A project log for Novasaur CP/M TTL Retrocomputer

Retrocomputer built from TTL logic running CP/M with no CPU or ALU

Alastair HewittAlastair Hewitt 04/18/2019 at 14:072 Comments

This was always a stretch goal, but it looks very doable now the design is complete... and it wouldn't be the first TTL Computer on the Internet.

What is the scope of Internet-enabled?

Connectivity is via the RS232 port. This provides an ancient but still supported interface standard. There are plenty of inexpensive options to adapt to more modern serial standards. These include USB with an FTDI cable and Ethernet with a WizNet protocol adapter. Of course, dial-up would be the most authentic method using a standalone modem.

A TCP/IP stack is a project in its own right. Something like uIP could be ported to the YATAC and would work within the constrained resources. Things like the WizNet adapter can offload some of this stack overhead and will be used to get things up and running quickly.

The simplest server/client model would be TFTP. I plan to do better than this though and go straight to HTTP with a browser and web server. However, this would be the Tim Berners-Lee 1991 version of the Web: Text only browser supporting a subset of HTML 2.0 and basic web server file handling. This will provide everything needed to upload and download programs via a web interface, so no mass storage is needed.

The hardware text mode was specifically designed to render basic web pages. The 4 fonts are used with HTML as follows:

There are 8 colors available, so links would be highlighted along with using the underline font. Headers would also be highlighted in a different color using the bold font.

Pages can be up to 256 lines long and are rendered directly to the screen memory. Scrolling is achieved by updating one register on every screen refresh. Almost no additional CPU resources are required to display a page once loaded.


Dylan Brophy wrote 04/19/2019 at 20:51 point

This will be very interesting - I can't wait to see how it goes!  Maybe if it can connect to the internet, it can be used to control things remotely?  It would be interesting to see a TTL computer used for more than a webserver too (not to say that's a small accomplishment; it isn't).

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Yann Guidon / YGDES wrote 04/19/2019 at 02:56 point

Wiznet is a good solution, you can get some decent buffering as a bonus :-)

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