@BreadPie thanks! I was hoping there was a more elegant solution, but I’ll try just spreading the saves around the other VMUs for the games that support that.

The Mac version of Redream doesn’t have shared VMUs, so hopefully a future update will sort the Retropie version in this regard.

https://pastebin.com/hDdGfrDm

Here it is, I hope this helps.

[edit]

Had a quick read through of the log myself after posting it. I noticed I didn't actually have a bios file to boot to. Bios file copied, problem solved.

Thanks @mitu

I downloaded the BIOS and the new hash file for MAME 0.223 and everything is working!

SOLVED

Oh, yeah, forgot it's using $md_inst for user data.

Hi man! I have the same problem. Did you solve that?

Today I managed to test all of the components outside the case, and everything works with my test Pi. Running off the battery without a booster works just fine with a Zero.

0_1505063029610_Photo Sep 10, 11 32 33 AM.jpg

Cranking up the volume in RetroArch makes the piezo loud enough to hear for general gaming, even if it's not quite high fidelity.

Everything plays really nicely now that I'm using the board where I soldered to the chip pads instead of the old "make your own test pad" method.

Next up I need to make everything fit in the actual case. First up, removing unnecessary stuff from a Pi Zero. This looks awful, but it works. If anyone has tips on removing the USB ports, HDMI port, or camera connector in a cleaner manner, please let me know.

0_1505063223272_Photo Sep 10, 12 53 15 PM.jpg

Every little bit of thinness is going to help with this build.

0_1505063257077_Photo Sep 10, 12 56 11 PM.jpg

seeed is on my (long) list of recommended PCB shops. DFRobot is another... for small orders they are mostly pretty competitive with each other, just depends what fab features you need as some extras are more expensive than others. for instance, OSHPark is definitely one of the more expensive places, but they include ENIG finish in that price, which pushes the price up massively at PCBWay. it's definitely all horses for courses and worth shopping around

I found "SoftVMS" and tried to run it in the emulator but it didn't work. Here is a link to the source code if it helps:
http://www.zophar.net/consoles/dreamcast/vms/softvms.html