Hey Level1, long time lurker, first time poster. I wanted to share a build that
has been very useful for me and maybe for others who need to get GPU-driven computing done on the cheap.
The build
RAM: Crucial Pro DDR5 2x64GB 5600 MT/s - 320$
CPU: Ryzen 8700G - 260$
Board: Gigabyte B650M Aorus Elite AX - 180$
PSU: SilverStone SST-EX-500-B SFX Bronze 80+ - 90$
Cooler: Thermalright AK90 - 20$
Total: 870$ USD
Current prices in your area may vary of course, these prices are what I payed a few months ago.
Wait, what about…
Disk: older 512 GB M.2 NVMe from the parts bin
Case: “open air test bench”, for now
Part 1: Introduction
This is a build I put together for assorted heavy workloads including
compiling, geo, video editing etc. Some ML stuff like computer vision, OCR,
transcription and… yeah LLM too I guess. I have experienced that LLMs can be
useful helpers in certain tasks, but I feel as of 2025 they are way way way
overblown and the LLM data center building fever and associated oligarch wet
dreams and their gleeful sycophants in my eyes is obscene.
Being a computer person whose earnings are fairly average in a country with low
median income of less than 4000$, I have been getting by with used Thinkpads
for the past decade. It is really amazing what you can do with these old
machines to make them like new, we keep them going for more than a decade doing
all sorts of useful things for people. After looking like they were going the
way of apple-like disposables, I am happy to see that there are new Thinkpads
with SODIMM instead of soldered RAM, but I digress.
So two years ago I decided I wanted to invest in a more powerful PC for some
work that the Thinkpad could not do or could do only slowly. I got a chance to
use a Beelink minipc with a Ryzen 5000 series APU for a few weeks and I was
quite impressed, however I did not particularly like that one can’t add a PCIe
GPU card later, also the decreased repairability and the complete lack of
professionalism on behalf of Beelink with regards to firmware updates.
Those minipcs with soldered RAM are particularly egregious with regards to
repairability, as any breakage suffered by the board will take down with it the
precious RAM and CPU. Oh the video output port broke? Wonderful, the RAM and CPU
are useless now too. Those with SODIMM are definitely more appealing to me as
at least the RAM can be salvaged, but a standard socketed (m)ATX/ITX setup yields
maximum repairability and reusability.
So I saved and waited for something nice to come along, and when the Ryzen 8000
Pheonix 1 series APUs were released on the AM5 platform in early 2024 with
those nice, big RDNA3 iGPUs which can use arbitrary amounts of main memory, I
thought “this is it”. Between the two options of 8600G and 8700G, the 8700G has
2 more CPU cores, and a GPU with 12 cores versus 8 in the 8600G. However the
Phoenix iGPUs are significantly memory bandwidth limited anyway so in practice
we see that the 8600G is only 20% slower than the 8700G for most workloads. The
8600G looked like a better value when purchased at around 180$, versus the
8700G which was generally around 300$ in 2024.
Exciting the possibility of 128 GB RAM, which meant 4 DIMMs, but later I read
here on L1 that 4 DIMMs is at present “complicated” with DDR5 and probably
slow. 64 GB would be too little when my nearly decade old laptop has 40 GB and
it is frequently maxed out for routine work, without local LLMs in the mix.
Later when 96 GB kits became available, it seemed like a small improvement for
a big price jump. But then there were rumors of 32 Gbit DRAM coming which would
allow for 64 GB on each DIMM! So I waited some more.
So a few months ago the 2x64 GB Crucial DDR5 kit was released and with shipping
to my country at a reasonable price of 320$. Ordered. Oh but the 8600G was not
available, and the 8700G had dropped to 260$, so 8700G it is.
I wanted a board for a compact case, but also the possibility to maybe someday
expand to 256 GB with somewhat reduced frequencies. A 2 DIMM ITX board is
therefore excluded. A full ATX board seems bulky and kind of pointless with the
lack of PCIe lanes on AM5; an x8 + x8 + x4 (electrical) board would make sense
but these are only available at a very high price such as ASUS ProArt X870E.
The 8000 Phoenix 1 series has a paltry 16 usable PCIe lanes, so a big board
with lots of PCIe capacity would be wasted anyway. Micro ATX with 4 DIMMS it
is.
The Gigabyte B650M seemed like a good value with a decent VRM, ample IO and a
sensible x16 + x4 PCIe layout, although with 8000 Phoenix 1 series we must
accept running the x16 slot at x8.
I did not like the surprise when the “8 layer” board I ordered later arrived
missing 2 PCB layers; the delivered 1.3 revision has only 6 layers! A sneaky
bait and switch by Gigabyte. The lesson learned is to always check if there
are multiple revisions of a board, as manufacturers frequently change wireless
and ethernet adapters between revisions, and even the entire PCB design,
lopping off 2 layers as if it makes no difference.
Physics tells us that it is easier to maintain signal integrity when more
layers can be used for routing dense PCB traces, which is particularly relevant
for high RAM frequencies. Well, as we will see, a good RAM overclock was
achieved in spite of missing PCB layers, so there is no need to further bemoan
Gigabyte’s treachery.
Next up, Part 2: assembly, software, tuning and photos. Lots of tricks to
improve Phoenix 1 iGPU (gfx1103) compute performance.
Part 3: Benchmarks. Lots of llamabenching.
copyright computeforpeople 2025
I give permission for this content to be incorporated in a machine
learning corpus or used to train machine learning models only when the full
corpus is made available publicly under an open content license and all code
used to generate said models is made available publicly under a license
compliant with the Free Software Definition.
