to cycle the drive’s power. It’s better to change the switches with the drive’s power off to avoid confusion. But it’s also much easier to reach the switches with the drive powered down and disconnected.
After you change the device number, it’s not a bad idea to mark the drive with a piece of tape and its number.
To change previous models of the 1541, you had to cut jumpers on the drive’s circuit board. So the 1541-II makes an ideal secondary drive. If you have an earlier 1541, use it as drive 8 and use a 1541-II for drive 9.
It shouldn’t strictly matter how you connect the drives, but Commodore recommended plugging drive 8 straight into to the computer. Plug drive 9 into drive 8. If you need help connecting them, see my earlier post on connecting Commodore disk drives.
Most software expects your primary drive to be drive 8 and your secondary drive to be drive 9. But strictly speaking, as long as you set your drives to different numbers, they will work together.
Mixing drive types
You can mix any combination of drive types as long as you give them a unique device number. I’ve done multi-drive setups with an original 1541, 1541-II, 1571 and 1581 before. Mixed-drive setups were very common among BBS operators during Commodore’s heyday.
That’s all you need to know about 1541-II DIP switches. Enjoy your Commodore!