After looking at the pictures above, doing some research on scan converters and scratching my head, here's my best guess on what this is. Please note that I may be wrong, but given Ode's reluctance to provide additional information, I'll have to trust my instincts.
As I mentioned in the other thread, this thing will allow you to connect your PC through Parallel, Serial and Audio ports to your JAMMA rig. However, here are the caveats:
1. Since it connects to the parallel port, you will need to use a TSR/driver (SNESKEY/PSXPAD) to convert parallel input to keypresses. Configuring the drivers may require some extra work. Conclusion: no advantages over the plug-and-play functionality of JPAC.
2. I originally assumed that this device would include a scan converter, but given the complexity of converting a 31khz VGA signal into 15khz (and that ShagMame only has 6 chips, none of which is VLSI) I have strong doubts that this thing will include scan converting circuitry. Therefore, I have to assume that this connects your VGA directly to the RGB monitor, which spells disaster if you don't change the scan frequency from 31khz to 15khz *through the video card*. Therefore, you will have to reprogram your card to output 15khz using MONARC, ArcadeOS, AdvanceMame, etc. and the ATI / Blade 3D cards.
Conclusion: not even close to the functionality provided by ArcadeVGA nor a good scan converter (i.e. Extron Emotia).
Based on the assumptions above, here's a comparison table between the two devices. (Please note that I'm not including the ArcadeVGA into the comparison, as I believe the ShagMame is closer to the JPAC than to the JPAC+ArcadeVGA combo).
Feature .........................................JPAC................ShagMame
Jama fingerboard............................yes.....................yes
Input to PC through................keyboard port........paralel port
Requires port drivers.......................no......................yes
Requires video drivers....................yes......................yes
Protects Arcade Monitor..................yes.......................no
Requires software config(1).............no.......................yes
PC audio port connection.................no.......................yes
Can use in Windows.......................yes.......................yes(2)
Notes:
(1) Besides the configuration required to drive an arcade monitor.
(2) With appropriate parallel port driver: SNESKEY for DOS/Win9X, PSXPAD for XP/2000
Final conclusion: A Jpac provides better functionality, more flexibility and true plug and play requiring no drivers for the controls. Regarding video, they are equivalent, just acting as a VGA passthrough. However, the JPAC provides safety so that you won't burn your arcade monitor if you accidentally send 31khz through the VGA port. Unless you absolutely have to use the parallel port, JPAC is the way to go.
Final disclaimer: these are just my assumptions and opinions based on them. If ode wants to challenge them, I'll be glad to hear from him; I'd love to be wrong, as this would be a killer product. However, there's a reason why nobody has done it yet.
-- Android
P.S. - Edited 6/18 to include lokki's corrections regarding video drivers