#+TITLE: PC Engines APU Comparison
#+DATE: 2020-06-16T23:43:02-04:00
#+DRAFT: true
#+DESCRIPTION: Comparison between PC Engines APU machines
#+TAGS[]: hardware pcengines
#+KEYWORDS[]: hardware pcengines
#+SLUG:
#+SUMMARY:

I've been looking at the PC Engines APU line for a while. They're a
line of medium size single board PCs with a DB9 serial connector and
no VGA port. They also have gigabit Ethernet and are often used as
firewall machines.

I want to get one and use it as either the home router, or an
experimental server to mess around with. Quite a few OpenBSD folks use
them and recommend them as OpenBSD router and server hardware. They
aren't too expensive, have decent specs and a small physical
footprint.

One thing that's always confused me was the naming scheme, which is a
little confusing at first. Initially there was the APU, then the APU2,
as described on their site, which makes sense. Then the APU model
numbers get a little confusing. They come in several variants, I'll
list them here for context.

#+CAPTION: Taken from the PC Engines website
#+BEGIN_QUOTE
 apu2d0 (2 GB DRAM, 2 i211AT NICs)
 apu2e2 (2 GB DRAM, 3 i211AT NICs)
 apu2e4 (4 GB DRAM, 3 i210AT NICs)
 apu3c2 (2 GB DRAM, 3 i211AT NICs, optimized for 3G/LTE modems)
 apu3c4 (4 GB DRAM, 3 i211AT NICs, optimized for 3G/LTE modems)
 apu4d2 (2 GB DRAM, 4 i211AT NICs)
 apu4d4 (4 GB DRAM, 4 i211AT NICs)
 #+END_QUOTE

What do the letters between the numbers mean? What is the significance
of the numbers in the first place?

Let's take the example =apu3c2=. The 3 here means it's version 3 of
the APU board. The APU 1 is no longer sold, so it's left out of the
list on the PC Engines website, along with most of their
re-sellers. The letter between the numbers is the revision of that
board. It's pretty much irrelevant for comparison, other than you want
to get the most recent one, as listed on the PC Engines website. The
revisions are mostly minor tweaks to the board. The final number is
the number of gigabytes of RAM (in most cases).

The APU2 boards have a single mSATA slot, and a regular SATA
connector, two mPCIe slots, and a SIM tray. Using the SIM tray will
remove the ability to use one of the two mPCIe slots. It comes with 2
external USB 3.0 type A ports, 2 internal USB 2.0 ports (header only),
an SD card slot, and a GPIO header. It also has 3 Intel i211AT gigabit
NICs, with the exception of the APU2D0, as mentioned below.

So what are the major differences between version numbers? They all
use the same CPU, the quad core AMD Embedded G series GX-412TC running
at 1 GHz. Everything else about the boards are practically identical
too. I'll give a description of the differences relative to the APU2
board.

The APU2D0 is the same as the regular APU2, but without a GPIO header,
and it has only 2 NICs.

The APU3 has an extra SIM tray, and the first slot, which on the APU2
is mSATA only can be used as either an mSATA or mPCIe slot. If you
were to choose to use both SIM trays, you would lose the ability to
use both the first mSATA/mPCIe slot and second mPCIe slot, meaning you
would be unable to use an mSATA drive. It also lets you do GPIO tray
swapping and failover. Other than that everything else appears to be
the same.

The APU4D2 has 4 NICs instead of 3, like the APU2. It also has three
mPCIe slots, with the first one being a dual mPCIe/mSATA slot, like
with the APU3. It only has one SIM slot, same as the APU2.

The APU4D4 is the same as the APU4D2, except it has dual SIM trays.

A lot of this information wasn't really obvious to me upon first
reading the PC Engines website, as there's no direct comparison
between the board, and the site relies on you flipping between
pages to find the details. The re-seller website I looked at also
didn't elaborate on the differences.

Here's a small table describing the differences.

| Board  | RAM  | Slot 1          | Slot 2    | Slot 3 | Ethernet Controllers | SIM Slots | USB 2.0 Connections | GPIO Headers |
|--------+------+-----------------+-----------+--------+----------------------+-----------+---------------------+--------------|
| apu2d0 | 2 GB | mSATA           | mPCIe/SIM | mPCIe  | 2 i211AT             |         1 |                   2 | No           |
| apu2e2 | 2 GB | mSATA           | mPCIe/SIM | mPCIe  | 3 i211AT             |         1 |                   2 | Yes          |
| apu2e4 | 4 GB | mSATA           | mPCIe/SIM | mPCIe  | 3 i210AT             |         1 |                   2 | Yes          |
| apu3c2 | 2 GB | mSATA/LTE Modem | LTE Modem | mPCIe  | 3 i211AT             |         2 |                   4 | Yes          |
| apu3c4 | 4 GB | mSATA/LTE Modem | LTE Modem | mPCIe  | 3 i211AT             |         2 |                   4 | Yes          |
| apu4d2 | 2 GB | mSATA           | LTE Modem | mPCIe  | 4 i211AT             |         1 |                   2 | Yes          |
| apu4d4 | 4 GB | mSATA/LTE Modem | LTE Modem | mPCIe  | 4 i211AT             |         2 |                   2 | Yes          |