a DIY home build project...

The Thor, Aurora, Q40, Q60 & Q68 etc. are discussed here.
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Ruptor
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Re: a DIY home build project...

Post by Ruptor »

Thanks for the summary I am sure it will help other newbies to this site to understand the state of play. :) I tried reading all the threads but they were very long wish lists and I couldn't see final specifications it was just too complicated for my poor little brain. :?


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Pr0f
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Re: a DIY home build project...

Post by Pr0f »

Being a DIY project, the wishlist and final specs have moved a little bit, but I have maintained as much of the spec as I can. i see it as a vehicle for using up an old case that I butchered some years back, and for testing some interface ideas - as things begin to form into tangible hardware i will add diagrams, code, pictures etc.


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Pr0f
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Re: a DIY home build project...

Post by Pr0f »

Well - time for an update on this - it spec creeped - I knew it would.

The DUART became a Quad Uart - 2 for the ser1 and ser2 ports at the back - they will be fully wired 9 pin D connectors.
The other 2 ports - one will be used as a high speed serial connection via a USB transceiver chip - for interfacing to PC / Whatever you want, and the other port is just RAW TX and RX (buffered by TTL) and output on the expanded ROM connector - this will provide part of the "Arduino" interface that will allow most if not all of the plug in cards to be placed on it - it just plugs in the new ROM port connector area. The first 2 serial ports offer both hardware and software handshaking and 64 bit FIFO's - the other 2 offer Software or none - but I may see if hardware handshaking is needed or required - some character drop tests and BERT tests needed. But 115K is not an unreasonable expectation...

I dropped the idea of using a 68008FN10 52 pin chip - and decided on a 68SEC000 - so the design has become 16 bit ROM, 16 bit Memory (4MB expandable to 15MB) and 16 bit IDE and Video interfaces. The edge connector can take any QL card as long as it doesn't use the E signal, but it will find itself at a different address, or can take a 16 bit card for future expansion / tinkering / processor upgrade. The CPU will have selectable clock from 7.5MHz to 32MHz. All memory apart from the video RAM is static.

The propellor has gone as the IPC and will be replaced with a 68K code compatible device with it's own separate 128K RAM x 16 bits, and will share a dual port RAM with the QL main processor - the bottom 8K of this space is read only for the coprocessor and will effectively look like ROM, and the upper 8K is shared RAM that both sides can read and write - this will be the new co-processor interface. Timing critical routines like the physical QL Net can now be run in the co-processor - which isolates them from CPU speed changes. The 2 processors can communicate with semaphores and interrupts to pass 4 bit nibbles / 8 bit commands or even 16 bit data to each other in a responsive manner.

The ZX8302 gets to come back as well - but will no longer be used for the RTC, the Serial transmit ports, and most of it's interrupt duties are taken over by another chip - it will just handle the Microdrive or Microdrive replacements - it will be clocked at 7.5MHz to avoid any problems with it - I still have some thinking to do around CPU speed changes - as the Microdrive code has some.

More to come soon after some further testing and head scratching


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Peter
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Re: a DIY home build project...

Post by Peter »

Pr0f wrote: Fri Oct 27, 2023 2:20 pm The propellor has gone as the IPC and will be replaced with a 68K code compatible device with it's own separate 128K RAM x 16 bits, and will share a dual port RAM with the QL main processor [...]
Device = FPGA?


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Pr0f
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Re: a DIY home build project...

Post by Pr0f »

no - not this one - I am keeping that under my hat for now - but the concept is looking good. Not a 68070 though


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Peter
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Re: a DIY home build project...

Post by Peter »

If it is to be 68K-like but no FPGA, a Coldfire V1 Microcontroller would be a cost effective, relatively modern IPC "solution" with small size/pincount options.
Not knowing the specs, I'm not sure if an IPC solves more problems than it creates extra work. ;)
E.g. the Q68 does not have an IPC to keep complexity down, and it still was more than enough work...


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Pr0f
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Re: a DIY home build project...

Post by Pr0f »

I see this as a tradeoff

I wanted the ability to change clock speeds on the QL - that meant that any timing critical code would need to be catered for. I suspect part of the reason for having the IPC in the first instance was to move mundane, repetitive and time critical (serial and sound) routines to another processor to handle. Keyboard is not so time critical, but multiple key presses and missing key presses due to not having a sufficiently large queue or returning to it frequently enough to empty it - can introduce some timing concerns.

The problem with the design is the interface between the IPC and the QL's main processor - it's slow and it can be tripped up rather too easily. It also really constrained the serial interfaces on the QL design.

I actually like the concept of the IPC - just not the implementation. And whilst it may be a bit 'overkill' the idea of having a 68K code compatible processor as the IPC means that code for it can be more easily developped, and it can be updated via the QL itself.

I spent the weekend going over the Video design again, and wondering what tricks I can use to put this in the least amount of logic. Slow progress - but some progress.

I believe I have finally managed to separate out Physical resolution and Logical screen resolution, using only 2 different dot clock frequencies - and providing either a 1024x576 resolution or a 1024x768 resolution on the physical side. I need to test these out on my different VGA monitors and with a VGA to HDMI converter to see whether these resolutions work well.


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Peter
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Re: a DIY home build project...

Post by Peter »

Pr0f wrote: Mon Oct 30, 2023 11:12 am I see this as a tradeoff
Yes it is a tradeoff between complexity and time. This project started almost six years ago, so where do you want to be in another six years? As far as I can remember, only one person managed to finish QL-style mainboards with both graphics and CPU since 1987. All these mainboards had a less complex system structure than your current project. Still they were at the limit of what is achievable, even with a lot of passion. Speaking from that experience, I would - with all respect - say you need to simplify things if you want completion within the foreseeable future. That said, I'm not sure completion is your project goal. It is absolutely fine to have fun just planning an architecture. By the way: Simplicity was very much SInclair-style according to Sir Clive, may he rest in peace.


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Pr0f
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Re: a DIY home build project...

Post by Pr0f »

My one great failing is I start many projects and run them concurrently, rather than just stick to one - so that 6 years may only have been 1 years of actual work testing out ideas and building little side projects to test those ideas.

I do finish some - but for me the journey is the fun part. I have several z80 / z180 and even ez80 machines that are up and working - but I don't use them day to day - the fun was in building / designing / hacking / troubleshooting them.

In 6 years - I hope to be retired and with a lot more time to dedicate to such things ;-) But my other half may have other ideas...


Derek_Stewart
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Re: a DIY home build project...

Post by Derek_Stewart »

Hi,

I took Voluntary Redundancy, 10 years ago from National Grid, thinking lots of time to do the things I did not have time for.

But I still have many hardware and software started and not completed.

I do not know where the time goes and how I had time to work 40 hours a week.


Regards,

Derek
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