J-PAC Losing Sync with CRT_EmuDriver

[twistedsymphony]

I was in a discussion on MAME over on KLOV and had recommended CRT_EmuDriver w/J-PAC to someone. Another KLOV member had warned against it and had this to say:

...Andy said it has to do with the sync IC on the jpac not liking the software timings set by CRT emu driver. He said that a future version of the jpac would be more lenient on the timings but he's not able to develop the sync IC on the existing board any further and it's due for replacement as the sync IC is no longer manufactured.

...

Andy said it has to do with the sync IC on the jpac not liking the software timings set by CRT emu driver. He said that a future version of the jpac would be more lenient on the timings but he's not able to develop the sync IC on the existing board any further and it's due for replacement as the sync IC is no longer manufactured.

all of the relevant info is above but you can see the thread here: http://forums.arcade-museum.com/showpost.php?p=2905495&postcount=32

I only have 1 cab setup with CRT_EmuDriver and it honestly hasn't got much use.... I was wondering if anyone else has experienced this loss of sync problem and if so if there is any way to help keep it from happening.

[cools]

After buying one J-PAC donkeys years ago I never used another, the lack of a built in sound amp remains a ridiculous anomaly to me.

[Calamity]

I've experienced the same problem with the j-pac loosing sync, it can be really annoying. There are some threads in this forum mentioning the issue. The thing is none of the first 3 units I bought in 2007 had this problem. The ones I bought one or two years later do have the problem. I had always assumed it was related to the power supply. This is because in my experience the more devices I plug to the USB ports, the more often the j-pac looses sync. So usually it will loose sync when I plug my keyboard to do some setup job, but then stay perfectly synced when playing games. To get it back in sync you just need to unplug the usb and plug it in again. The problem with this is MAME won't recognize it again after the emulator's initialization so this can ruin an epic game. Due to the randomness of the problem, I have never been able to determine the cause with full certainty. If Andy says it's related to the video timings, I think we should trust him as he knows how it works internally. Fortunately the timings are fully customizable for both VMMaker or GroovyMAME, so if we found the root of the problem it wouldn't be difficult to avoid it.

[cools]

I wonder if using a PS2 port instead fixes it.

[twistedsymphony]

I've experienced the same problem with the j-pac loosing sync, it can be really annoying. There are some threads in this forum mentioning the issue. The thing is none of the first 3 units I bought in 2007 had this problem. The ones I bought one or two years later do have the problem. I had always assumed it was related to the power supply. This is because in my experience the more devices I plug to the USB ports, the more often the j-pac looses sync. So usually it will loose sync when I plug my keyboard to do some setup job, but then stay perfectly synced when playing games. To get it back in sync you just need to unplug the usb and plug it in again. The problem with this is MAME won't recognize it again after the emulator's initialization so this can ruin an epic game. Due to the randomness of the problem, I have never been able to determine the cause with full certainty. If Andy says it's related to the video timings, I think we should trust him as he knows how it works internally. Fortunately the timings are fully customizable for both VMMaker or GroovyMAME, so if we found the root of the problem it wouldn't be difficult to avoid it.

I'll keep an eye out if this ever gets triggered and what game/video mode was being used when it happens.

Though, based on what you've said it sounds like if the voltage drops in the J-PAC it has a higher probably of losing sync maybe powering it from a wall wart instead of USB would help ease/solve the issue? or as cools suggested using PS-2 instead of USB though I would think that'd be dependent on how your motherboard routes power... if it supplies power to PS2 on a separate rail from USB.

FWIW my cab is using PS-2 for J-PAC instead of USB and it's going to a Sanyo 20EZ monitor with an inverter board.

[Calamity]

I'd say in my board PS-2 and USB are not independent, regarding power. Plugging things to the PS-2 (e.g. a mouse) caused the same problem.

[twistedsymphony]

I wonder if you built a custom cable that splits out the power wires into a Molex connector instead of USB/PS-2, if that would help.

[Calamity]

I wonder if you built a custom cable that splits out the power wires into a Molex connector instead of USB/PS-2, if that would help.

I have close to zero skills for anything requiring wiring or soldering. So no, I haven't tested. I you want to be fully sure you should try feeding the j-pac with some power source that is totally independent from the pc.

[yatzr]

This is the first I've heard of this problem.  I've had 3 jpacs, 1 older one that had through-hole LEDs and two newer ones with surface mount LEDs.  I don't think I've ever experienced this.  I often plug in keyboards and usb thumbdrives while it's on too.

[Andypc]

I had this problem when using a j-pac with the usb cable. Switched to the ps/2 cable and the problem went away. Just need to make sure you get a motherboards with at least one ps/2 port. Now all I need to sort out is the strange vertical ghosting line I'm getting!

[twistedsymphony]

I wonder if you built a custom cable that splits out the power wires into a Molex connector instead of USB/PS-2, if that would help.

I have close to zero skills for anything requiring wiring or soldering. So no, I haven't tested. I you want to be fully sure you should try feeding the j-pac with some power source that is totally independent from the pc.

That's a good point. I'm very well versed in electronics and soldering so I might buy another cable to mod and try it out...  of course I haven't seen it drop the sync yet so I'll wait until it happens before I try anything to stop it.

Maybe I'll plug a scanner in or some other USB power hungry device to see if I can trigger it.

[Calamity]

Ok I knew I had read about this before, it was in the old Spanish forum. Check these posts (the whole thread indeed):

http://foromarciano.org/foro/thread/52/27/25227_6.html#post253912
http://foromarciano.org/foro/thread/52/27/25227_7.html#post254817

Basically these guys found that ensuring the voltage didn't drop from 4.99 volts the j-pac was stable.

