Build a SATA hard drive switch to boot multiple operating systems!
If you have a motherboard with at least two SATA hard drive connectors and have at least two SATA drives, you can build a low-cost physical switch to select multiple operating systems. Once you build and install the switch, all you have to do is select a switch position before starting your PC and your computer will automatically boot to the selected drive. It works by switching only the power between the drives. In order for this to work, you need to enable booting to your SATA drives in the BIOS (CMOS Setup). Also, you should not have any IDE hard drives connected. When you boot your PC, the drive that is selected by the switch is the only drive that will have power. Because all SATA drives are masters, the BIOS will see this as the only available drive and will automatically boot to it.
I have used software boot commanders (Acronis, Grub, boot.ini, etc.) in the past but have had my share of problems with boot partitions becoming overwritten and /or corrupt. I also didn't like the other option; going into CMOS setup and changing the boot order each time I wanted a different OS. Switching the drive power has many advantages. Each drive is totally independent so you can format any drive without affecting any of the other drives. Drive lifetime is extended and power supply load is reduced because the unselected drives are not powered up.
So, how do you build this switch? For my own use, I built a switch for three drives. I bought a four-pole, three position rotary switch from Newark. (Do a search for Newark Part Number 81F1014.) I already had three standard hard drive power (molex) to SATA power adapter cables. You can get them at most computer shops or at NewEgg. (Search for Sata Adapter.) I used some wire to lengthen all the power adapter cables so they could connect to the drives regardless of where I mounted the switch on my case. You will also need some solder, a soldering gun, electrical tape, a 1/4" knob to mount on the switch, and (optionally) some way to measure continuity between the pins of the switch. (Any multimeter will work fine for continuity checking). If you use the exact same Newark part that I did, you can get by without continuity checking.
Caution! If you wire up the switch incorrectly it is possible that you will damage your power supply and/or your hard drive, and possibly lose any data on your hard drive!
Step 1. Cut the power adapters and extend the length of the wires.
I cut up a couple of Sata power adapters to make the necessary plugs. You will need one male Molex power plug to connect to your power supply and three Sata power plugs to connect to your Sata drives.
The photo above shows one of the power adapters that I cut up. It is a single Molex-to-dual-Sata adapter. You will need to cut up a second adapter to get a third Sata plug. Next, you need to lengthen each wire on each plug. I suggest you make each wire about 2 feet in length. I made mine a bit shorter and one of the Sata power connectors barely reached the bottom drive in my full-tower case. Solder the wires together and wrap the connections in vinyl electrical tape or shrink wrap. I used shrink-wrap on mine.
Step 2. Solder the wires to the rotary switch.
I have received many comments that switching the ground wires is unneccesary. This is true. I connect the ground wires to the switch to make a neater-looking switch. Otherwise, you have to "Y" out the ground wires. Also, some have said that it is not a good idea to switch ground wires. I must emphasize that YOU SHOULD ONLY SWITCH THIS SWITCH WHEN THE COMPUTER IS SHUT DOWN! Then you boot the PC afterwards! That being said, I have revised the schematic to tie the ground commons to the three switched positions for each ground wire. So if you are using the same switch that I am, solder a jumper wire on the switch connecting common pin B to outer ring positions 4, 5, and 6. Likewise, tie a jumper wire between common wire C and switch positions 7,8, and 9. Now you are ready to begin connecting the wires.
If you are using the same switch from Newark that I used, refer to this wiring diagram.
Pins A,B,C,and D are the common poles that will be hooked up to the 4-pin male Molex power supply connector. Each common pole will switch to a different terminal on the outer ring when the switch knob is turned. For example, if the switch is in the first position (full CCW), there will be continuity between Pin A and Pin 1, Pin B and Pin 4, Pin C and Pin 7, and Pin D and Pin 10. The wires going to the first Sata power connector will be connected to pins 1, 4, 7, and 10. The wires going to the second Sata power connector will go to pins 2, 5, 8, and 11. The wires going to the third Sata power connector will go to pins 3, 6, 9, and 12. You still need to refer to my schematic to get the correct colored wires hooked to the switch.
