Trivia: the article says the Z80 had "full compatibility" with the 8080, but that isn't true. Here and there programs failed because of it.
In the 8080, most ALU operations set the "P" (parity) flag to indicate if the result had an even or odd number of 1 bits. On the Z80, that flag would be set the same way for logical operations (AND, OR, XOR), but for ADD/SUB operations it was used as an overflow flag -- not carry out, but it indicated that the 2s-complement result wasn't able to accurately represent the result.
There were also some changes in the way the half-carry (nibble carry out) flag was handled in some instructions too.
> Zilog still makes the Z80, which is used in some embedded systems.
Still used in the TI range of graphing calculators. Specifically, the TI-84 CE range[0]. I can't speak for other countries, but graphing calculators are mandatory in Dutch high schools, and the TI series is the default choice for many (I got a TI 83+ Silver Edition when I was 14, which was "new" at the time - guess my age). I suspect because it's low-powered enough to still require that students Learn The Material too (instead of doing the symbolic calculus through the calculator). Texas Instruments must be having quite a large mark-up on such a dirt-cheap piece of electronic hardware though.
Anyway, because of that, Z80 assembly was my second programming language TI Basic being the first[1]. It really is quite accessible - I mean you basically memorise the entire instruction set after a while because it's so small and simple[2].
Funny enough, I remember when moving to higher level languages that almost every tutorial that I read on warned me that pointers were really, really hard, and I couldn't see why at that point. I guess that if you start from the ground up instead from the top down, some things get easier.
> Anyway, because of that, Z80 assembly was my second programming language TI Basic being the first.
I didn't have the cable you needed to transfer binaries from a desktop computer to the calculator, and I never finished the cable I tried to build myself from scrap parts. Hence, I never got past the TI Basic, which you could program on the calculator itself. :-)
I had a similar high school experience. Not as much asm but spent way too many hours writing basic programs on that thing. prob should have spent more time listening in class.... nar! :-D
I had the TI-85, and after BASIC I learned Z80 assembly. I wrote a bunch of programs for that calculator in HS. I love it, and I still love the Z80. So simple yet brilliant.
Started coding with a Timex 2068 back in the day, and went through Z80, 8086, 68000, Basic and Pascal dialects before getting to learn C, nothing special about C pointers.
I spent many happy years making the Z80 dance, from Summer 1976 through Spring 1989, architecting and writing statistical multiplexors at MICOM Communications in LA. Micro 800 line. That is a Hard Real Time application, and the hardware for the first model was only 4KROM and 4KRAM. I made one Z80 do what the competition (CISCO) swore required 5, and laughed discreetly at us, but it worked, sold out the bottom end market from under them, and suddenly we had a runaway and I got an excellent team to buttress and ultimately take over the baton from me. I would dream in Z80 ASM in those days.
The Z80 had two hardware features that made it possible, and that nobody here has mentioned yet:
1: two sets of working registers, with a one byte instruction to toggle between them. I instruction cyclke to context switch between application and interrupt handlers. Only the TI 9900 came close with its in-RAM working register sets.
2: hardware vectored interrupt dispatch, fully suppported by theor accompanying peripheral line. Just a few clocks from raising an interrupt to executing the first line of code (typically switch context then ...) of not only the device but it's reason for interrupt code. No code wasted interrogating bitfields and scanning registers. 2 usecs interrupt response time. Faster than an Intel i960 with its 50MHz clock, that came along later.
Surprised that the TI-8X series and TRS-80 got mentioned as popular applications, but not the Gameboy! (well, it's not _exactly_ a Z80, but it's close enough that reasonable Gameboy emulators are feasible on a TI-83+SE: https://www.ticalc.org/archives/files/fileinfo/419/41990.htm...)
The ironic bit is that the emulation experience is fundamentally flawed because the TI-83+SE has a lower resolution display than an original Gameboy. The original TI-83 launched in 1996, the Gameboy in 1989.
I can testimony for Z80 assembly (tough I cannot say anything about 6502).
In high school one of our teachers made us program a Z80 board by hand.
And when I say "by hand" I mean it quite literally: first a flow-chart, then a conversion to z80 assembly (two passes: pencil first, pen later), then datasheet at hand a conversion into z80 opcodes (this time it was three passes, the third one was to recalculate all jumps, absolute and relative ones).
Last step was to input each opcode into memory by hand using an hexadecimal keypad. Then go to address 1800h, hold breath and press RUN.
In retrospect, it was a very enlightening experience considering I and my school mates were like 16-17.