[Calamity]

Maybe the fact I'm using a cheap Asrock board is the problem after all.

[adder]

dont know if this would help but worth a look anyway:
http://www.ebay.co.uk/itm/351069092683

[twistedsymphony]

Ok I knew I had read about this before, it was in the old Spanish forum. Check these posts (the whole thread indeed):

http://foromarciano.org/foro/thread/52/27/25227_6.html#post253912
http://foromarciano.org/foro/thread/52/27/25227_7.html#post254817

Basically these guys found that ensuring the voltage didn't drop from 4.99 volts the j-pac was stable.

nice find.

Thinking about this more I wonder if we put a big honkin capacitor on the 5V input on the J-PAC if it would help... this can help keep the power stable, a lot of car audio guys use big (1 Farad or 1/2 Farad) capacitors to help keep the voltage in their car stable with the huge draw of their speaker system... it keeps the lights from dimming everytime the bass hits. Something like this on a smaller scale could potentially work on the JPAC to filter out brief dips in power so long as the voltage doesn't dip below 4.99 for a sustained length of time it could be a cheap/universal fix.

dont know if this would help but worth a look anyway:
http://www.ebay.co.uk/itm/351069092683

Good thought but it would probably cause some issues with the PC getting data on 2 separate ports. If you were thinking of using one end to power from an external supply then it could potentially cause damage to the USB power line in the PC...  the simplest solution without using any tools would be to buy a powered USB hub and run the J-PAC from that.

[adder]

Good thought but it would probably cause some issues with the PC getting data on 2 separate ports.

i thought only one of those male usb connectors would have the 4 pins hooked up, and the other one would just have 2 pins (+5v and ground).
(if not you could just remove the two middle (data) pins from one of the male ends with eg. a very small flathead screwdriver)
ps. dont know how the jpac would feel about all this tho 

[twistedsymphony]

Good thought but it would probably cause some issues with the PC getting data on 2 separate ports.

i thought only one of those male usb connectors would have the 4 pins hooked up, and the other one would just have 2 pins (+5v and ground).
(if not you could just remove the two middle (data) pins from one of the male ends with eg. a very small flathead screwdriver)
ps. dont know how the jpac would feel about all this tho 

that's not a bad idea... it might actually work 

[Andypc]

If you can use a ps/2 cable it is much better. I have not lost sync once since switching cables and have had the cab on for 48 hours straight.  Also you get less lag with ps/2. Win win.

[Calamity]

If you can use a ps/2 cable it is much better. I have not lost sync once since switching cables and have had the cab on for 4 hours straight.  Also you get less lag with ps/2. Win win.

Andy has stated that ps/2 having less lag than usb is a myth, if not exactly the opposite.

[twistedsymphony]

yeah, I don't buy that PS/2 would be faster in any sense...

USB 2.0 (which is what the J-PAC uses) has a transfer rate of 480 Mbit/s while PS/2 is 62.5 kbps or 0.0625 Mbit/s that's an ENORMOUS gap in speed even with the larger overhead with USB based on being a less-direct method it has to maintain 2-way communication and would fall on it's face with any significant lag.

doing a little digging on the topic I found an interesting discussion on it here: http://www.overclock.net/t/1410493/ps-2-vs-usb-mice-input-lag

the consensus seems that even though PS/2 is more direct it pales in comparison to USB 2.0 in terms of both speed and latency.

[Andypc]

The consensus seems that even though PS/2 is more direct it pales in comparison to USB 2.0 in terms of both speed and latency.

More bandwidth doesn't necessarily mean less lag. The article you linked to actually say's ps/2 is faster than usb 2.0 for keyboards due to the access to the cpu and only slower for mouse due to polling. J-pac is works like keyboard input.

My point was your not going to notice any disadvantages from using a ps/2 cable and it's much more stable in terms of j-pac sync. Also your much less likely to be connecting or disconnecting ps/2 device's in normal use. Where as you may well be plugging in usb devices that may cause a slight change in the power supplied to the J-pac.

All I'm really trying to say is that I had this exact problem, I changed cables and the problem completely went away.

[adder]

anyone know if the sync issue generally happens with newer jpacs only, or does it affect the old ones also?

[blontic]

I have used CRT_EmuDriver and a JPAC in about 5 cabs now and never had this issue. Always used PS2 though. JPAC probably isn't needed with these drivers but it does help with the bios screen resolution, but ATOM-15 may solve that issue in the future (and save about $80 for the JPAC)

[twistedsymphony]

The consensus seems that even though PS/2 is more direct it pales in comparison to USB 2.0 in terms of both speed and latency.

More bandwidth doesn't necessarily mean less lag.

I get that...  which is why I mentioned the bit about 2-way traffic...  in order to maintain that speed AND be in sync the latency needs to be low or it wont work. I'm not advocating for one over the other, just trying to debunk that USB is somehow bad due to lag.

My point was your not going to notice any disadvantages from using a ps/2 cable and it's much more stable in terms of j-pac sync. Also your much less likely to be connecting or disconnecting ps/2 device's in normal use. Where as you may well be plugging in usb devices that may cause a slight change in the power supplied to the J-pac.

All I'm really trying to say is that I had this exact problem, I changed cables and the problem completely went away.

You're right that you're much more likely to hot-swap a USB device than a PS/2 device and that's great that switching to PS/2 worked for you, but that doesn't change the fact that using PS/2 instead of USB didn't help some other people in the thread. Maybe it will help some people, but it's not going to help everyone...

I'm not trying to start an argument, but using a PS/2 cable instead of USB doesn't seem to be the silver-bullet universal solution to this problem. It's worth investigating further.