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No. The five of us who are left are now responsible for all the work done by the original 17. We're maintaining products that have been passed from their original developer through three or four people on their way to landing in our laps. This, along with the various cloning attempts and one bizarre episode involving the Canon copier in the office, has rendered all of us unsane.
Anything that is unrelated to elephants is irrelephant Anonymous - The problem with quotes on the internet is that you can never tell if they're genuine Winston Churchill, 1944 - Never argue with a fool. Onlookers may not be able to tell the difference. Mark Twain
No, not on the road. On the address bus or data bus.
Bus collisions happen when outputs of two different chips output a different signal to the same line of the bus. It's a short circuit which can easily fry one or both outputs, ruining one or both chips involved.
The solution? Like on a busy intersection where two roads cross: A traffic light, plus some bus drivers which always cut off one side of the intersection while opening up the other at the same time. This way a 'red light' could not be ignored, even if it accidentally happened.
What I need that for? I'm building a single board computer to try some things out. It will get plenty of RAM (at least 1 Mb), a CDP1802 BCE processor at 5 MHz, traditional bit banged RS232 serial I/O and a MC6847 graphics chip with all the display memory it can handle and above mutual exclusion device to allow both the CPU and the MC6847 to access the display memory.
The sad thing is that the whole thing will be obsolete once it works, because my goal is to build a even better 'old computer' and wanted to have some things worked out before trying to tackle everything at once.
Unless... Would it not be great if the single board computer became the graphics card? The main processor would upload the graphics resources, maybe procedures and graphics commands to the processor and leave it to do all the work. That would be an extremely modern design with stone age parts, actually.
We need some kind of port for that, working title 'DGP (decelerated graphics port)'. It would not be very fancy, but we also don't need to transfer gigabytes of graphics data all the time. It's more like kilobytes, one millionth of the traffic to a modern graphics card.
So what would be your choice for the job?
1) I have two CDP1854 UARTs, which can be hooked up to the processors quite directly. The downside is that this serial connection will work at a bitrate around 28800 kilobits/sec max.
2) I also have two CDP1851 parallel ports. They are just as easily interfaced to the processors and may fall just short of the data rate we need.
3) Another shared RAM buffer, this time between the two CPUs. Nothing is faster than accessing memory directly. So far, so good. The downside here is that the memory, the busdrivers and the bus connector to the main processor's bus will eat up a lot of precious space on the circuit board.
So, which bitter cup would you drink out? Or do you have a better idea? Quick, I want to have great 3D graphics on a 8 bit computer!
I have lived with several Zen masters - all of them were cats.
His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.
Last Visit: 24-Sep-20 6:59 Last Update: 24-Sep-20 6:59