But keep in mind, if a 17 years old can do this with relative ease (it was a technical high school, after all) that should tell you something about the simplicity and effectiveness of the Z80 instruction set.
It is until you start treating the 6502 as a RISC CPU with 256 registers at 0x0000. I had that “ohhhhh” moment when I had a BBC master back in the late 80s. Zero page FTW. Z80 feels like wading in treacle after that. X86 is an abomination
The 6502 is a much simpler CPU (3.5k transistors vs. 8.5k for the Z80), but the Z80 is easier to use and less limiting --- more registers and addressing modes, a stack not limited to 256 bytes and fixed location, and a more regular octal-format instruction encoding[1].
Some of this was due to syntax of their assembly languages. 6502 had letters for different addressing modes, whereas Z80 used parentheses for a memory lookup, e.g. LD A,(HL) uses HL as a pointer, loading its pointed-to value into A (IIRC).
6502 had more addressing modes, but some of them, if not all, could have used Z80 style syntax. After all, it would just be a different the assember (i.e. compiler) frontend, generating the same target machine code.
I like reading history about old chips like this, i've read about the z80 before... but where is the rest of the article? so short, the z80's story is far longer than this.
Me too, love this stuff. For those of us who haven't a clue about coding or software (I'm a retired neurosurgical anesthesiologist), reading this comments section and its ilk is like visiting the Egyptian Museum in Cairo and gazing at the hieroglyphics. My understanding of what I'm reading/seeing is nil but the wonder titer is high.
For the rest of the article start by reading https://en.wikipedia.org/wiki/Datapoint_2200
Datapoint allowed Intel to continue development with the same architecture but required all future processors to have a shuffled instruction set. The mov group on the 8008 and the 2200 was octal 3ds with d being the destination register and s being the source register. The first digit 3 got shuffled to 1. The registers were also shuffled:
8008 bits 8080
A 000 B
B 001 C
C 010 D
D 011 E
E 100 H
H 101 L
L 110 (HL)
(HL) 111 A
Datapoint did not want Intel's future processors to be able to execute Datapoint machine code. They had a lot invested in their software.
Datapoint also had a 5500 processor which was more powerful than the 2200. It was microprogrammed rather than the simpler logic decode of the 2200. It was compatible with the 2200 but had many more instructions (think Z80). Yes it was that instruction set. The engineers at Intel who worked on the 5500 design left to form Zilog.
I worked as an electronics technician at Datapoint and performed test and repair of many 2200 and 5500 processor boards including writing short machine code routines to exercise the hardware.
After I left Datapoint (1977) I worked for Tandy where I repaired thousands of TRS-80 Model 1 computer boards which used the Z80. When the Tandy engineers came into the repair area with the programmers who had written Level 2 BASIC for the TRS-80 with the first masked ROMs, they tried the ROMs on a board and it didn't work. I told them that all the boards in the area needed repair but I had one that I had just repaired. I was introduced to Bill Gates and Paul Allen and the ROMs were put on my repaired board. I typed in a one line program to count and print numbers on the screen and it worked. Bill Gates offered me a job at Microsoft which had about a dozen employees but I turned him down and stayed at Tandy. I wrote more test programs and transitioned into full-time programming.
And, then, they thought: "hum... let's do our 16 bits microprocessor... and forgot the retro compatibility with our own 8bit chip!".
What could go wrong?
The 8086 wasn't binary compatible, but it was (more or less) software compatible---you could mechanically translate 8080 assembly to 8086 assembly and get about 95% converted without issue.
Motorola broke compatibility completely when they transitioned from 8-bits (6800, 6809) to 16/32 bits (68000) [1].
[1] From a hardware perspective, the 68000 is a 16-bit system; from a software perspective, it's a 32-bit system.
z80 is a lovely instruction set, and a delight to work with. These days CPUs are incredibly complicated, with massive instruction sets, pipelining and caches, microcode and SMP, lots of crazy nonsense going on. Anyone who has ever worked with the x86 family at a low enough level knows just how insane it is. z80, on the other hand, is just a reasonably fast CPU with predictable timings and an instruction set which can fit on an index card (well, if you use both sides). It still has plenty of secrets to discover, though - easily half of the instruction set is undocumented and full of useful tricks. I have spent a lot of time with this CPU, none of it wasted :)
After suffering the gaps in 8080 command set for years, this was the greatest joy ever. Also the new assembler was such a pleasure, you could just LD everything to everywhere.
