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I thought part of retro experience is searching for hard-to-find parts and figure out a way to test and use them. Z80 is truly retro now.

New parts are obviously the safest approach but working with used, often obsoleted parts is part of the retro ethos. More often than not, it is a mixture of old and new parts.

There are couple glueless Z80 SBC that are easy to build and parts are available from China. I understand the parts are used, but they seem reliable and definitely cheap. https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:simple80...

When I was a kid growing up in Taiwan, contract assemblies were common. Soldering was done with a pot of lead over charcoal fire. Kids populated the boards, adults dipped it in the pot of molten solder. We stripped wires with our teeth and made Christmas light strings. Kids were happy with...

These recycled parts need to be relabeled to release the original manufacturers of liabilities.

Pactec cm5 clam-shell enclosure is perfect for 100mmX100mm pc board. It is $10 new from Mouser, but surplus lots are sometimes available on eBay for $2-3 each in larger quantity. I’ve designed multi-board Z80/6502 computers for Pactec cm5-200 enclosure.

Alternatively, not having 3-d printer or sheet metal tools, I design to fit existing enclosures. Considering how cheap pc boards are, it is a reasonable approach. Bill

If your electric motor won’t start, most of the time is due to starter capacitor burnt out. It is so common that starter capacitor for many motors are easily accessible for replacement. I have to replace starter cap on my air conditioner a few years ago and heater fan motor last winter. Both...

I was still working when I heard of the hoard, so that must’ve been 15 years ago. How time flies! I’m not at all familiar with Retro Computer Club in Albuquerque. Tell me more. I’ll google it, right now.

Wow, nice! Albuquerque is home of Altair, did you managed to save a few? I remembered one time I was told there were a big surplus of Altair at Surplus City. By the time I got there, the entire crate was sold to a local collector. I missed out by a day or two. Bill

Some of my vintage computer designs can use either 44-pin CF adapter or DOM interchangeably without software changes. Physically DOM pin assignments are mirrored from CF, so I either plug in from the top or from the bottom to compensate for the mirrored pinout. From software driver point of...

I can not read the oscillator value. Is it 18.432mhz? The Z180 you are using is rated to 33Mhz and good for 36.8Mhz, so you can double the clock, but the rest of memory and logic probably won’t keep up. RomWBW auto detect the serial baud, but that needs a RTC, so without RTC, it defaults to...

hperaza has published a buglist for Z280 on retrobrewcomputers.org forum here, https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=742&start=0& It is mostly software bugs. I know of one hardware bug dealing with metastable problem with CPU and UART clocks. The fix is to use one clock...

Looking good. CPLD should have enough logic to do DRAM controller, CF interface, and I2C/SPI etc. This is my version of Z280 operating in ZBUS mode, Z280RC. It is ROMless and bootstraps from CF disk. It is 2-layer pc board, but if I were to design it today, I'll go 4 layer because DRAM is...

The 16-bit I/O space is useful to me in two designs: 1. 4K video memory and fonts are mapped to 4K of I/O so they are directly read/write accessible. 2. Multiprocessor communication over dual port RAM where main processor access its side of 4K dual port RAM as 4K of I/O, thus allowing up to 16...

Z280 has cache that is turned on by default, so it needs to be turned off to run self modifying code. Bill

I wonder whether you'll consider this as self-modifying program when a program creates another program in memory then executes the resulting program? This is commonly done in bootstrapping when a small bootstrap loads & executes application program from mass storage or when a loader program...

I try not to do self modifying code unless I absolutely have to. My most recent example is generating 800Khz pulse code modulation with Z80 to drive WS2812 (Neopixel) display. I imagine there might be self modifying CP/M BIOS code dealing with the floppy disk. Bill

It is actually quite a bit easier than you might think. WinCUPL has a TABLE keyword for lookup table and ROM that generates the logic equations automatically. I imagine it is just eight Karnaugh map generators with 6 addresses as inputs and data bit as truth table; one Karnaugh map per data...

The GAL is 22V10 which has 10 outputs. 8 of the outputs are ROM data output. Depending on the data patterns, 22V10 can hold 40-50 bytes of instructions, maybe more. The ROM is a bit-bang serial bootstrap loader at 115200N82. Z80 needs 36 bytes of instruction, but 6502 needs 47 bytes because...