Raven. A homemade Atari-like computer

[agranlund]

I'm still reading the data sheet of these chips as I didn't know they existing until earlier in this thread!
I know one of your stated aims was to build a machine using these chips, so I'm guessing the answer is there, but I just wonder if more modern logic would have saved some heartache here!

You may be right, I'm on the fence personally.
If you're good with and enjoy cupl/vhdl then it probably makes a lot more sense to implement your own clone in a cpld. Especially so if you're building something intended for an audience so you wouldn't have to rely on finding old stock.

To me and for what I wanted to build it felt like a natural fit to use an original Motorola family part made for this purpose.

Not sure what would have been easier. For me, I suspect I may have had to spend more time implementing a clone rather than interfacing with an original chip? The 40mhz version I bought takes well to overclocking and the later ones were obtained mostly out of curiosity (and by costing almost nothing) -- I wouldn't recommend getting a 33mhz version.

Then again, the goalpost moved a bit too. Speed was not super important but I was hoping to be able to go 50mhz cpu / 25mhz bus, but then the prototype exceeded expectations with twice that.

I'm guessing this is what the second CPLD on CT60 and the 'bus' CPLD on the TFx60 does?

That would be my guess too. The BFG9060 accelerator implements the required bus sizing logic in a cpld too.

[viking272]

The BFG9060

Is that a nod to Doom and their BFG9000!?

[Oldskool]

Not sure what do you think.
Although the letters on the Raven PCB are also somewhat doom like.
Great card for the 4000.

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Just received my second 40 mhz 68150 from the uk. ZKAC9921.
I still have the video issues with the videocard. I can’t imagine it has anything to do with the 68150 now.

[Cyprian]

@agranlund do you plan to add support for more ram e.g. 128GB?
I also wonder about memory performance. Would it be possible to get close to the CT60 memory performance?

[DrZiplok]

@agranlund do you plan to add support for more ram e.g. 128GB?
I also wonder about memory performance. Would it be possible to get close to the CT60 memory performance?

More than 48MB will require a new MLB, as the SIMM sockets only have enough address (22) lines for 16M each. You'd also need to convince @agranlund that he would enjoy designing a DRAM controller, or that in the spirit of the 68150 he should source some DP8440s and design around that.

Getting good perf out of the A1 Raven is probably possible; if you're prepared to sit down with the '060 user's manual and CUPL for a bit you should be able to make burst mode work. That's most of what's left on the table right now, AFAICT.

[Cyprian]

@DrZiplok thanks for explanation

[agranlund]

DrZiplok summed it up pretty well

I do have some very fast sram simms built that I would love to find time to play with but they are probably not super interesting for most as they're either even smaller or more expensive.
Getting around to looking at burst mode would be nice too and I'm especially curious to see what that would do in combination with those fast simms.

In theory, one could route another address line to an unused pin on the simm sockets in some new revision. And/or create and add support for some kind of combo ram/rom simm. But that feels a bit like expensive band-aids if you are looking for 128mb figures.

I'm absolutely not disputing dram is a better choice, you'd get faster, more and for cheap. All the good things.
I just didn't (and still don't) see a use-case for myself to warrant spending the time. I'll be the first to admit it's all very egoistically designed - and it probably had to be, I suspect it would have been dropped before first prototype otherwise. Of course, now that I do have the computer I wanted it's not entirely impossible to be convinced to add or change things around.


I am genuinely curious what you would run that makes use of all that ram though? And while still somehow tolerate using it on a 100mhz computer with ISA graphics

We were well on our way to 1Ghz when 128MB was a thing and your ~100mhz P1 system would have had 16MB so I thought 3x of that made for a pretty well balanced system without going far into fantasy lala-land

[agranlund]

Work in progress port of ct60conf.cpx, based on CT60 sources from Mikro's Github repo.
Only thing missing is remaking the "Boot" page with Raven boot options such as size of ST-RAM, cache modes and perhaps some other bits and bobs.
I'm thinking I'll lift the CT60 rom flashing utility as well - the logic is completely different but GUI requirements are more or less similar.

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[agranlund]

It's interesting how you get so used to stuff when they improve slowly and in small increments.
Comparing now against older photos reveals that, yes, things has indeed happened

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This must have been one of the first times I had anything on the screen. A big deal then for sure.

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[coonsgm]

I can't tell you how much I love this! I wish I had the time to build one of these up...this is just so amazing.