What do you guys think? I'm not aware of anything like this that's already out there. It could then rebroadcast this at a different resolution, for direct connection to an external monitor, or transfer the data over USB to a modern computer for display or recording.Īn advantage of this second approach is that with appropriate software, it should theoretically be possible to make the external monitor into a second monitor, instead of a mirror of the first monitor. Once again, an FPGA or CPLD or fast microcontroller could watch the bus, and maintain an internal private copy of whatever's written to the frame buffer.
It might also need a way to detect the vsync signal, so it can know when to capture the frame buffer, to prevent tearing. Or with an SE or SE/30, the PDS slot might have everything needed. Physically attaching this to the Mac might be a challenge, but most of the necessary bus signals are present at the ROM sockets. On the compact Mac, the frame buffer is just a region of normal RAM at a specific address. The operation would be similar to NTSC-to-PAL converters or other scan rate converters.Īnother approach suggested by bbraun is to sniff the CPU bus, and watch for writes to the frame buffer area of RAM. An FPGA or CPLD or very fast microcontroller would be needed to buffer an entire video frame (about 20K of data), and then "rebroadcast" it with different video timings and some letter-boxing or pillar-boxing to make it fit an existing video standard like SVGA. The difficulty with this approach is that the Mac's native resolution and horizontal refresh rate aren't a close match to any existing video standard. It might be possible to rig some kind of pass-through connector for the motherboard connector to tap those lines, or extra wires could be soldered directly to the connector. That already has a 1-bit monochrome video signal, as well as sync signals, broken out on separate wires. One is to capture the video signal that's on the logic-to-analog board connector. And combined with bbraun's keyboard and mouse emulation, it might even provide for a compact Mac KVM, or remote desktop session. For a machine where the video circuitry or CRT are broken but the logic board is good, this could be a way to get it working. Or to do screen captures or video captures of old software running on the Mac. I'm not sure this has much real practical value, but it would be interesting to see a Mac Plus running on a large 24" monitor, or on a projection screen.
It would mirror whatever appears on the internal CRT. I think it would be cool to build some kind of video out adapter for compact Macs, either for direct connection to a modern SVGA monitor, or as some kind of frame grabber.
0 kommentar(er)
