I feel I've had my share of luck with the arcade lately, so I thought hey, why not push it a bit further? It's not over until the box is bricked and I'm all tears and regret. All of these tips require that you have root access on it already.
Boot faster!
The boot process is actually very fast, but the arcade has a few built-in splash screens, which not only takes time to play out, but is also followed by seconds of doing nothing - scripted delays. This happens in /etc/init.d/S99game
, and can be removed by adding the # symbol to comment out the lines. By disabling the following lines you will shave a solid 13 seconds off the boot time:
#./mplayer -af volume=-19 -softvol -softvol-max 100 arcade1up.avi #sleep 1 #cat /root/565/legal.565 > /dev/fb0 #sleep 5
..and the device now boots in less than 6 seconds - that's not too shabby!
Overclock it!
The Linux installation supports frequency scaling, and the current speed can be read with
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
If your arcade is like mine, it should output 1008000. As you can see it's currently set to 1GHz, but the CPU is capable of so much more. I used a stick-on heat sink to assist the cooling a little bit.

Heatsink installed
You can list the supported frequencies with the following command:
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
30000 48000 60000 72000 84000 96000 108000 120000 132000 144000
156000 168000 180000 192000 204000 216000 240000 264000 288000
300000 336000 360000 384000 408000 432000 480000 528000 576000
600000 648000 672000 696000 720000 744000 768000 816000 864000
912000 960000 1008000 1056000 1104000 1152000 1200000 1248000
1296000 1344000 1392000 1440000 1488000
..but that doesn't mean you can pick from the top shelf. I found that my arcade runs stable at 1.248 GHz. Any higher and it will crash immediately.
# echo 1248000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
Add this to one of the startup files if you want it permanently. For me, I'm still just playing around with it to see what it's capable of.
Low on disk space? Use a memory stick.
Some games are demanding in terms of disk space. If you added the USB port, you can use an USB stick for extra storage. You can mount it as
# mount /dev/uba1 /mnt/udisk
..provided that you have the same partition scheming as I do. You can symlink the games from /root/roms or reconfigure the roms directory in mame.ini.

Reassembled with USB hub and memory stick
As you can see, there's also no problem introducing a USB hub to the equation, in case you want the keyboard and the USB stick connected simultaneously.
BerryBerrySneaky here. I too have some analysis of the Arcade1Up boards. (I documented the USB mod you mentioned.) Here's what I've found so far:
https://www.reddit.com/r/Arcade1Up/comments/a02870
and/or
https://facebook.com/berryberrysneaky
Nice work! Very well explained. Thanks!