The good old Z80... one of my favorite processors. If I am not mistaken, after the Z180 many more iterations of the Z80 (compatible) chips were available from Zilog. One of them even the equivalent of a 200Mhz (pipelined) Z80! Absolutely fantastic. I would be very, very interested in buying/building such a system (and/or with the Z180, and Z80). I'd be running CP/M on it (wonderfully efficient OS) and Unix. And it would have to have mountains of LEDs of course :-) Thank you for sharing these extremely interesting developments and possibilities with us. A joy to watch!

One thing I've learned in my exercise to try to get the internal serial ports working is that 20 Mhz was a poor oscillator choice. 18.432 Mhz would have been better, or even 11.0592 Mhz. 18.432 Mhz could be used at 1X on a 20 Mhz Z180, or at 2X attempt to overclock a 33 MHz Z180 to 36.8645 Mhz, and would be supported by RomWBW without modification.

Since Wayne's ROMWbW supports John Coffman's Mark IV Z180 ECB sized board, I'd bet that there are drivers for the onboard serial port there. It has been decades since I wrote code for one, but I seem to remember that its similar to the SIO.

A more efficient test for prime numbers is to run all the numbers from 2 to square root of the number being tested.

To my opinion, when having the right tools, soldering QFP and even QFN devices is really not that hard.

One step forward would be to just make a board with the Z180 with serial and some expansion slots. So a motherboard and daughterboard expansions, compliant to RC2014.

As always amazing work Scott. Can we expect to see this board on your blog and OSH park soon? I'd love to build one.

For soem reason I can't get XMODEM working when using the Z180 board. The SIO has its own crystal and it works fine when I use the Z80 build of RomWBW with my Z80 bnoard, but when I switch to the Z180 it stops working. Any ideas?

Well, I think is is the same to replace the old-school Z80 by an ARM Cortex with 180 Mhz. I use the very good SDCC Compiler for an own OS for my Z80. Asm is good but C is better... Prime numbers with Mersenne algo was also my first C program to test my Z80 :-) I loaded the board in my Eagle software (know this since 1993 V1.0 :-) and I wonder if the boards work withour a mass layer because some vendors have problems and produce short cuts.

you don't need special equipment to solder QFP. it's very easy to drag solder them

@smbakeryt ... I do not know if you have ever looked at the ez80 Acclaim processors or not but I notice one thing about it that I find most disturbing...... It has all the relevant signals of a normal z80 except one.... the very important M1 pin. How does Zilog make a nice chip like this and forget to include the M1 pin? IF you know anything about this, I'd appreciate any info you might be able to fill me in on. ....nice design BTW!

If you where to sell one of those boards premade, I'd snap one up.

At this rate I think it could be viable to sell these boards. Like I get it it's not that hard to order one board and so on but if you could just buy the board and components in one bag it would make it so much easier. I would buy one.

Excellent work and video! Have you thought of testing both at the same speed to see if the 180 is faster at processing than the z80?

You should have ran the test with both processors at the same speed . What I know is the z180 is a bit faster per mhz than the regular z80.

10 REM from www.robertsharp.co.uk/2010/10/08/prime-numbers/ if anyone wants to play at home. i'm about to run this on my Briel Altair 8800 micro, for the heck of it. IIRC the Briel emulates an 8080 at 2MHz, synced up my machine to your video after a few numbers went by, it's definitely slower than your 7MHz Z80 i added "STEP 2" to line 40 to speed things up a bit, i put "5E6" as the limit to see if it would break anything, i might have to wait 'til next week to find out ;)