I often browse classified for some unusual thing that I can convert to something usable. One of these things I found was a few years old HP rack servers - HP DL380. A lot of them are offered in price under 50 USD. So I decided to buy one, with these specs:

2 x E5540 Xeon processor
16GB RAM
2x 147GB SAS HDD
750W power supply

After some reading I found it can be converted in quite powerful workstation or even gaming PC. What I needed for that?

Add SSD drive
Add GPU
Upgrade CPUs
Silence it. The HP server is really really LOUD, because of fans. I had to find way to make it more silent.
Install Windows 10

Supplies

HP DL380 G6 Server
Any SSD Drive >= 128GB
PCIe SATA 3 controller
Two low RPM pwm fans
Some ventilation pipe ;-)

Step 1: LSI SAS2008 and SSD Drive in HP DL380 G6

HP DL 380 G6 comes with built-in raid controller HP SmartArray P410i. I put SSD drive to disk enclosure and controller sees it properly, but performance was terrible. Exactly as many wrote on the internet.

So I need a SATA 3.0 controller on PCI. I bought DELL Perc H310 for 15 USD. It's based on LSI SAS2008, and can be found also under other names like IBM M1015 or just LSI SAS 9211-8i.

To gain great performance on it I had need to remove RAID features out of this. I found great post how to flash firmware in so called IT mode. I followed commands in this tutorial, but downloaded firmware and BIOS directly from the DELL website.

Flashing BIOS is important, as SSD is my boot drive. Without BIOS, you will not be able to boot from that drive (but then Windows will see drive as additional one).

Some important hints:

If you want to flash IT firmware make it the only PCIe card in your computer during programming. Otherwise it may not work and write message like "Firmware Download Failed!".

Then I had to use specific version of sas2flsh utility (p14 exactly), that can be downloaded from Broadcom website. Other versions gave me some errors too.

The SAS2008 comes with two SFF-8087 connectors, so one also needs SFF-8087 to SATA cable. And another SATA power connector - see next step.

After all, my server boot up from SSD drive. Installing Windows 10 on it was as simple, as boot from USB flash drive. All drivers are built-in in Windows 10.

Step 2: 10 Pin to 6 Pin and SATA Power Cable HP DL380 G6

HP DL380 G6 has a 10 pin connector on motherboard that can supply power to some additional devices that may be installed. I used it to power SSD drive and newly installed GPU.

This cable can be bought online (even on aliexpress). I bought one from local classifieds for 10 USD.

There are two types of power supplies in this server - 450W and 750W. My comes with 750W so it is enough to power modern graphic card. Probably you may also install two 450W power supplies to achieve enough power.

Step 3: Installing GeForce GTX 660 GPU in HP DL380 G6

There can be six PCIe cards installed on this server, through raisers. My server comes with two raisers and each has one PCIe 8x and two PCIe 4x slots.

The PCIe 8x is good choice to install GPU. You can put GPU with PCIe 16x interface, as they are compatible. You may read the benchmark, that shows that it doesn't influence the performance at all.

Important factor when selecting a GPU is it's size - there is not so much of it in the server. I've chosen GeForce GTX 660 GS from Gainward, as it's quite small and powerfull enough for my needs.

As you may see in the picture - there may be need to modify case to allow all connectors to be available. I'm using only one DVI only.

Additional power to GPU is connected by 10pin to 6pin cable I described in previous step.

Step 4: Connect Silent Fan to HP DL380 G6

Fans in HP DL380 G6 are really loud. It was designed to work in server rack, not to use as workstation. It gets even louder when you install any PCIe card or non HP hard drives - as the motherboard gets no temperature data from them it will make running fans in max speed.

I decided to remove original fans and replace them with two 140mm low rpm fans, that are really quiet.

When you remove original fans, the server will shut down itself just after start. You cannot change that bahaviour in BIOS etc. But there is an solution. I disassembled all original fans. Cut the green, red, black and yellow cable. And connect together yellow and all blacks. Connecting yellow to black (GND) is a signal that motherboard needs to think, that fan is installed. And that's it - it will run. There is no need to make any more complicated emulators :-)

Then I also needed to connect my new fans. So I connected them to black and red cables as fan power supply, and green as PWM signal. Motherboard adjusts fan speed based on temperature reading.

UPDATE: Read the comments below for info about PWM cable.

Remember to isolate connections!

Step 5: Install 140 Silent Fan in HP DL380 G6

I found ventilation pipes in my local DIY store,that suit exactly in place where old fans were. And it makes air flow in identical direction so both CPU and other components are cooled properly.

Look at the photos to see how I installed them.

After this was installed, together with GeForce GTX 660 i run a stress test for this machine, to make full power of CPU and GPU. Temperature of CPU was max 60 Celsius degree. On "office work" it is below 30. GPU is around 40-50.

So this works really well and noise is at the level like any desktop PC.

Step 6: Final Thoughs on Converting HP DL380 G6 to PC Workstation

There are some pros and cons of this construction.

Pros:

You get great performance for your money. I've paid:
1. 50 USD for the server with 16GB RAM and two 146GB SAS drives (used)
2. 20 USD for two six core CPUs Intel Xeon X5670
3. 15 USD for SSD controller and SATA cable (used)
4. 20 USD for 240GB SSD drive (new)
5. 10 USD for 10 pin power cable (used)
6. 20 USD for the fans and pipes (new)
So for total of 135USD I've got performance better than classic desktop i7-8700K. So it's like.. 60% bargain ;-)
You may buy A LOT of cheap RAM to this server. It uses DDR3 ECC ram. It's cheaper than traditional ones, as there are offers of 15USD for 4x4GB. And you have 16 slots of ram to fill :-)
Windows 10 contains all needed drivers build-in.
You have built-in raid controller with 8 hot swappable disks. You may put both SAS and SATA 2,5" drives there (eg from laptop). It's great for storing multimedia, backups etc.
Easy to buy spare parts. This servers are really popular, so you can buy any spare part like power supply, cables, raisers, hard drive bays really quick and cheap.

Cons:

It's heavy and hard to hide in a room. Really, it's like 20kgs.
It boots slow because of all diagnostics it makes during the boot. It takes almost 4 minutes.
It needs PS/2 keyboard connected to operate in BIOS. Then in Windows you may use USB keyboard.
There is no built-in sound card. I'm using USB one.
There is no build-in wifi adapter. I'm using USB one. (but there are four 1GB ethernet adapters)
There are only four USB 2.0 connectors. You may need to instal PCIe card with more USB 3.0 connectors if you need them (it's additional 10USD to spent).