Later. We are doing the cartridge based on the original SFG schematics from Yamaha. The only difference is that all the logic (except the chip for 4MHz generator) and YM2148 chips are emulated by Altera. And the amplifier was "borrowed" from the Carnivore2 cartridge to save space. All the rest is the same.
Hello Alexey.
Here's a small contribution to your project. I hope it helps.
I did some debug checkings on the files you published, and found some issues that, if left unfixed, would have caused malfunctions. They are:
1) The pins 1 and 2 of AU1 (RC4558) have a incorrect connection with the GND.
2) The track from pins 6 and 7 of AU1 (RC4558) is shorted with +AV12.
3) The TCK pin of FPGA is short with the VCC5 line.
I appreciate your work and wish you good luck. :)
Alexey...
hmmmm... is another mistake? L2, L3 and L6 is shorted?
With ultra-rigid specifications Gold-plated DB25 connectors for only $154.95, the cable will
emphasizes the lovely sight between both boards.
HAHA oops I just googled that cable type, picked the best looking one, without looking at the price 
Anyway what I meant to say is that perhaps a round cable looks less messy/ugly than a flatcable 
Thanks, MSXPro for checking the board! That is the image of the board before the design review that we planned to do during the upcoming weekend. I will definitely pass your findings to our engineer so he could check for possible problems. And your input is very much appreciated.
Btw, did you check the 07 file or 06 still? I uploaded 07 only yesterday.
Hello Alexey. All check is from 07 file.
And here's the new board for the side slot. It replaces the Yamaha KYBT1/2 unused network module, but can be also used separately, with 50-to-60 pin adapter:
The board was routed manually as autorouter gave up on it, but I didn't... ;)
I'm in for one of these boards for the side slot. I have a YIS503/II which misses it 