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Z80 – The 1970s Microprocessor Still Alive (2021)

computer.org

11–20 of 78 posts

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#11

interesting to be reminded that an 8080 (8 bit datapath) took 4,800 transistors an Apple M5 Max is 100,000,000,000 transistors (ok it’s 18 CPU + 40 GPU cores) by comparison so 17 million 8080 equivalents

Nitpicking, but since the M5 includes cache and GPU a more realistic comparision would probably be to count all transistors in an entire 8-bit home computer system against a modern integrated GCPU (e.g. from googling around a C64 might have around 0.75 million transistors, most in the memory chips).

And in a way, those old 8-bit home computers also worked like a single integrated 'super-chip', because the whole system was driven by a single clock and entirely 'hard realtime', while modern computers are much more asynchronous (and I guess this asynchronous design is what enabled most performance improvements that go beyond pure transistor count scaling).

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#12

interesting to be reminded that an 8080 (8 bit datapath) took 4,800 transistors an Apple M5 Max is 100,000,000,000 transistors (ok it’s 18 CPU + 40 GPU cores) by comparison so 17 million 8080 equivalents

This is understandable, considering that the M5 is the Ultimate Computer, powered by Dr. Richard Daystrom's very own engrams

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#14
post #4

Due to its simplicity it's a fun little processor to program. Hacking on some assembly on a ZX spectrum emulator is a nice way to stay sane in this high abstraction LLM age.

"Simple" is really not a word I would associate with the Z80 ;) The ISA is quite messy because of the backward compatibility requirement with the Intel 8080 (e.g. the Z80 had to fill undocumented gaps in the 8080 opcode encoding map with new instructions, four of which were prefix instructions to unlock additional instruction 'subsets' (DD/FD for replacing instructions involving the HL register pair with indexed addr…

> If the Zilog engineers would have been free to design their own ISA I'm sure they would have been able to come up with a much more elegant design.

Since Zilog was founded by former Intel engineers, they were probably the ones who helped design the 8080 in the first place?

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#15
post #8

Ironically (and sadly) the Z80 was discontinued not very long after this piece was published.

I'm sure clones are still being made.

The cpu possibly, but I had a hard time trying to find the support chips (ctc, sio/pio, etc)...

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#16

interesting to be reminded that an 8080 (8 bit datapath) took 4,800 transistors an Apple M5 Max is 100,000,000,000 transistors (ok it’s 18 CPU + 40 GPU cores) by comparison so 17 million 8080 equivalents

This is understandable, considering that the M5 is the Ultimate Computer, powered by Dr. Richard Daystrom's very own engrams

excellent point

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#17
post #13

interesting to be reminded that an 8080 (8 bit datapath) took 4,800 transistors an Apple M5 Max is 100,000,000,000 transistors (ok it’s 18 CPU + 40 GPU cores) by comparison so 17 million 8080 equivalents

The ARM 1 only had 25,000 or so.

wonders how ARM did that - the MIPS R2000 came in at ~115k and the 80286 ~134k

anyway - say you want 50% of the transistors for on chip RAM these days, then thats

100 billion / 50 thousand = 2 million ARM 1s

clocking at say 3GHz

6e15 MIPS = 6 peta MIPS

so if you could run code on it, you would get a 10,000x speed up ;-)

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#18
post #4

Due to its simplicity it's a fun little processor to program. Hacking on some assembly on a ZX spectrum emulator is a nice way to stay sane in this high abstraction LLM age.

"Simple" is really not a word I would associate with the Z80 ;) The ISA is quite messy because of the backward compatibility requirement with the Intel 8080 (e.g. the Z80 had to fill undocumented gaps in the 8080 opcode encoding map with new instructions, four of which were prefix instructions to unlock additional instruction 'subsets' (DD/FD for replacing instructions involving the HL register pair with indexed addr…

I am simplifying a lot since there were much more chips involved... but 3500 transistors to have countless hours of fun to play NES games really puts things into perspective

My 5090 has 92 billion transistors (I dont say they dont bring fun)

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#19
post #13

Earlier quoted context omitted.

The ARM 1 only had 25,000 or so.

wonders how ARM did that - the MIPS R2000 came in at ~115k and the 80286 ~134k anyway - say you want 50% of the transistors for on chip RAM these days, then thats 100 billion / 50 thousand = 2 million ARM 1s clocking at say 3GHz 6e15 MIPS = 6 peta MIPS so if you could run code on it, you would get a 10,000x speed up ;-)

A fairly deep dive into it

https://www.righto.com/2015/12/reverse-engineering-arm1-ance...

Re: Z80 – The 1970s Microprocessor Still Alive (2021)

#20

interesting to be reminded that an 8080 (8 bit datapath) took 4,800 transistors an Apple M5 Max is 100,000,000,000 transistors (ok it’s 18 CPU + 40 GPU cores) by comparison so 17 million 8080 equivalents

Yup and Moore's law about transistors doubling every 18 to 24 months did basically hold, which is even more impressive.

Foreseen it was.

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