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 [ 6 posts ] 
 Your 2019 homebrew or retro CPU year in review 
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Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1666
Greetings, everyone, and Merry Christmas and Happy Solstice and so on.

We're coming up to the end of the year - it would be nice to hear your personal CPU highlights, whether discoveries you made, inventions, marathon debugging sessions, or just your favourite CPU memory of the year.

(I'll figure out what mine is and post it later!)


Sat Dec 28, 2019 10:01 am

Joined: Mon Oct 07, 2019 2:41 am
Posts: 292
I guess some sort of 6502 will make 75% of the hits of the moderm machines and a PDP8 from
the classics.


Sat Dec 28, 2019 7:30 pm

Joined: Wed Nov 20, 2019 12:56 pm
Posts: 78
For me the highlights have been:
* Coming up with the idea for the EightThirtyTwo CPU.
* Learning how to use GHDL and GtkWave to simulate a design and view traces.
* Seeing the CPU running a test program in simulation.
* See the CPU running assembly "Hello World" code on an FPGA.
* Seeing the CPU's vbcc backend working well enough to compile and run a Dhrystone benchmark.


Sat Dec 28, 2019 8:07 pm

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1666
Most of my contribution is with others, so perhaps some of my highlights are some of theirs too:
* I did my first-ever Z80 coding! A boot-loader for revaldinho's CPC-cplink invention. An interesting technology allowing a CPC to partner with a Pi (or a Teensy, or Arduino...)
* (With revaldinho) we came up with OPC-8, a 24 bit word-oriented CPU in one page
* (With revaldinho) I 'helped' with a paper and presentation on Ferranti's F100-L micro, a bit-serial-on-the-inside 16 bit word-oriented machine - we both went to Glasgow and he delivered the talk. We also had a trip to Manchester to search MOSI's archives for Ferranti material.
* for perhaps the first time, an example of Acorn's Extended (Turbo) 6502 Second Processor came up on ebay, and I had some interesting discussions with hoglet about how it might work
* we had a couple of mini-meetups at hoglet's and I was loaned an '816-based Acorn Communicator which to my shame I haven't yet investigated
* again, with hoglet, some interesting discussions and investigations with the visualZ80 transistor-level model, and variations on that, mostly in search of the 'traps'.
* and again with hoglet, some discussions and progress with his fixed-point engine for Mandelbrot rendering
* not very CPU-related but I typed in a couple of amusing Basic programs on BBC Micros at The National Museum of Computing
* also not very CPU-related but I've been running the Retrocomputing Forum to provide some sort of continuity as G+ closed
* my long-ago paid-for Spectrum Next continued to be something to look forward to. (I'm thinking of it as a nicely packaged FPGA platform with RAM and a Pi interface, rather than as a Spectrum.)


Sat Dec 28, 2019 9:40 pm

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1666
Of course if you boil down my summary you find I've written a page of code and gone on a couple of trips!

Rather more significant for 2019 is that this forum has seen some very interesting developments - more than one CPU is being actively developed, together with tooling, and we've seen half a dozen introductions and had probably a couple of dozen new members. And some very interesting discussions.


Mon Dec 30, 2019 10:02 am
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Joined: Fri Mar 22, 2019 8:03 am
Posts: 328
Location: Girona-Catalonia
For me, the list is not that long, but I will try to summarise what the year meant for me.

Having had a past of software development for industrial applications, I decided in February or so, after youtube suggested to me a video (yes, that was the spark), that I would build my own CPU. I performed some searches and decided to contact a guy who had made an impressive implementation of a 6502 only using TTL chips in a quite compact envelop. He turned out to be a respected member of the 6502 forum (I guess I don't need to explicitly mention who he is :-)). He was kind enough to introduce me to the essential hardware aspects of a CPU and TTL design by responding all my questions, and I learned a lot considering that my previous knowledge on the particular subject was almost zero.

In late March, I joined this forums with the intention to learn more, and to start sharing my own build/work. I began with what I was more comfortable with, which is defining an ISA and implementing software tools. I decided that a compiler was an essential tool to have (after all, using compilers was part of my living). Since I already implemented custom compilers in my long past, creating one from scratch again didn't appeal me much any longer, so this time I wanted to do something different such as having a go at implementing a LLVM backend. The lack of detailed documentation and rather harsh LLVM community (only helping with the very basics) caught me by surprise, but I persisted and eventually got something working at the end. I am glad I did, as during the journey I learned a lot from this particular compiler (both the good and the bad). This alone took me almost an entire year, but considering that I suffer from a painful disability, and I'm no longer a teenager, I do not complain about how long getting things done take to me 8-)

Later in the year, I figured out that I really would want to push my ISA and compiler to their true limits, and make it run at the highest as possible clock frequency, ideally not running just simple software, but "serious" stuff if possible. But I realised that I really didn't have the required skills for that (or not yet), and this would take me a long time before I would get something material. So I decided to keep that in stand-by for a while, and started (a supposedly) easier project, a relay computer, hoping to gain some of the required experience that should allow me to get back to my original project when the time is right for me.

I have too other unrelated hobbies and interests, such as Model Engineering (making small steam locomotives or engines that actually run on coal/gas and real steam) so I put some time on that too, if health allows. Ultimately, most of life is trying to enjoy ourselves, so that's what this year has brought to me, and joining this forums has been an important part of it !!


Tue Dec 31, 2019 11:12 am
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