Friday, July 25, 2014
Star Rider + DEXTER (25 July 2014)
I've got DEXTER rev3 stable enough that I had a chance to try it out with Star Rider. In short, the VBI frame number injection wasn't working at all and it's because of defects in the DEXTER firmware and software. I look forward to fixing these so that I can see if any kind of frame number detection is working.
Also, seeks seem to be getting ignored by the firmware which is odd. There may be a problem with the video squelch and/or the stand-by line. Again, this appears to be a firmware defect.
As you can see, laserdisc video is working but looks pretty bad. I'm not sure if this is just how Star Rider looks (like crap) due to being filtered through crappy ADC/DAC hardware on the expander board or if there's something wrong with the hardware.
And for those still reading (hehe), I did modify two of the ROM ICs so that the game will boot faster and get into the frame seek tests without having all of the inputs hooked up. I modified U52 (on the CPU board) so that the long color tests that start when the game is powered on are completely skipped, and the first ROM test is also skipped. Only the rug pattern tests remains because it goes fast. I happened to have an EEPROM that is pin-compatible with the 2764 used on the original and it seems to be working great. This thing is super easy to reprogram over and over again. I also modified U26 which is a 27128. Unfortunately, I do not have a compatible EEPROM for this one so I ended up reading it (it matches the U26 that is floating around on the internet), erasing it with a UV light, and re-writing it with a modified version of the self-test that immediately skips to the "search to" portion of the DISC TEST. The two former tests (RESET RESPONSE and WALKING BIT test) only test I/O from the main CPU to the PIF board, and don't actually test laserdisc I/O so I am not particularly interested in those for DEXTER development.