The Z80 was a contemporary of MOS Technology’s 6502, and like that chip, it stood out not only for its elegant design but also for being dirt cheap (about US $25).
Anybody got a graph of historical 6502 vs Z80 prices?
My father's first computer was a Sinclair ZX81, powered by a Z80. He still has it at home.
I tried getting it working a few years ago, but it wouldn't work with the TV. I wasn't really interested enough to get an old TV to use with it. Pretty amazing though, not many people are able to say they still have their first computer.
I still have a Timex 2048 (a clone of Sinclair ZX Spectrum). It is not the first Spectrum I used, but first I owned. It works still and I have a family tradition of plugging it into our TV set each Christmas and playing the games we have grown up with. Years ago I could use my PC workstation to "play" tape recordings into it but nowadays you have to use an Android phone [1] as I think there is too much of sound filtering built in and the tapes just don't load.
I still have my ZX81.
My dad bought it for the family when I was 11. It was to me the most anazing and fascinating thing. It absorbed my attention completely. I remember handwriting code on the bus to school.
They still manufacture z80 DIPs and it’s crazy easy to build homebrew computers with them (you really only need a few chips total to have something that works.) it’s something I think anyone that uses computers heavily should try.
[+] [-] tasty_freeze|7 years ago|reply
In the 8080, most ALU operations set the "P" (parity) flag to indicate if the result had an even or odd number of 1 bits. On the Z80, that flag would be set the same way for logical operations (AND, OR, XOR), but for ADD/SUB operations it was used as an overflow flag -- not carry out, but it indicated that the 2s-complement result wasn't able to accurately represent the result.
There were also some changes in the way the half-carry (nibble carry out) flag was handled in some instructions too.
[+] [-] slededit|7 years ago|reply
[+] [-] vanderZwan|7 years ago|reply
Still used in the TI range of graphing calculators. Specifically, the TI-84 CE range[0]. I can't speak for other countries, but graphing calculators are mandatory in Dutch high schools, and the TI series is the default choice for many (I got a TI 83+ Silver Edition when I was 14, which was "new" at the time - guess my age). I suspect because it's low-powered enough to still require that students Learn The Material too (instead of doing the symbolic calculus through the calculator). Texas Instruments must be having quite a large mark-up on such a dirt-cheap piece of electronic hardware though.
Anyway, because of that, Z80 assembly was my second programming language TI Basic being the first[1]. It really is quite accessible - I mean you basically memorise the entire instruction set after a while because it's so small and simple[2].
Funny enough, I remember when moving to higher level languages that almost every tutorial that I read on warned me that pointers were really, really hard, and I couldn't see why at that point. I guess that if you start from the ground up instead from the top down, some things get easier.
[0] https://en.wikipedia.org/wiki/TI-84_Plus_series
[1] https://www.ticalc.org/archives/files/fileinfo/328/32816.htm...
[2] http://wikiti.brandonw.net/index.php?title=Z80_Instruction_S...
[+] [-] Bromskloss|7 years ago|reply
I didn't have the cable you needed to transfer binaries from a desktop computer to the calculator, and I never finished the cable I tried to build myself from scrap parts. Hence, I never got past the TI Basic, which you could program on the calculator itself. :-)
Here's a TI Basic rendering of a sphere (the Moon seen from Earth, say): https://i.imgur.com/xWb1xk2.jpg
[+] [-] cottsak|7 years ago|reply
[+] [-] apple4ever|7 years ago|reply
[+] [-] pjmlp|7 years ago|reply
Started coding with a Timex 2068 back in the day, and went through Z80, 8086, 68000, Basic and Pascal dialects before getting to learn C, nothing special about C pointers.
[+] [-] dwarman|7 years ago|reply
The Z80 had two hardware features that made it possible, and that nobody here has mentioned yet:
1: two sets of working registers, with a one byte instruction to toggle between them. I instruction cyclke to context switch between application and interrupt handlers. Only the TI 9900 came close with its in-RAM working register sets.
2: hardware vectored interrupt dispatch, fully suppported by theor accompanying peripheral line. Just a few clocks from raising an interrupt to executing the first line of code (typically switch context then ...) of not only the device but it's reason for interrupt code. No code wasted interrogating bitfields and scanning registers. 2 usecs interrupt response time. Faster than an Intel i960 with its 50MHz clock, that came along later.
[+] [-] loser777|7 years ago|reply
The ironic bit is that the emulation experience is fundamentally flawed because the TI-83+SE has a lower resolution display than an original Gameboy. The original TI-83 launched in 1996, the Gameboy in 1989.
