524 lines
19 KiB
Markdown
524 lines
19 KiB
Markdown
+++
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title = "BC-Zero - Board Testing"
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summary = "From an old mining board to a console and AI server"
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date = "2026-11-08"
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tags = ["BC-250", "PS5", "Unlock", "BIOS", "CPU", "GPU"]
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categories = ["Projects"]
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series = ["BC-Zero"]
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series_order = 1
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+++
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On February 5th, [Soffio](https://t.me/Soffioo), a friend and fellow
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[LUGMan](https://lugman.org/) member, made me discover a peculiar board: the
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**BC-250**.
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The BC-250 is a board that comes from an [ASRock cryptocurrency mining
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rig](https://www.tomshardware.com/news/twelve-ps5-apus-power-asrocks-new-cryptomining-rig),
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which housed twelve of them.
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Inside each of these boards there's a *binned* chip derived from the AMD APU of
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the PlayStation 5, with 6 of the 8 CPU cores and 24 of the 36 GPU CUs enabled,
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along with 16GB of GDDR6 RAM **unified** between CPU and GPU, an M.2 slot (PCIe
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2.0x2 or SATA III), and just a few ports: two USB 2.0, two USB 3.0, one Gigabit
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Ethernet, and one DisplayPort. Power is supplied through an 8-pin PCIe
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connector.
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At first I wasn't really convinced, especially seeing a third of the CUs cut off
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and knowing that it's a board with a custom, partially locked chip (on top of
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the locked cores, some features like video encoding/decoding are missing),
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coming from cryptocurrency mining and with no support or community behind it.
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But the price was definitely interesting, and apparently this board has a very
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active community that works hard to squeeze 100% of its potential out of it on
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Linux.
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Things changed when, on the morning of May 30th, I got this message:
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And good old Soffio also pointed out that the AliExpress sales were about to
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start. Intrigued by the whole thing, I asked him if he could lend me his board
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for a few days, just to try it out and see what could be done.
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And *oh boy*, did this board convince me.
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## Step 0: Preparation
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One downside of the BC-250 is that it's not exactly *plug-and-play*. At the very
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least, you need to:
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1. Find a power supply that can ***really*** deliver at least 300W on the +12V
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rail, with cables that can handle all those amperes;
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2. Have a monitor with DisplayPort (or buy an adapter);
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3. Find a way to cool the damn thing;
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4. Flash the BIOS.
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My test setup was:
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1. The first "*el cheapo*" power supply I could find lying around (which "will
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surely be fine, it says 500W");
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2. A passive DP ➜ HDMI adapter;
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3. A portable air conditioner for cooling (it was summer and it was starting to
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get hot);
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4. A CH341 SPI programmer (which I already had).
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Not exactly the best setup for testing the board, but you work with what you
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have.
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## Step 1: Flashing the BIOS
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The [first step in the community
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documentation](https://elektricm.github.io/amd-bc250-docs/getting-started/quick-start/#step-1-bios-flash-critical)
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is flashing the BIOS. Without a custom BIOS you don't get essential features
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like dynamic VRAM allocation (remember, the 16GB of RAM are shared) and proper
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fan control.
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At first I installed the one recommended by the guide, the one by
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[TuxThePenguin0](https://gitlab.com/TuxThePenguin0/bc250-bios), but later on I
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discovered another BIOS, the one by [Forbidden
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Darkness](https://github.com/Forbidden-Darkness/AMD-BC-250-UEFI-v2.2-Firmware-Menu-Script),
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which, on top of unlocking the dynamic allocation menu, offers a selection of
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custom splash images and, most importantly, **unlocks all 8 CPU cores**.
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"*Wait, weren't they locked down?*" Apparently not enough.
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The APU has all cores on the silicon, they're just disabled via firmware. A
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similar principle also applies to the GPU CUs, but we'll get to that later.
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---
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The installation is even simpler and doesn't require a BIOS flasher: just copy
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the files from the `.7z` archive in the releases to a USB stick formatted in
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FAT32 and boot from it. The installer asks which splash image we want (the
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[`07`](https://github.com/user-attachments/assets/ca23ce6c-08ab-4293-9a70-0e55f66dc93c)
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is the best one, *imho*) and proceeds with the flashing.
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{{< alert icon="triangle-exclamation" cardColor="#e6d237" iconColor="#1d3557"
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textColor="#1d3557" >}}
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Flashing the BIOS is a dangerous operation. Make sure the board doesn't turn
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off.
