So you have a spare set of Mac Pro parts laying around, or wanna trick-out a Mac Pro with some modifications? While in the process of building my own Mac Pro 1,1 -> 2,1 project working on getting a RocketRAID 2720SGL going in El Capitan, I realized I didn’t really have a spare SFF-8087 (36-pin Mini SAS connector used on the Mac Pro 1,1/2,1 logic board) cable – so I made use of what I had.

(Pictured: The completed, modified adapter)

The Process

Upon inspecting the inside of the Mac Pro, I realized the Drive Bay wiring harness (a.k.a. the hard drive “backplane”) had the power connector quite close to the mini-SAS connector.. but the mini-SAS connector on the upgrade PCIe RAID controller card is on the other side of the computer.

(Pictured: A Mac Pro 1,1 logic board with the drive bay wiring harness, rest of Mac removed.)

Without an SFF-8087 to SATA/SAS cable and a power source to the drives, there’s no way to test a hardware RAID card in any capacity other than it registering/showing up on your Mac. In this situation, there are a few options:

• 1 – Leave the existing wiring harness inside your Mac Pro unmodified, only unplugging the logic board connectors, but you’ll need an adapter: An SFF-8087 extension male to female cable – lets you keep the power plugged into the logic board, only running a cable to the PCIe card.
  .
• 2 – Get an SFF-8087 to SATA/SAS cable + power adapters, leaving everything as-is.
  .
• 3 – Modify the existing internal OR spare wire harness, adapting the power rails to Molex or SATA while the cable remains plugged into the RAID card.

(Above: A RocketRAID 2720SGL with the unmodified spare plugged in.)

Power connector pinout

Getting started

In the box of PCIe power cables + adapters, I still had a molex adapter so I figured power could be drawn from the optical bay. Later I dig back into here for the PCIe 6-to-8-pin adapter.

On the molex adapter (side highlighted below), I carefully unsheathed the pins from the plastic housing, crimped them flat with pliers, and very carefully cut the flattened pin vertically so it can plug straight into the mini 8-pin PCIe connector.

Luckily everything went smoothly, the modified pins are snug. I took a spare ASUS PCIe 6-to-8-pin adapter from the box, pushed the pins out, cut the individual plastic pieces, and sleeved up the wires to prevent electrical issues. Since it’s all so compact the plastic doesn’t slide around, but I’d like to get more than just clear duck tape to keep those in place. It’ll do for now.

Connecting it up

In this example, I have a RocketRAID 2720SGL in Slot 3, with the SFF-8087 ports facing toward the front of the machine. The Mac Pro cable is sturdy and less malleable than your average cable – be careful not to bend too much.

In this test I used a SATA III Corsair Force GT 240GB SSD, connected it to “Bay 4” since the molex was adapted to the bottom row of the 8-pin connector. Combined together with a standard RocketRAID 2720SGL and modified kexts for El Capitan, this Corsair fired right up.

Testing it out

Works as intended, including desktop HDDs. If you’re powering solely SSDs off of all 4 connectors, a single Molex connector from the optical bay of the Mac Pro would do just fine. If you’re powering more than two 3.5-Inch desktop HDDs, I would recommend using two Molex connectors – one for each row of the 8-pin plug.

For a singular SATA III SSD on a Mac Pro 1,1 or 2,1, 477 MB/s read + 388 MB/s write is not bad at all! Faster already than the Apple RAID card, with far more room for expansion and performance. This card in particular auto-adjusts based on the device plugged in, and does have x8 lanes available to it – earlier when I had a single HDD or a SATA II SSD plugged in, only x1 lane showed up for this card. In any case, this is very promising!

.

In Conclusion

When putting together an earlier classic Mac Pro (from 2006-2007) and get a RAID card upgrade, repurposing an existing wire harness can save you money, whether it’s the one inside the Mac Pro or one you’re not using.

Now we know this works, I wonder, what could be done with such a configuration? First order of business is to cleanup the wires – that’s for a future article. High write speeds are nice especially on this machine, but can rEFIt or another bootloader boot OS X El Capitan off this RocketRAID? I’ll need to dig into this some more. I can’t even begin to imagine how fast my old SSD RAID0 array configuration from 2017-18 would’ve been on this card, rather than using the onboard SATA II then.