Corvus Concept

kevan(a)heydon.org wrote: Well, I am sitting here looking at a little book with title HARDWARE DESCRIPTION THE CORVUS CONCEPT You might think that with a title like that it would have connector pinouts, but, um, not quite. Well, it does have the pinout for the bus slots, which are like Apple ][ slots less DMA support. So what can I find about video? The display area is supposed to be 560 x 720 dots. The monitor used by Corvus was a Ball HD series monitor (so says the manual) in a Corvus-peculiar case (so says me). It looks like all the timing is derived from a 16.364 MHz clock that is generated on the memory board. That gets divided by the "horizontal counter" (74163s at U202 then U203 and U204) to produce a 34.669 KHz clock that is the horizontal scanning frequency. There is also a "vertical counter" (at U301) to produce a 50 Hz or 60 Hz vertical sync clock. "The video shift registers comprise 74S299 U106, U206 and 74ls299 U306..U806 for video data. The data is shifted at 16 MHz in two pairs of registers. The output of one register is fed directly into a 74S157 multiplexer U104 which is switched between two inputs at a 16 MHz rate. The other register feeds a 74S112 flipflop U103 which delays the data by 30 ms and then feeds it to the multiplexer. This makes a data rate of 32 MHz." I'm not much of a hardware guy, but I hope that gives you some clues for board-tracing and monitor selection. Note that the system can run the monitor in either landscape or portrait mode (hence the peculiar case, with slots for the base on two sides). I think you are supposed to tell it how you've got the monitor positioned with the VERT/HORIZ switch on the back. That doesn't change the video timing, it changes how the software draws into the memory. Now what about the keyboard? I gather there is a 6551 UART at U310 that receives keycodes, one for each key-down or key-up. Key-down codes have the most-significant-bit set; key-up codes have it clear but are otherwise identical to key-down codes. ... Some other notes. Jeff Kaneko wrote that the operating system was "Unix-like". I don't know, I haven't seen it run much less try to hack on it, but from reading the manuals I'd say it was more p-System like, except that it runs 68000 code instead of p-Machine code. The hard disk(s) could be hooked up over the Omninet (in which case the disk box was connected to an Omninet-attached disk server box) or via a hard-disk interface that sat in one of the Concept's expansion slots. There were also expansion cards to control 8" and 5.25" diskette drives. I'm not sure exactly how the VCR-backup stuff works. From reading another manual (the Disk Drive Installation Guide) it looks like there is an option for the disk to have a "Mirror" built-in. There are four DIP switches on the back that need to be set different ways for different circumstances: no Mirror built in => all closed Mirror built in, NTSC VCR => all open Mirror built in, PAL/SECAM VCR => 1 closed, 2-4 open ... Well, I hope that helps a bit. Yes, I have one of these. No, I haven't done anything with it as yet, save haul the CPU, monitor, and keyboard up to VCF for folks to gawk at. -Frank McConnell