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Write up of my homebrew CPU build

willwarren.com

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Re: Write up of my homebrew CPU build

#11

Post by jacquesm »

Hi Will, absolutely amazing this, I love the 'money shot' up front, there are days my desk and yours could be swapped without either of us realizing right away what happened.

The Rigol deserves a blog post of its own, I've got one too and the better I get in using it the more I'm amazed at what it can do.

I've run into the same 'all you can get is SMD' which is fine for when you're finished but a lot harder while you're still figuring things out. This is where 'proper engineers' can go straight to the finish line and I always struggle.

You also develop some kind of sixth sense for when something is misbehaving. If you haven't read it yet, 'The Soul of a New Machine' might be to your liking.

best of luck with your project!

Oh, and I did read all the way to the end.

Re: Write up of my homebrew CPU build

#17

Post by fc417fc802 »

komali2 wrote: post #5

> It’s a standalone tool that lives outside the computer. I put the EEPROM into the socket, and connect via serial to my laptop to upload the binary files. Huh, I guess I never really thought about it, but how did they program the first CPUs? Like how did they overcome the chicken/egg situation?

He says that's for microcode ROMs though? As opposed to a user program written in machine code that you would use the CPU to execute. I don't believe ancient CPUs had microcode. Everything was implemented in hardware.

Re: Write up of my homebrew CPU build

#19

Post by jacquesm »

fc417fc802 wrote: post #17
komali2 wrote: post #5

> It’s a standalone tool that lives outside the computer. I put the EEPROM into the socket, and connect via serial to my laptop to upload the binary files. Huh, I guess I never really thought about it, but how did they program the first CPUs? Like how did they overcome the chicken/egg situation?

He says that's for microcode ROMs though? As opposed to a user program written in machine code that you would use the CPU to execute. I don't believe ancient CPUs had microcode. Everything was implemented in hardware.

What you believe doesn't really matter.

Plenty of 'ancient' CPUs had microcode.

68K, System 360, Sperry 1100, and even the 'ACE' to name the great grand daddy of them all had microcode.

Technically the 6502 and the 6800/09 did not, they used a dedicated decoder that was closer to a statemachine than microcode, even though both were implemented in hardware.

None of the smaller CPUs had 'loadable' microcode, but plenty of the larger ones did.

Re: Write up of my homebrew CPU build

#20

Post by mrgaro »

fc417fc802 wrote: post #17
komali2 wrote: post #5

> It’s a standalone tool that lives outside the computer. I put the EEPROM into the socket, and connect via serial to my laptop to upload the binary files. Huh, I guess I never really thought about it, but how did they program the first CPUs? Like how did they overcome the chicken/egg situation?

He says that's for microcode ROMs though? As opposed to a user program written in machine code that you would use the CPU to execute. I don't believe ancient CPUs had microcode. Everything was implemented in hardware.

CPU's microcode can be surprisingly simple: The CPU has bunch of internal signals, which activates certain parts of the CPU and the logic when to turn each signal on comes from reading bunch of input signals. The microcode can be just a memory where the input signals are the memory address and the output is the control signals.
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