Tuesday, 19 August 2014

IBM x3500 SAS Backplane Pinout

IBM x3500 SAS Backplane Pinout

You can get these backplane boards fairly cheap on ebay these days.  Even if you don't have the server it belongs do, they could still be useful for DIY storage projects. The IBM FRU is 44E8783. There are likely other similar IBM parts that use the same pinout, but no guarantees.
Unfortunately as far as I can tell, nobody bothered to document the cabling for them!  As luck would have it, I still have a working one, so I was able to map out the power cable with a multimeter.

This is just a regular backplane, not a SAS expander - one SFF-8087 connector for 4 drives.  The data connector is standard, it's just the power cable that is strange.  It looks similar to an ATX 24 pin power connector, but smaller.  If you are buying one to use in a different device, make sure it comes with the power cable - you may not be able to easily find the right connector.

I measured this by removing the cable from the backplane and measuring the voltage on each pin, with the black probe on the metal of the case (ground).  The picture shows how I numbered the pins.



  1. Good work my friend. Much appreciated. This is good knowledge to have. You are the first to document it. I have searched for a week. I am going to PING BACK this article. There are a slew of tech nerds out there asking for this information. Thanks again.. James Black CSE

  2. Interestingly, 3.3 volts is actually used, or as a backup for both type connectors on ordinary sata drives

  3. Fantastic. Truly a delight to read. Limitless thanks.
    Never having the PSU had exhaustively experimented but with numerous wires and thinking the color would be truly representative of the value completely bamboozled.
    Have you ever looked at the Sun Netra 240 dual 2.4 inch sata pinout??? 1-8 pin all black..?

  4. Does anybody know if the pinout for an X3650 SAS backplane (IBM 44W3110) is the same? The plug looks the same (only the cable is shorter). The pins 1-4, 9-16 and 21-24 seem to be the same. I am just not sure about 5-8 and 17-20. The pins which should be ground do not connect to PCB ground neither on the psu nor on the backplane side. To bad that I don't have the PSUs for testing. Can anyone help? Has anyone tested this pinout and is it working?