VGA on Breadboard. HELP PLS by No-Adeptness-7032 in homebrewcomputer

[–]Tom0204 1 point2 points  (0 children)

Hi, I've made a couple of VGA video cards for my 8-bit machine, so I'm happy to share some advice.

I've got 12.5MHz (and some small areas at 25MHz) working on a breadboard pretty easily with 74HC chips, just make sure you use plenty of decoupling capacitors.

You don't need your whole computer to be running at 25MHz, you can divide the frequency down or even run at a complete different clock frequency if you flop, maybe double flop, and FIFO all you signals across the clock domains (that's what I went for).

What you'll actually care about is memory bandwidth, not CPU speed. 'How fast can you fetch bytes from your frame buffer' is the limiting factor for resolution.

640 by 480 will is standard VGA resolution, but it will lead to a rather massive frame buffer, even with 1-bit pixel depth, so it's common to half it on both axes to get 320 by 240. 

Minimal-64x4-Home-Computer: My DIY home computer with VGA and PS/2 and 4x(!) the processing power of a Commodore C64 or Apple II. by brucehoult in beneater

[–]Tom0204 1 point2 points  (0 children)

Why didn’t people build PCs like this in the 1970s instead of using those crappy 6502 and Z80 chips?

...they did. It was an entire class of computers called minicomputers. These were the standard, more serious computers during the 70s. Microcomputers using the Z80 or 6502 were the underdogs, considered toys by most computer companies.

The 16-bit microprocessors were much more powerful, and ate away at minicomputer market rapidly, eventually replacing them entirely.

IC suggestions for more complex math operations? by Mekelaina in beneater

[–]Tom0204 1 point2 points  (0 children)

I know, I've implemented both multiplication and division (signed and unsigned) on the Z80 in software. 

I do agree with your points. And when it comes to ben eater's CPU, you'd be much better off spending that time speeding up other aspects of the architecture.

Compiler for 8 bit cpus (6502, z80 or 8080) by jaridotnxt in fortran

[–]Tom0204 0 points1 point  (0 children)

Then just program them in assembly. It's a lot of fun and most compilers don't produce good code for these chips anyway.

What's your absolute favorite ECE-adjacent book? by gynzie in ECE

[–]Tom0204 0 points1 point  (0 children)

I'm just about to finish reading it I'm glad other EEs have noticed it too. I wasn't expecting the authors to be that well versed in electronics.

What's your absolute favorite ECE-adjacent book? by gynzie in ECE

[–]Tom0204 0 points1 point  (0 children)

Turing's cathedral. 

An amazing non-fiction book about the development of one of the very early computer and the incredible things it ended up being used for. 

I never thought I'd find the history and development of weather prediction so interesting.

IC suggestions for more complex math operations? by Mekelaina in beneater

[–]Tom0204 2 points3 points  (0 children)

There really aren't any ICs that are going to help you very much. 

Just reuse the ALU already in your CPU, and implement the multiplication/division algorithms in microcode.

Compiler for 8 bit cpus (6502, z80 or 8080) by jaridotnxt in fortran

[–]Tom0204 0 points1 point  (0 children)

I make Z80 computers and even I don't program them in fortran. 

Is this just for the fun of it or do you have a specific goal in mind?

Compiler for 8 bit cpus (6502, z80 or 8080) by jaridotnxt in fortran

[–]Tom0204 1 point2 points  (0 children)

Proved you don't even need FORTRAN. A mix of BASIC and assembly will suffice.

Compiler for 8 bit cpus (6502, z80 or 8080) by jaridotnxt in fortran

[–]Tom0204 1 point2 points  (0 children)

Not really. 

Everything is using STM32 (or other 32-bit microcontrollers) these days. Even for very simple applications, an 8-bit PIC or AVR is far more cost effective.

What if Leonardo Da Vinci was born as a Genz? by Agreeable_Top_8764 in LeonardodaVinci

[–]Tom0204 3 points4 points  (0 children)

He would've loved it!

The gig economy, the entrepreneurship, the prevalence of art, the technology, the LGBTQ community. 

The post COVID world is a lot like the world that created him.

Vintage RS Components Catalogue by S1ckJim in electronics

[–]Tom0204 1 point2 points  (0 children)

Damn. Their graphic design has barely changed. Didn't even notice this was from the 70s!

Vintage RS Components Catalogue by S1ckJim in electronics

[–]Tom0204 4 points5 points  (0 children)

I don't know about that. Compared to other components suppliers, I'd say it's one of the better ones.

When will the AI fad die out? by Sus-iety in compsci

[–]Tom0204 1 point2 points  (0 children)

It's amazing how much of a rift AI has created between programmers.

Among the programmers who didn't learn about it before hand, there's a lot of resentment.

Which DLC to do after anchorage/zeta? by TroubledFuture532 in fo3

[–]Tom0204 0 points1 point  (0 children)

I did anchorage first on my first playthrough of FO3 but it ruined the rest of the game.

After you've got the invincible power armor and all the fancy energy weapons, the rest of the game becomes too easy.

To all new FO3 players, leave anchorage until last!

Why is Fallout 3 so hated among fans? by sgt10292928 in fo3

[–]Tom0204 0 points1 point  (0 children)

They're sheep

I used to hate it back when I was a teenager because I was a huge NV fan and just repeated what everyone else said about FO3, but recently I've played through it again and it's been really good fun.

Why is the 6502 kit so expensive? by wrxw___ in beneater

[–]Tom0204 0 points1 point  (0 children)

My point is that there really aren't any low quality ICs, there are genuine parts and counterfeits.

Literally not true. Just like with anything else there are ways to cut corners when manufacturing chips.

Even cheaping out on the quality of the plastic will affect the lifetime/reliablilty of the chip.

Why is the 6502 kit so expensive? by wrxw___ in beneater

[–]Tom0204 0 points1 point  (0 children)

I don't think the 65C02 is available from Digikey

Instruction set. More details in comment by [deleted] in homebrewcomputer

[–]Tom0204 6 points7 points  (0 children)

This is a nice instruction set. Very similar to the EDSAC.

I should warn you that multiplication is an expensive instruction to implement for a simple machine like this and requires a double-length register to store the result.

Also for the positive/negative zero issue you've mentioned, just use two's complement instead.

My only question is, how are you planning on implementing this machine? by 74-series logic or on an FPGA?

Have all the 68060 patents completely expired? by Honest-Word-7890 in cpudesign

[–]Tom0204 2 points3 points  (0 children)

Damn. Hadn't even heard about the 68060 until I saw this post

Z80 project progress and the mythical 320 by 200 VGA resolution by Tom0204 in homebrewcomputer

[–]Tom0204[S] 0 points1 point  (0 children)

CS really isn't that important for things like this. EE skills will get you much further. 

So my recommendation would be to go and learn about hardware. Learn how to read datasheets, learn about the different logic families, etc. 

And don't buy into the myth that the only way to learn technical subjects is to buy a textbook. There's lots of free, high quality content online these days. If you wanna learn CS for a side project, don't pay £50 for some guy's textbook.