I`m intrigued by the 68C50 idea, if the humble 1MHz 6850L will cope with a CPU running at 8+MHz, then it seems reasonable to assume that a faster UART could handle a higher CPU speed, maybe even 16.384MHz?
the problem Now of course is that everywhere I`v looked doesn`t have any.
So... any ideas where I could get one from (at a reasonable price)?

also, I had a look at the WDC chips I have and you`re quite right about the 14MHz thing, there are indeed marked up as such, so No idea where I got the 10MHz number from (unless it was from the guy on Twitter mentioning it), eitherway, if this 68C50 idea works, then 16+MHz isn`t too much of a push room temp or otherwise I should think.

currently I have a few projects on the go in the area of CPLD and also AT1284P chip defines/libraries, so work on NINA is on the back burner for a bit, but not Too long in case I forget where I was! (I keep lousy notes).

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Also on Twitter as "YT2095".

If you're interested in high speed 6502 computing, using an FPGA to implement the core, peripherals and some local memory can get you to 100 MHz.

WDC apparently does have their 65c51 available, although I don't see it in the distributors' online catalogs. You might have to order it direct from WDC. It's also in 14MHz. They did have a bug with even parity and I don't know if they ever got that taken care of. Who uses parity though?

The 6850 does not have its own onboard oscillator and baud rate generator IIRC. The 6551 can use an external oscillator if you want. It's not restricted to the interal one, or even the internal baud-rate generator.

I have used the 6551 at all standard baud rates from 50 to 19,200 (the slower rates being when I was experimenting with cheap modems for cassette tape 25 years ago), plus 31,250 for MIDI, using 500kHz generated by a 6522's PB7 output off T1 connected to the RC (pin 5) input, and never had any trouble with any of it. I know it can go to at least 125kpbs with external clock input on pin 5 for both transmit and receive. My 6551 hardware and software has always worked on first try except when I lacked the 22pF capacitor from pin 6 to ground in the crystal circuit.

The only thing I don't like about the 6551 is that a couple of the controls are merged into the same control bit, where it would be nice to control them separately.

Do use the CMOS version though (65c51) because the NMOS did have a quirk in that, IIRC, if its CTS\ goes false during the transmission of a byte, that byte does not get finished. Instead, it is lost. The CMOS version will finish the byte.

For any future designs I will probably just use the 14-pin-DIP SPI MAX3100 which has 8-byte transmit and receive buffers, and talk to it through a 6522 or Daryl's 65SPI. The MAX3100 is IrDA-ready, too.


That's what we're depending on you Verilog & VHDL gurus for! We need hobbyist-solderable IC or two, or tiny module, either pre-programmed or that automatically loads itself from a small serial EERPOM upon power-up, so we can take advantage without being HDL gurus ourselves or require it to be dependent on PCs and particular OSs or PC software.

My '816 Forth runs 2-3 times as fast as my '02 Forth at a given clock rate though, so a 20MHz '816 with readily available memory and I/O ICs would have the speed of a 50MHz '02, in Forth. If we can get to all 32-bit (data bus, all registers, including DB, PB, DP, so there are no bank or page boundaries), the performance for high-level languages would be a lot better at 20MHz than a 6502 would be at 100MHz, and do things relating to multitasking, multithreading, relocatable code, etc. that a 6502 couldn't do at any speed.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Maybe a 6502 drop in replacement board with a FPGA on it would be fun.
Thinking about FPGA, a small board with 3.3V regulator, 5V/3.3V level converters, and boot EEPROM would be fun, sorta replacement board for the XC95xx CPLD-s that i currently use. Maybe something that would fit in one of those big 64 pin dip sockets(like the MC68000). Such a board would be very interesting, since it would be fully compatible with our 6502 sbc-s.

Thinking about it... I want one!

FPGA drop in replacement boards have been discussed in this thread, but it never lead to anything concrete. If there's new interest, let's continue the discussion there, and not clutter this thread.

That's fair enough. I mean, Address bus , Data bus, glue logic (well, interfacing logic), simple I/0, CPU, RAM, ROM - any 8 bit machine built using '70s parts is going to look like the MUK101 if you think about it. Take a look at Grant's lovely Z80 schematic, very familiar indeed...