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{{< /alert >}}
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Once the flashing is done, you need to reset all the BIOS settings. To do that,
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just unplug the power and bridge pin 2 and 3 of the `CLRCMOS1` header for a few
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seconds. Once that's done, we can put the header back on pins 1 and 2 and plug
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the power back in. By entering the BIOS with the `Del` key at boot we'll see a
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lot more options.
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First, let's make the VRAM allocation automatic. To do that, we need to go to
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`Chipset` > `GFX Configuration` > `GFX Configuration` and set `Integrated
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Graphics Controller` to `Forces`, then `UMA Mode` to `UMA_SPECIFIED`, and
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finally `UMA Frame buffer size` to `512M`.
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Then in `NB Configuration` disable the IOMMU (it doesn't seem to work on this
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board).
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Finally, we enable all the cores by going to `Advanced` > `MeiMeiDXEv3 Menu` and
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enabling everything.
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{{< alert icon="triangle-exclamation" cardColor="#e6d237" iconColor="#1d3557"
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textColor="#1d3557" >}}
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There's no guarantee that all the cores will work. Damaged cores could cause
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sudden crashes.
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To avoid that, we'll run a stress test on all the cores and check that no
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`Machine Check Exception` shows up in the kernel logs before enabling this
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setting in production.
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{{< /alert >}}
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Once the BIOS is properly configured, we're ready to install an operating system
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and test this board for real.
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## Step 2: Installing a OS for testing
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To do some CPU stress testing and run some tests on the GPU, I'll install Arch
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Linux.
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It won't be the final distro I'll install, but the choice isn't random:
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development for this board is bleeding-edge, and for now almost all the scripts
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assume you're running Arch or Fedora, so you have the latest package versions.
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### Testing the 8 cores
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First of all, let's test whether all 8 cores work as they should. To do that,
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install the `stress-ng` package and run a stress test:
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```sh
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stress-ng --cpu 16 --cpu-method all --verify --timeout 2h --metrics
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```
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Then we check that there were no errors with:
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```sh
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sudo dmesg | grep -iE "mce|machine check|hardware error"
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```
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If the kernel doesn't report any errors, we've just gone from 6 to 8 cores for
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free. If there is an error you can change which cores to enable from the BIOS.
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### Stress-testing the GPU
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Next, let's stress test the GPU to get a performance baseline before installing
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the governor or enabling all the CUs. To do that, I installed Furmark and ran
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the 1080p test.
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I'd say 70 FPS isn't *that* bad for the board *out-of-the-box*, but we can
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definitely do better, much better.
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---
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A small note I feel I should add: if during the stress test the screen goes
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black and the board doesn't respond in any way, check your power supply. The
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little foreshadowing I did in step 0 about the power supply is because during my
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tests I ran Ollama and completely fried the PSU since (apparently) it couldn't
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really handle the whole load on the +12V rail. I then bought the PSU recommended
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by the community on AliExpress, along with the board, the [Metalfish 500W
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FlexATX](https://elektricm.github.io/amd-bc250-docs/hardware/power#option-2-flexatx-psu-500w),
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and I haven't had any problems since.
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### Installing the GPU Governor
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By default the GPU always runs at 1500MHz: a governor lets you raise the clock
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when the GPU is under load and lower it when it isn't, to save power.
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We'll install `cyan-skillfish-governor-smu`, a community project that talks
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directly to the board's System Management Unit. It's also already packaged in
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the AUR, so to install it you just need to run:
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```sh
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paru -S cyan-skillfish-governor-smu
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systemctl enable --now cyan-skillfish-governor-smu
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```
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We can check that it works with:
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```
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$ cat /sys/class/drm/card1/device/pp_dpm_sclk # If it doesn't work, try card0
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0: 1000Mhz *
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1: 1500Mhz
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2: 2000Mhz
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```
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The first and last lines are, respectively, the minimum and maximum GPU
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frequency, while the middle line can change. The asterisk marks the frequency
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currently in use. An example under load:
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```
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$ cat /sys/class/drm/card1/device/pp_dpm_sclk
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0: 1000Mhz
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1: 1850Mhz *
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2: 2000Mhz
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```
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We should see the GPU automatically use a higher frequency under load and a
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lower one when idle.
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---
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**Small note**: unlocking the 8 cores affects how the SMU values are read. It's
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a known issue and we'll fix it later on, when we'll deal with the operating
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system. Without any fix, the frequency values are wrong, for example:
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```
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$ cat /sys/class/drm/card1/device/pp_dpm_sclk
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0: 1000Mhz *
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1: 4575Mhz
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2: 2000Mhz
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# Not a bad overclock for a chip that tops out at 2230MHz
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```
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With that said, let's run a stress test now, with the governor installed.
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Now that we can scale up to 1850MHz, our GPU manages to reach 83 FPS at 1080p,
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not bad!
