Trash80toHP_Mini
NIGHT STALKER
The latter, a VidCard has nothing at all to do with memory on the logic board. CPU loads the frame buffer on the expansion card and then the card mooshes it around and shoots it down the cable.You mean, interfacing with the VRAM built into the motherboard (or whatever)? I doubt Nubus/PDS has enough bandwidth to pull the contents of VRAM at any usable frame rate. A FPGA board providing its own frame buffer to the system and outputting the video signal independently is definitely the way to go.
I figured it would have gone by the wayside by now.Unfortunately, it looks like the miniSpartan6+ FPGA board used in the VA2000 project is no longer sold which is too bad because, from what I've gathered, it was particularly well suited for this type of application (and relatively cheap).
Really, just forget about NuBus and design for PDS if you're going to get anywhere, listen to Gorgonops. :approve: Moving a working PDS card design onto NuBus is really no big deal by comparison to overall development.There are some boards (DE10-Nano, Zynq-7010/7020) that appear to be suitable (HDMI port, enough digital I/O pins, enough RAM, NVM to hold ROM) but these provide ARM cores that, from what I've gathered, share the memory on these devices and are therefore not suitable for low latency applications. Some projects (MiSTer for the DE10-Nano https://github.com/MiSTer-devel/Hardware_MiSTer) have gotten around that limitation by attaching memory to the I/O pins. My recollection from skimming through documentation is that 56 pins are required in Apple's Nubus, which rules out the DE10-Nano, for example, because half of the 80 I/O pins available on that board would be used by the SDRAM daughter board. I haven't looked more closely at the Zynq-7010/7020 but I suspect it has the same problem.
For PDS you shouldn't need all that many DIO pins as I understand it. @trag16-bit video would require sixteen data lines and four address lines plus PDS control signals, no? I'm guessing 24-bit would entail eight additional data and one address bit? From what I recall of the Amiga project, you don't even need all the 68030 control signals?
XGA _______ 1024 x 768 = 786,432 pixelsI agree. I think 1080p is probably the upper limit and there are still likely to be some issues, as you've pointed out.
WSVGA ____ 1024 x 600 = 614,400 pixels
720p _______1280 x 720 = 921,600 pixels which is less than
Mac 21" ___ 1152 x 870 = 1,002,240 pixels
1080p ____ 1920 x 1080 = 1,393,200 pixels, only a 39% increase over Mac 21" and far less than the 2 million plus pixels my IIfx drives adequately on its pair of NuBus cards.
I see no problem with 1080p, those cards have only 3MB VRAM each, but they are QuickDraw accelerated.
The NuBus Video Card documented in that book appears to be the original TOBY card for the Macintosh II. You've got the Sample Video Card firmware listings in Appendix B and Appendix C is the sample driver. Look at the information from the point of view of the 68030, not the NuBus setup in between, that makes it a sample PDS Video card spec, firmware and driver for the purpose at the start of this adventure. Build up from that foundation to the pinnacle of 1080p HDMI output from a 68030 PDS Mac*** displayed on a dirt cheap, lowest common denominator panel.That's encouraging. I skimmed through the video card specific sections of the Nubus documentation the other night, and came largely to the same conclusion. I would be thrilled to have unaccelerated video; I think that would be a major accomplishment. Accelerated video can come later
Page citation would be appreciated here, I don't see a problem so far.I'll look into it. One concern I have is whether a PDS graphics card can be used early enough in the boot process? There's a length discussion about that in the Nubus documentation for video cards.
*** That sounds like the definition of the Amiga project you linked, but for the obstacle presented by ZORRO III multiplexing.