Thursday, 20 August 2009

Modding an HP Proliant DL585 to take an EVE Zebu UF2

I am the proud "controller" of an EVE Zebu UF2 emulation accelerator (a big PCI card covered in FPGAs). One of its biggest selling points is their Transactors which allow you to present your design with the interfaces it would experience if it were real, completely abstracting away the PCI bus.

However when I say big I mean triple height and full length. It uses 64 bit PCI/66. (For those considering purchasing a UF4 card most PCs can't fit it as it is larger still).

So I need a computer to host it in!

Enter the HP DL585 - a lovely machine. Built as solidly as a tank and everything is terribly easily accessible either from the front or the top. Everything. At a push I think I could swap out the motherboard and be back up and running in 30 minutes from cracking the case.

The original engineers designed it for cable-less operation (and very nearly succeeded!) but the EVE ZeBu-UF needs power from a 4 pin molex (found on most pre-SATA HDDs).

So what to do? Spotting this SCA backplane and knowing that HDDs take 12V, 5V and 3.3V power I had my solution. Mod a molex connector onto the pins on the back of one of the SCA sockets.

Firstly I checked the specifications for the ZeBu: 25W at 12V which is a current of 2.08A. Secondly I checked the specifications of the SCA2 connector: Section 6.4.1 of the SFF-8046 standard specifies a surge current of 5A and a constant supply of 2.5A. This means that one socket can supply the necessary power.

However, several provisos first: This will void your warranty. The SCA-2 connector transfers power to the drive using several pins for each voltage (12V, 5V and 3.3V) to reduce their resistivity to high current. By design the clusters of pins supplying the same voltage are next to each other making it easier. Probe for the resistance between the pins you think are the right ones - it needs to be zero.

The mod requires soldering the little clusters of pins together with fine wire (get some strands out of a multistrand wire) and then attached the cables. Note - don't include the Precharge pins - wiring them to the rest of the supply could cause unexpected operation as they will no longer function correctly when you insert a HDD in the front. After you are done, check, double check and triple check. Use a magnifier/microscope to check the soldering. Clean the area of any bits of solder. Probe the resistivity again. This could be an expensive mistake if there is a problem!

Power on (fingers crossed) and bingo - 12V and 5V.

Here is a photo of the modded card in position:


...and a photo of the UF2 in the PCI bay (I have two power connectors just in case I can get another UF2 - wishful thinking I know):