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The 8bit Guy "Dream Computer"


Larry

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I watched part 1 and more recently part 2. I think that using a FPGA for video and audio makes most sense. I was also surprised that he was having problems getting it to run at more than 4 or was it 8MHz? That's a good reason for kicking into touch the old 8 bit I/O chips and using the FPGA to emulate them. I have a number of projects part-completed (?) in which I use 1) a real CPU 2) a large SRAM (non of this DRAM complexity) 3) a FPGA to implement I/O. One is my attempt at an Acorn Atom (with 16MHz Western Digital CPU) [working but incomplete], another my Atari-ST clone [which runs/boots EMU-TOS but lacks I/O such as keyboard or mouse at present], and another is an Atari 8-bit project.

 

Anyway I look forward to seeing where this goes, but since it is heavily Commodore, my interest ends there.

--Atariry

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3 hours ago, atariry said:

Wow! I like this. FPGA based and open source. It may be possible to re-program the FPGA to emulate an Atari 8-bit. I did a quick search for the sources and they appear to be on GitHub. I might try to see if I can port them to one of my own FPGA boards. Thanks for the heads up!

 

Yes, a real dream computer ? And it seems there are now 12 pre-series machines:

 

image.png.9d29e4ec790228ee09c03c99b36f0029.png

 

What they say about opening up to other systems  (Aug 21st 2019):

 

Quote

 

Our goal is the release of the MEGA65 with close to 100% c65/c64 compatibility.

Even to reach this goal, we need to invest alot of time already.

But like you've already mentioned, it is possible to develop an Amiga or MSX core, but it will not be done by us.

But since it is open-source, whoever is interested could port/build a core him-/herself.

The FPGA has alot of space and the MEGA65 hardware specs are impressive and easily capable of i.e. an Amiga core.

SO the sky is the limit.

 

 

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1 hour ago, atariry said:

I watched part 1 and more recently part 2. I think that using a FPGA for video and audio makes most sense. I was also surprised that he was having problems getting it to run at more than 4 or was it 8MHz? That's a good reason for kicking into touch the old 8 bit I/O chips and using the FPGA to emulate them. I have a number of projects part-completed (?) in which I use 1) a real CPU 2) a large SRAM (non of this DRAM complexity) 3) a FPGA to implement I/O. One is my attempt at an Acorn Atom (with 16MHz Western Digital CPU) [working but incomplete], another my Atari-ST clone [which runs/boots EMU-TOS but lacks I/O such as keyboard or mouse at present], and another is an Atari 8-bit project.

 

Anyway I look forward to seeing where this goes, but since it is heavily Commodore, my interest ends there.

--Atariry

I wondered about why he was having problems with 8MHz myself.  
Maybe one of the parts on the prototype was too slow?
 

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11 hours ago, JamesD said:

I'm pretty much regurgitating his argument.
My argument is that it's his project, so he can do whatever he wants.  If you don't like it, don't buy it. 
Since you know so much, make your own.  If your's is better, maybe more people will buy it.
 

That sounds way harsher than I intended.  
If you have a lot of experience, this may look pretty easy, but keep in mind, he probably hasn't designed a computer before, and I'm not sure exactly what his electronics background is either.
 

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1 hour ago, JamesD said:

That sounds way harsher than I intended.  
If you have a lot of experience, this may look pretty easy, but keep in mind, he probably hasn't designed a computer before, and I'm not sure exactly what his electronics background is either.
 

He has said in other videos that his electronics expertise isn't great, and that might explain his squeamishness somewhat.  But he's also enlisting the help of people who have more experience, so it's still kind of a head scratcher.  I like that he wants a computer that can be understood from a hardware standpoint, but it wouldn't take long to explain to him how the needed electronics work.

 

I also understand that he didn't like the idea of a board populated so much by FPGA's.  Certainly, if you want to make a computer Ben Eater style, you're going to use commodity parts that have definite purpose.  Then you can point to a chip and say "This chip is responsible for this function."  If you know the system well enough, then when something stops working you can often zero in on the cause instead of doing a blind chip swap until the problem disappears.

 

But a counterargument is that if you want a tinkerer computer, a FPGA makes sense because it can be easily updated or reprogrammed, so you don't need a huge cache of logic ICs and you don't have to redesign the PCB for a simple circuit change.  For instance, if he was willing to concede to an FPGA for the glue logic, it could house the multiplex logic needed for the CPU, the address decoders for special I/O, etc.  Of course then he'd have to learn Verilog or whatever the preferred language of the manufacturer is, and that may be more than he wants to do for a toy computer.  But in my case, learning itself is often the end goal of any of my projects, since I have no imagination for what to actually apply that learning towards (other than helping other people achieve their goals).

 

Anyway, my point boils down to, he castrated the address space over some logic that he didn't want to add, and ended up adding more logic to make up for the deficiencies.  If he wasn't already preparing for a "final product", and if I had any sway in his project, I'd definitely be making that objection known.

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8 hours ago, atariry said:

Wow! I like this. FPGA based and open source. It may be possible to re-program the FPGA to emulate an Atari 8-bit. I did a quick search for the sources and they appear to be on GitHub. I might try to see if I can port them to one of my own FPGA boards. Thanks for the heads up!

I’m already sold on these.. if they can pull double duty I’m definitely sold.

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2 hours ago, ChildOfCv said:

He has said in other videos that his electronics expertise isn't great, and that might explain his squeamishness somewhat.  But he's also enlisting the help of people who have more experience, so it's still kind of a head scratcher.  I like that he wants a computer that can be understood from a hardware standpoint, but it wouldn't take long to explain to him how the needed electronics work.

 

I also understand that he didn't like the idea of a board populated so much by FPGA's.  Certainly, if you want to make a computer Ben Eater style, you're going to use commodity parts that have definite purpose.  Then you can point to a chip and say "This chip is responsible for this function."  If you know the system well enough, then when something stops working you can often zero in on the cause instead of doing a blind chip swap until the problem disappears.

 

But a counterargument is that if you want a tinkerer computer, a FPGA makes sense because it can be easily updated or reprogrammed, so you don't need a huge cache of logic ICs and you don't have to redesign the PCB for a simple circuit change.  For instance, if he was willing to concede to an FPGA for the glue logic, it could house the multiplex logic needed for the CPU, the address decoders for special I/O, etc.  Of course then he'd have to learn Verilog or whatever the preferred language of the manufacturer is, and that may be more than he wants to do for a toy computer.  But in my case, learning itself is often the end goal of any of my projects, since I have no imagination for what to actually apply that learning towards (other than helping other people achieve their goals).

 

Anyway, my point boils down to, he castrated the address space over some logic that he didn't want to add, and ended up adding more logic to make up for the deficiencies.  If he wasn't already preparing for a "final product", and if I had any sway in his project, I'd definitely be making that objection known.

Small FPGAs aren't that expensive, but as the number of pins and/or LUTs go up, so does the price.
The multiplexed circuit requires 8 inputs (D0-D7), 8 outputs (A16-A23), and a trigger line.  
The video chip is going to need the data input lines anyway, so it would only need 9 more lines to add that... but it might only make $$ sense if there were already that many unused lines.

If I were to build a machine, I'd probably go with all FPGA myself, but as you say, he seems to want something where you can point to the CPU, point to the sound chip, point to the graphics chip, RAM, FLASH, etc...

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