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1850MHz is by no means the most this chip can handle, but for now we'll settle
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for it. For the curious, the frequency and voltage curves are fully customizable
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and live in `/etc/cyan-skillfish-governor-smu/config.toml`. With a bit of trial
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and error you can push the hardware to its limits while minimizing power draw,
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but we'll do that when we set up the final operating system.
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### Unlocking the 40 CUs
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As we said at the beginning, this board only exposes 24 CUs to the kernel, even
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though the PS5 has 36 and there are actually 40 on the silicon. We can verify
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this with:
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```
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$ sudo dmesg | grep active_cu_number
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[ 6.882856] amdgpu 0000:01:00.0: SE 2, SH per SE 2, CU per SH 10, active_cu_number 24
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```
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To test and then unlock all the CUs, we'll use [duggasco's
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repository](https://github.com/duggasco/bc250-40cu-unlock). The mechanism is
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similar to the core unlock: here too you just need to change a few values,
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because the CUs aren't locked at the hardware level, they're just disabled by
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the firmware.
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Two registers in the GPU decide how many CUs are active. What this script does
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is patch the `amdgpu` driver and write the right values into those registers
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while the driver starts up, waking up the disabled CUs.
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```
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$ git clone https://github.com/duggasco/bc250-40cu-unlock.git
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$ cd bc250-40cu-unlock/
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$ sudo pacman -S linux-headers vulkan-headers
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$ sudo scripts/bc250-enable-40cu-arch.sh build
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# Wait for the `amdgpu` module to be recompiled
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$ sudo scripts/bc250-enable-40cu-arch.sh enable
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```
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Once the BC-250 has rebooted, we can check that the patch worked using the same
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command as before:
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```
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$ sudo dmesg | grep active_cu_number
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[ 8.004012] amdgpu 0000:01:00.0: SE 2, SH per SE 2, CU per SH 10, active_cu_number 24
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```
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Apparently the script doesn't load the custom module automatically. That's not a
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problem: let's regenerate the initramfs and reboot manually:
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```
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$ sudo mkinitcpio -P
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$ reboot
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# Once it has rebooted
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$ sudo dmesg | grep active_cu_number
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[ 8.058999] amdgpu 0000:01:00.0: SE 2, SH per SE 2, CU per SH 10, active_cu_number 40
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```
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Much better!
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---
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Once the custom module is installed, we can move on to testing the CUs:
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```
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$ sudo scripts/bc250-cu-health-test.sh start
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```
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During the test the PC will automatically reboot twenty times. Once the PC stops
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rebooting on its own, we can see the test results with:
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```
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$ scripts/cu_map.sh
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BC-250 CU Map + Health
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SE0 SH0: ■■■■■■■■■■
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SE0 SH1: ■■■■■■■■■■
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SE1 SH0: ■■■■■■■■■■
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SE1 SH1: ■■■■■■■■■■
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40/40 CUs active, 0 harvested
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BC-250 CU Map + Health
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SE0 SH0: ■■■■■■✓✓✓✓
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SE0 SH1: ■■■■■■✓✓✓✓
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SE1 SH0: ■■■■■■✓✓✓✓
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SE1 SH1: ■■■■■■✓✓✓✓
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40/40 CUs usable (0 defective, masked)
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```
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Apparently I won the silicon lottery and have 8 cores and 40 working CUs.
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Hurray! 🎉
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If there had been any defective CUs I could have masked them using the
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`bc250-cu-mask.sh` script.
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---
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Running the last stress test with Furmark:
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We went from the bare board, without any additional software, running at an
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average of 70 FPS, to having a governor and all the CUs unlocked, with peaks of
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138 FPS, twice as much!
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Of course, this approach to unlocking the 40 CUs has a pretty obvious problem,
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especially on rolling distributions like Arch: you have to recompile the module
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every time you update the kernel. This is another problem we'll solve later on,
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when we stop using a test OS, but if after an update the GPU isn't as fast as
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before, it might be worth taking a look.
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### Sensors and Other Essential Configurations
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Once the essentials like CPU and GPU are sorted out, there are still a few small
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things to take care of, such as sensor management, fans, swap, VRAM split,
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etc...
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I could go on about it for hours, but I'll point you to the [community
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documentation](https://elektricm.github.io/amd-bc250-docs/), which is very
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thorough.
