The boards look well done, using modern parts and layout rules.
Ignoring rom and ram used, could the design fit using thru the hole
parts and PCB layout rules from the 70’s as Altiar 8800 rebuild.
When memory became cheaper, many 8 bit micros used what they couldn’t conveniently address directly as a RAM disk. Compared to floppies this made multi-pass tools with intermediate files a lot faster. If your disk is a SD card, on the other hand, it probably won’t help much.
What 8 bit micro’s? With 8 bitters having dual floppies was dreamt about
in the future in my life time. Today most development is done on larger host computer so slow sellf compiling is not a issue for a z80 or 6502.
Most CP/M systems had dual floppies - maybe not in '75 but towards the end of the 70s. Commodore PETs could have them, as could the Apple II and TRS-80 systems. Latterly in '81 we even had 8-bitters with not only dual floppies, but hard drives and networking capability (BBC Micro for example)
Compilers for C, Pascal, BCPL and others were usable too.
-Gordon
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I had a Coco II. I did have a s100 kit once until the power supply toasted
it. By then I moved to PC’s. Single SD card slots seem be the norm today
for retro. CP/M was east to port as well flex (and clones). Now days you are given a url (often broken) and that is your support.
Hi Ben, since you’re interested in PCB layout, I made a snapshot of the new pcb here:
And yes, it could be changed to thru-hole parts and smaller memory. For a 8080, you only need a single microcode page, that is 3 x 8 kByte. With some tricks, the microcode could even be smaller than that.
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I could never solder that, I need thru the hole parts. Looks very impressive.
Hi all,
I said, a few mails ago, “I decided against it”. Well that has changed. In the processor, you can now set independent banks for code and data. See it here:
Happy hacking !
It seems a little complicated to use, but well worth it to have this functionality without extra chips. After all, everyone always praises the very convoluted bitmap schemes of the Apple II and many great applications were made using it.
Hi, I finally ordered the new pcb, from PCBWay, the well known manufacturer of high-quality pcb’s. They were so kind to sponsor my pcb’s. See my Hackaday log for a 3D pcb view and list of changes.
I have had good luck with them and reasonable shipping costs.
It takes about a week for them from sending the gerbers to the package
at my door.
Do you have any hard to find TTL parts?
My current project needs TTL 16x4 rams.
How hard is the wi-fi interface to use?
Hi Ben,
All parts are selected for good availabilty. Everything can be bought at a single location (Mouser.com). The TTL IC’s in SMD are a lot cheaper than the DIL parts.Mouser has in general thousands on stock of any of these IC’s.
I did not yet use the WiFi interface (It’s only 3 euro at Mouser). The WiFi module is programmable, but I don’t want to make my project bigger than it already is by learning how to program the ESP8266. I plan to use the async serial interface that is already in the device . So I have a Rx, Tx. I also use RTS, so I can have timeslots that are solely for the Wifi, in which I enable the WiFi output with RTS.
The TTL IC’s have 0.05" spacing (1.27mm) and are not that difficult to solder. It’s actually easier to solder than DIL, because you don’t have to turn the board every time to solder at the back side. You can use a magnifying glass or multimeter to check for shorts.
Sometimes you find a short, but the pins are actually connected to the same net. To prevent confusion, in my board design the connection between such adjacent pins is not below the chip, but just outside the footprint, so it is clearly visible that the pins are connected by a trace.
Hi all ! It’s time to give an update.
I received the new pcb from PCBWAY several months ago. I’ve been busy with getting all new features to work, and the hardware works without a problem.
On my Hackaday page I announced there will be a KIT. You simple buy a pcb from me, for 30 Euro, and I give you the list of parts (parts will only be around 65 Euro) that you can buy at a distributor. The pcb is already available now (since I always get more than 1 pcb when I order a prototype).
A description of “which parts go where” is also available.
I also plan to make a nice document with building instructions.
Description of several software things that I did is found in the logging on my Hackaday page.
At the moment, work is going on to put a very nice operating system on Isetta. It is a pre-emptive multitasking operating system with GUI. It can be operated with a mouse:
SymbOs is available for seven different Z80 platforms. There are more than 70 applications, and the newest SymbOs 4.0 even has a spreadsheet ! For making your own programs, there is a development system similar to visual-basic (called Quigs), a C compiler, and you can program in Z80 assembler.
On Youtube there are many demonstration videos. You can also try it yourself, with this online simulation of an MSX Z80 computer:
(In the demo, you see two mouse pointers. Click the middle mouse button to have only the SymbOs mouse, click again to have your PC mouse back).
To me, this looks like the most complex Z80 program ever made. I will have to overcome several obstacles before this is working on Isetta.
Happy Hacking !
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Good to hear about your progress - also good to hear that SymbOS is still actively developed. We have a discussion over here about it:
SymbOS - a multitasking OS and GUI for your Z80 machines
BREAKING NEWS
The Isetta computer can now run the SymbOs operating system ! On april 3rd, 2025 it ran the first SymbOs applications. SymbOs is a pre-emptive, multitasking operating system with graphical user interface, comparable to Windows 95. On Isetta it still has several small bugs, but these are solvable. SymbOs stores its applications and data on Isetta’s micro-SD card. Many applications take only a second to load.
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Congratulations! It is very nice to see a new computing ecosystem come to life.
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As a reminder another TTL 6502 was done years ago.
http://6502.org/users/dieter/m02/m02.htm
But that one can’t run Z80 code, so something of a different animal…