PJ5 TTL CPU – Blog about the TTL based CPU design we're making

We’ve managed to do some more work on the display and I’m really happy to say we’ve got two bits of code running on it, the game of life and the Mandelbrot generator. We do have a problem with the display, currently sending data faster than 500KHz causes random junk to appear, we also get corrupt memory, we think some of this is due to the long ribbon cable (~500mm in length) so we need to do more investigation on this. So we’ve been using the speed switching capability of the CPU so that the calculations can be done at 2MIPS and then switch to the slower 500KIPS for writing to the display. The calculations are being done at 2MIPS to decrease the corruption in RAM, at 4MIPS with the display attached a lot of corruption happens, even at 2MIPS you can still see some. I’ve also built a second set of main boards and tested them, so we should soon be able to have two of these CPUs, one at my house and one at Jons. We need to rework the bus board, the clock and the code memory boards which s

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• Dharmik Parmar