I have some more results. My 74HC4046 PLL worked pretty well to generate a fine tune clock rate. It is a bit jittery, so not ideal. As a result this data is probably worse than it really is.
These results are using hardware with 1) 150nsec EPROM ROM 2) 100 nsec SRAM 3) M2 upgraded buffer Processor stable speed speed at which LCD suffers Max no LCD speed Tundra 8MHz 6.25 MHz 6.45 MHz (missing pixels) 7.1 MHz NSC800 4MHz 5.71 MHz 5.81 MHz (bad chars) 6.62 MHz NSC800 3MHz pretty much the same as the 4MHz part Some observations 1) short opcode read cycle impairs NSC800; it can never be as fast on clock speed as 80c85. 2) as some speed, the LCD can't keep up so you get missing pixels 3) going faster than that doesn't allow the LCD to keep up, so it can't report status. Laptop hangs. 4) NSC800 seems to garble screen comms as opposed to corrupt the pixels. Indicates a memory access problem? 5) With both processors, you can stop accessing the LCD and go faster. Personally, I think I am just going to go for 2x speed increase and call it there. To do so, I think you must have * upgraded main ROM speed (150nsec) * upgraded system RAM speed (150nsec or faster?) (REXCPM?) * @5MHZ, any 80C85 and any NSC800 can work * Probably not a bad idea to piggy back the M2 buffer with a 74HC245. So, that's that, experiment over. I have a PCB design for NSC800 and on it's way for testing. I have a PCB design for 80C85, but I have not sent out for it. If anyone is interested in trying this out, let me know. Steve On Thu, Nov 12, 2020 at 12:35 PM Stephen Adolph <[email protected]> wrote: > keeping my experiment rolling ;) > > I just received the "high speed rated" NSC800, supporting 4MHz. > Now, I did successfully run the 2.5 MHz rated part at 5MHz, so I will be > interested to see if the 4MHz part is really any faster in the M100. > > as usual, I will report back. > > >>
