DigicoolThings Forum

... in person, from a store, in 2026.

Before I realized one of the local electronics parts companies has a partnership with Digikey I ordered several things for my MECB boards from a local shop called Akizuki Denki. Instead of getting them shipped in person I decided to pick them up in Akihabara so I could browse the junk stores and also to see if there was a used Google Pixel 8a phone for a side project.

The HAM radio and electronics parts scene in Akihabara has been dying since the 1990s so I was actually surprised to find that some of the old "radio-kan" buildings were still standing. These buildings used to be packed full of stores that sold all sorts of electronics, electronics parts, computers and video games. These days they are mostly just run by stubborn tenants who probably won't leave until the building falls down.

Since I was never much into electronics I had never explored this area much but I decided to see what was still around. Unfortunately most of the stalls are permanently closed and several are only open on the weekends, but I was able to find a store with some Z80s and 8085s. So I bought the Z80s and a Z80 DMA controller and Z80 I/O chip.





I have no idea what I'm going to use them for but all four chips total were about $30 USD and I figured I would support what is possible the last shop in Japan to stock and sell 8bit CPUs.

Here's a Google image search to give you an idea of the vibes.

tarix76 wrote: Fri Jan 23, 2026 3:36 pm ...These buildings used to be packed full of stores that sold all sorts of electronics, electronics parts, computers and video games...

Wow. That area would be fun to explore!

I’ve been contemplating (backward & forward), with ideas on how I want to design a Z80 based MECB card.

I had originally been heading down the path of a HD64180 (PLCC68 package) based card.

But, more recently, I am now thinking that I should just start with a simple original DIP40 packaged Z80 based CPU card, and then add a Z80 family I/O card.

Later on, maybe move to the HD64180 for a subsequent PLCC based Z80 CPU card solution?

So, grabbing some Z80 components is probably a good idea. I’ve got a few in my parts drawers as well.

I'm not overly familiar with Z80/Intel processor interfacing but just had my first attempt at making an 8088 board for MECB and it turns out that the Motorola I/O card so far appears to work fine with it Though, admittedly, I haven't really put it through its paces yet and have only tested with a "Hello, World!" program. A Z80 and possibly an 8085 board (I will probably avoid the 8080 just because of the silly voltages needed for it) are still needed for me to complete the most commonly available 8-bit bus computers (... and there is also the 1802 and SC/MP but they are getting really hard to find).

epaell wrote: Sat Jan 24, 2026 1:15 am I'm not overly familiar with Z80/Intel processor interfacing but just had my first attempt at making an 8088 board for MECB and it turns out that the Motorola I/O card so far appears to work fine with it ...

Good to know!

You’ll note that the ECB bus signals are primarily designed around the Z80 / Intel requirements, rather than Motorola.
i.e. The seperate Read and Write control lines, and the seperate IORQ / MREQ address space etc.

Hence why my 6809 and 6502 CPU cards use I/O Bank select circuitry, to mimic the Intel bus (by allocating a memory back to I/O space).

I suspect the main issue with using the existing Motorola I/O card (with a Z80), will be in terms of interrupt handling limitations.

I was just thinking (in reference to a Z80 family I/O card), that I’d probably like to have a play around with some original Z80 peripheral IC’s.

epaell wrote: Sat Jan 24, 2026 1:15 am ... and there is also the 1802 and SC/MP but they are getting really hard to find.

And… Don’t forget the Signetics 2650

Yes, I noted the signalling likeness to those used by Zilog/Intel. I've yet to test the interrupt side of things (as with the 68008 board I didn't quite have it fully planned out and I neglected to add the pull-up resistors and apparently also pull-up resistors on the data bus to force the interrupt to vector $FF ... I'll try bodge those in and if it works prepare a v1.0 board, apart from that and inverting the signals I "think" it should work).

Oh, I wasn't aware of the Signetics 2650 ... OK, that gets added to the wish list as well

epaell wrote: Sat Jan 24, 2026 2:11 am Oh, I wasn't aware of the Signetics 2650 ... OK, that gets added to the wish list as well

LOL. Yes, the 2650 was (nearly), the first microprocessor based project I was going to build. Specifically, the "baby" 2650 / Pipbug based project published in Electronics Australia 1977.

But, just before I went down this path, the DREAM 6800 project was published, and the general design of the 6800 CPU (at the time), took over my interest as the way to go.

Of course, I currently have no idea where I would get an (affordable) 2650 chip to play with. I think they're pretty rare now.

BTW, I just added the missing pull-up resistors and tested the interrupt handling - it seems to work fine with the 8088 and 6850 ACIA (I set it up to generate an interrupt whenever the ACIA receive buffer has a character and the interrupt handler dumps all the registers to the terminal). I've also manually triggered the NMI and it too seems to work fine.