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What I'd like to do now is point out one thing: using the `sensors` command, we
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get very little data OOTB:
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```
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$ sensors
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amdgpu-pci-0100
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Adapter: PCI adapter
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vddgfx: 799.00 mV
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vddnb: 799.00 mV
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edge: +39.0°C
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PPT: 41.41 W (avg = 40.85 W)
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sclk: 1000 MHz
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k10temp-pci-00c3
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Adapter: PCI adapter
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Tctl: +41.6°C
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```
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To get more data we need the `nct6683` module (read-only) or `nct6687` (you can
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create custom curves with it, but it's *out of tree*). Since `nct6683` is
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already available, we can enable it with:
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```
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$ echo 'options nct6683 force=true' | sudo tee /etc/modprobe.d/sensors.conf
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$ echo 'nct6683' | sudo tee /etc/modules-load.d/99-sensors.conf
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$ sudo mkinitcpio -P
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$ reboot
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```
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After rebooting we'll see a lot more data:
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```
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$ sensors
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k10temp-pci-00c3
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Adapter: PCI adapter
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Tctl: +46.9°C
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amdgpu-pci-0100
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Adapter: PCI adapter
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vddgfx: 799.00 mV
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vddnb: 799.00 mV
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edge: +41.0°C
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PPT: 42.61 W (avg = 40.75 W)
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sclk: 1000 MHz
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nct6686-isa-0a20
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Adapter: ISA adapter
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VIN0: 800.00 mV (min = +0.00 V, max = +0.00 V)
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VIN1: 1.01 V (min = +0.00 V, max = +0.00 V)
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VIN2: 992.00 mV (min = +0.00 V, max = +0.00 V)
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VIN6: 1.39 V (min = +0.00 V, max = +0.00 V)
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VIN7: 800.00 mV (min = +0.00 V, max = +0.00 V)
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VIN16: 896.00 mV (min = +0.00 V, max = +0.00 V)
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fan1: 0 RPM (min = 0 RPM)
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fan2: 1709 RPM (min = 0 RPM)
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fan3: 0 RPM (min = 0 RPM)
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fan4: 0 RPM (min = 0 RPM)
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fan5: 0 RPM (min = 0 RPM)
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AMD TSI Addr 98h: +47.0°C (low = +0.0°C)
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(high = +0.0°C, hyst = +0.0°C)
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(crit = +0.0°C) sensor = AMD AMDSI
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Thermistor 14: +37.0°C (low = +0.0°C)
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(high = +0.0°C, hyst = +0.0°C)
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(crit = +0.0°C) sensor = thermistor
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Thermistor 15: +37.0°C (low = +0.0°C)
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(high = +0.0°C, hyst = +0.0°C)
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(crit = +0.0°C) sensor = thermistor
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pwm1: 64%
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pwm2: 64%
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pwm3: 64%
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pwm4: 64%
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pwm5: 64%
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intrusion0: OK
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beep_enable: disabled
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```
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## Step 3: Hardware Mods
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I want to remind you that for all these tests I was using Soffio's BC-250, just
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to see whether it was something I'd be interested in. And since I found myself
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pretty hooked I decided to get everything I needed from AliExpress.
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Luckily with the sales and also using TopCashback I managed to bring home
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everything I needed for less than €200. I then bought a couple of Arctic P12
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Pros from Amazon.
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Everything arrived on June 24th, so it was time to get to work on:
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* Replacing the thermal paste and pads;
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* Installing heatsinks on the back panel, to cool the GDDR6;
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* Removing the metal bracket and the I/O shield (they're only needed if the
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board is mounted in the rig);
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* Re-running the test suite mentioned above to see if I had won the silicon
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lottery a second time (luckily I did);
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* Modding the heatsink.
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The heatsink mod let me solve one of the problems I was having with the board:
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how do I get rid of 200W of heat? So far I had the portable AC, but I couldn't
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keep using a heat pump to cool a single board.
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When they're in the mining rig, the BC-250 all have their heatsinks laid out
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lengthwise, so a single array of fans is enough to cool all 12 boards at once.
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If you want to use one of these boards on its own, you need to get a bit more
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creative to get rid of the heat.
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The most common solution in the community is the [heatsink
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mod](https://reddit.com/r/BC250Gaming/comments/1rjc3io/), which consists of
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literally cutting open the heatsink in the section above the APU to make room
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for a fan.
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It's a somewhat long and tedious job, but it's not impossible to do. It's also a
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pretty repetitive task, so once you get the hang of it, it goes by farely
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quickly. In the end all it took was a pair of scissors, some good music, and an
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hour of my time.
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It's a bit *rough around the edges* (*literally*), but it works. And the hole is
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big exactly as a 120mm fan, so one of the two fans can blow directly onto the
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APU.
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---
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Since this article has gotten pretty long, I've decided to split it into
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multiple parts. In the next one, we'll design a custom case for my needs.
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