Here's where you will need a multimeter if you have a different switch than the one I used. Set the multimeter to Ohms and X1 scale if you have an analog meter. If you have a digital meter, just set it to Ohms. Most rotary switches have the common poles in the center. These common poles will be switched to different positions on the outer ring of the switch, depending on which position you have the knob turned. First, solder the power supply (Molex) connector to the four common poles. You next need to look at the schematic diagram. Once you have the Molex connector soldered to the common poles, you should turn the switch shaft fully counter-clockwise. Using your Ohmmeter, check for continuity (low resistance) between the common pole where the yellow wire is attached and the terminals on the outer ring. When you find the correct terminal on the outer ring, solder the yellow wire on one of the Sata power cables to that terminal. Next, check for continuity between the red wire common pole and the outer ring. Solder the red wire on the same Sata power connector to that terminal. Next, find the black wire that is next to the yellow wire on the molex connector. Check for continuity between where that wire connects to the common pole and the outer ring. Solder the black wire that is the closest to the yellow wire on the Sata connector to the terminal on the outer ring. You now only need to solder one remaining black wire on the first Sata connector to the outer ring of terminals. Find where the black wire that is next to the red wire on the molex connector connects to the switch common pole. Check for continuity and solder the remaining black lead (it should be the lead farthest from the yellow wire on the Sata connector) to the terminal on the outer ring. You now have the first Sata connector wired. Now, turn the rotary switch one click clockwise and begin wiring the second Sata power connector, starting with the yellow wire. Follow the same sequence of steps as you did for the first Sata connector. Finally, rotate the rotary switch one more click clockwise and wire in the final Sata power connector.
Step 3. Mount the switch on your PC and attach the power cables.
I mounted my switch in an old CDROM drive that I had taken the guts out of. You can mount it anywhere you want, as long as the wires are long enough. Drilling a hole in one of the plastic drive bay covers would work too. You should wrap some vinyl electrical tape around the switch terminals before mounting the switch to avoid shorting them out on anything metal. I labeled the individual Sata power cables 1, 2, and 3 according to their switch position.
The finished product.
Connect the molex plug to an unused power supply connector and connect the Sata power connectors to your drives. Don't forget to hook up the Data cables for your drives to the motherboard also!
Step 4. Check that booting to Sata drives is enabled in BIOS.
If your motherboard has both IDE and Sata connectors, you may have to enable the Internal SATA Interface in the CMOS setup program. My ASUS motherboard is several years old and has only two SATA connectors. It also has two IDE connectors. I am only using two SATA drives on my computer, with the third switch position unused.
On my PC, the BIOS calls the two SATA drives the third and fourth IDE Masters. In the screen below, I have my SATA switch set to the second position. The drive that is getting power is the second Sata Drive, so the fourth IDE Master is detected.
Below, the Boot Order screen shows the detected drive as the hard drive option. You can still boot to a floppy, CD-ROM, or DVD-ROM drive when using the SATA switch.
Save the CMOS setup and you are done! If you have any trouble setting up your PC for the Sata Switch, you can e-mail me at cmorse0021@msn.com. I will try to answer as many as possible. There are other options you can try if you want to build a custom SATA switch. For instance, you can wire two SATA power plugs in parallel if you want to use Raid 0 or Raid 1 at each switch position. On my best PC I am currently running Vista with Raid 0 on switch position one and Centos 5.1 on the second switch position.
Also, as many people have pointed out, you can use a double-pole double-throw toggle switch if you only want to switch between two drives. You only need to switch the red (5V) and yellow (12V) leads because you don't need to switch the grounds. You just "Y" out each ground wire from the molex power supply connector to each drive.
At least one reader has sucessfully used a non-switched SATA drive as a non-bootable, backup/storage drive while using a SATA switch on two other drives. This will not work if your backup drive is an IDE drive. The PC will preferentially boot to the (always on) IDE drive. If you need a backup or storage drive, I recommend using an external USB drive instead of a non-switched drive when using a SATA switch.
If you don't feel comfortable building a Sata Switch yourself, I can build one for you.
