I recently switched the hardware within my arcade machine from a x86 PC to a Raspberry Pi 3. The reason for this was that I was getting fed up with the maintenance required for a Windows PC.
I’m pleased that I did, as I can now just download a new pre-configured Raspberry Pi image and I’m pretty much done! The only issue I had was getting the IPAC interface to work. It kinda worked but struggled with mapping some of the buttons and most of the player 2 controls. I believe the reason for this was that the IPAC emulates the keyboard and RetroPi has really been designed for USB joysticks.
So my solution was to pick up some of the cheap chinese USB joystick interfaces, at under £5 shipped with wires. At that price, I was not very hopeful. Well ... how wrong was I, they worked great. No delay and super easy to set-up. In fact I have ordered another one as I have a box of joysticks and buttons from previous projects that I would like to make use of.
You can pick one up from ebay here