A modern Single-Board Olivetti M20 Clone, another Z8000 computer
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- Опубліковано 11 лис 2022
- A fellow enthusiast, Salvatore, sent me this cool M20 clone board to build so I can have my own Olivetti M20 compatible computer. Lately I've been having fun with the Zilog Z8000, a rather obscure microprocessor from the 80s. For a while I've been looking for a commercial Z8000 computer such as the Olivetti M20. They're really hard to find, but perhaps it's even more fun to build one from scratch! You'll see me assemble a pre-release version of Salvatore's pcboard, go through the various components on the board, and then boot Olivetti PCOS 4.1a. For more vintage computer projects, see www.smbaker.com/
- Наука та технологія
I had one of these computers back in the 80's, I miss that computer so much
That cut to black after the fully populated power-on gave me a heart attack 😂
I was a Z80 fanboy when I first got interested in computers and I was eagerly awaiting the arrival of Z8000 machines.... ... ... :(
Got a working M20 from a flea market for 30€. Sadly without the monitor but I'm able to use it with MDA monitor.
How do you make an M20 work with a PC MDA monitor?
@@GianmarioScotti By making an adapter. The sync signals are close to a MDA ones, just need a CRT with VSync and HSync potentiometers. The one I used is from Tulip PC ( a dutch PC XT clone).
@@RetroNora7734 yes, I want to make that adapter, but I don't know the pinout of the M20 monitor connector. Could you please help me out?
My dad knows the Salvatore person
Hi Ayush, sorry I missed you yesterday!
Dual-ported RAM and a CPLD is all it takes to implement VGA? Not even an FPGA? I'd really like to know more about this solution. I am amazed.
For your info, there are three important proprietary boards from Olivetti for the M20. The IEEE488 who was using the Intel chipset 8291, 8292 and two 8293. This is supported natively by Basic using specific commands. Another was the double serial boards with two 8251. The last was an 8086 board designed by Tecmar, who allows to use a very primitive version of MSDOS, CPM/86, etc. This board does a trickt startup sequence to gain control of the machine. A sound speech board would be wonderful, but also a Covox speech thing would be nice, too. Maybe a joystick. My dream would be to have a unique expansion board having a joystick interface for a PC like joystick (based on NE558). A double DAC or R/2R network so synthesize the speech or digitized sounds. Finally, a more evolved OPL2 or better OPL3 sound chip from Yamaha with improved FM synthesis. OPL4 based on YM278 would be a dream but it's impossible to find those chips anymore. If anybody has questions on the M20, let me know. You can find the schematics on those boards online. Just search for z80ne and M20 on google. The tricky thing of the floppy format for the M20 is that the first sector of the disks is FM, 128 bytes sector size. Floppy disks without this sector format cannot be used. That is why there is a special configuration on flash floppy to allow this weird initial sector.
Great info, thanks!
Great project!!!
Very cool project. Does Salvatore have a site available where more info might be available? Nice to see something like this that seems to work without a lot of hassle.
The only tricky thing is the regulations to the floppy interface. You need to have an oscilloscope or logic state analyzer to configure the floppy controller pulses and frequencies correctly. There are two trimmers and a variable capacitor.
Two serial chips is because one is for the serial port on the back, the other is for the keyboard, as in the original M20 the keyboard is connected to a serial port at TTL levels. As for my suggestion to Salvatore, he actually added a 6 pin header to connect the original keyboard from M20, to enjoy the specific layout for M20, but the TX/RX keyboard pins are reversed on this initial version of the motherboard. This will be fixed in the next version, together with other small defects. You can use either an M20 original keyboard connected to the 6 pin header close to the ATX power connector, or a PS2 keyboard on the PS2 connector on the back. There is the need to change two three-way jumpers close to the PIC, PS2 connextor and the CPLD chip, in order to select which keyboard to use. I also gave some advices to Salvatore during the development and I was testing on one M20 taken from my large collection of M20. We troubleshooted together and I tested the interface to IDE compact flash on the real M20. Great project. Salvatore is one of a kind and very knowledgeable. I wish I could have 10% of his skills. I confirm the holes are perfect for the ATX case. I didn't test the original M20 expansion boards and if they fits in the spaces on the ATX case.
What about getting an old OLIVETTI BCS M3030 but it you will have to take the back of the desk style machine and remove all the electronics and fit your new board and associated electronics.
I think it would be cool to build a dedicated serial terminal for use with retro projects. It would be all in one, looking something like a TRS-80 Model III or HeathKit terminal. VGA video is okay, though a touch too modern, close enough I guess. The device would be operating systemless. Instead of booting into an OS, it would boot directly into terminal emulation software. Build a retro looking terminal case for it, as you said, and there you have it. Anyway, the point is that because this board has integrated VGA output, it could be a good platform for such a project.
Is there a link to the PCB creators project, you could share?
hi, nice demonstration of this board/ just one question could you point me to those HD boards you shown?
Modena Italy.
Why didn't they have a command like diskcopy a: b: enter
Don't know why the VGA is running so slow is there a multiple that will let it run faster to a more normal rate.
You mean the scrolling speed? The vga output is perfectly fine, driven independently by a PLD from dual ported ram. The slow scrolling speed is due to the fact that the M20 had only a graphics mode. Scrolling is implemented in the BIOS and PCOS by moving memory blocks.
@@salvatorepaxia9535 Not the scrolling speed but the speed of operation of the VGA subsystem.
21:33 Don't copy that floppy.
I can't help but wonder what the world would be like if we hadn't used Intel CPUs for PCs with its terrible segmented architecture
Unfortunately the memory architecture for this processor is even uglier😀
The Z8000 segmentation actually makes Intel’s scheme look good.
There’s a reason why the Motorola 68000 family was so popular with the Unix vendors (and Apple) in pre-RISC days.
I would like to buy motherboards with Zilog Z80 8 bits; Zilog Z8000 16bits; Zilog Z80000 32 bits Best Regards, Paolo Del Bene (elpablo71)