[+] [-] sehugg|7 years ago|reply
"Access cheap DRAM just like you do SRAM" must have been an effective sales pitch at the time.
[+] [-] raverbashing|7 years ago|reply
Yes, yes it was
[+] [-] digi_owl|7 years ago|reply
The Z80 was also a big deal in Europe, where it powered two (major) brands of micros in UK alone, and was cloned extensively in the USSR.
[+] [-] Fins|7 years ago|reply
[+] [-] dcminter|7 years ago|reply
[+] [-] megy|7 years ago|reply
Do you know what they were, or is that secret information? It wasn't the BBC micro, was it the ZX Spectrum and Amstrad?
[+] [-] thanatropism|7 years ago|reply
[+] [-] znpy|7 years ago|reply
In high school one of our teachers made us program a Z80 board by hand.
And when I say "by hand" I mean it quite literally: first a flow-chart, then a conversion to z80 assembly (two passes: pencil first, pen later), then datasheet at hand a conversion into z80 opcodes (this time it was three passes, the third one was to recalculate all jumps, absolute and relative ones).
Last step was to input each opcode into memory by hand using an hexadecimal keypad. Then go to address 1800h, hold breath and press RUN.
In retrospect, it was a very enlightening experience considering I and my school mates were like 16-17.
But keep in mind, if a 17 years old can do this with relative ease (it was a technical high school, after all) that should tell you something about the simplicity and effectiveness of the Z80 instruction set.
Z80 <3
[+] [-] setquk|7 years ago|reply
[+] [-] userbinator|7 years ago|reply
[1] http://www.z80.info/decoding.htm
[+] [-] hyperpallium|7 years ago|reply
6502 had more addressing modes, but some of them, if not all, could have used Z80 style syntax. After all, it would just be a different the assember (i.e. compiler) frontend, generating the same target machine code.
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] tomxor|7 years ago|reply
[+] [-] bookofjoe|7 years ago|reply
[+] [-] BillBohan|7 years ago|reply
8008 bits 8080
A 000 B
B 001 C
C 010 D
D 011 E
E 100 H
H 101 L
L 110 (HL)
(HL) 111 A
Datapoint did not want Intel's future processors to be able to execute Datapoint machine code. They had a lot invested in their software.
Datapoint also had a 5500 processor which was more powerful than the 2200. It was microprogrammed rather than the simpler logic decode of the 2200. It was compatible with the 2200 but had many more instructions (think Z80). Yes it was that instruction set. The engineers at Intel who worked on the 5500 design left to form Zilog.
I worked as an electronics technician at Datapoint and performed test and repair of many 2200 and 5500 processor boards including writing short machine code routines to exercise the hardware.
After I left Datapoint (1977) I worked for Tandy where I repaired thousands of TRS-80 Model 1 computer boards which used the Z80. When the Tandy engineers came into the repair area with the programmers who had written Level 2 BASIC for the TRS-80 with the first masked ROMs, they tried the ROMs on a board and it didn't work. I told them that all the boards in the area needed repair but I had one that I had just repaired. I was introduced to Bill Gates and Paul Allen and the ROMs were put on my repaired board. I typed in a one line program to count and print numbers on the screen and it worked. Bill Gates offered me a job at Microsoft which had about a dozen employees but I turned him down and stayed at Tandy. I wrote more test programs and transitioned into full-time programming.
[+] [-] MarcPereira|7 years ago|reply
[+] [-] spc476|7 years ago|reply
Motorola broke compatibility completely when they transitioned from 8-bits (6800, 6809) to 16/32 bits (68000) [1].
[1] From a hardware perspective, the 68000 is a 16-bit system; from a software perspective, it's a 32-bit system.
[+] [-] js2|7 years ago|reply
https://en.wikipedia.org/wiki/Z-80_SoftCard
My Apple II had one for basically the sole purpose of running Wordstar under CP/M (I don't recall why we didn't just use Apple Writer).
[+] [-] chadcmulligan|7 years ago|reply
[+] [-] Sir_Cmpwn|7 years ago|reply
[+] [-] timonoko|7 years ago|reply
[+] [-] glhaynes|7 years ago|reply
Anybody got a graph of historical 6502 vs Z80 prices?
EDIT: Some previous HN discussion "On choosing the Z80 over the 6502 (2014)" https://news.ycombinator.com/item?id=10763274
[+] [-] TheOtherHobbes|7 years ago|reply
[+] [-] toomanybeersies|7 years ago|reply
I tried getting it working a few years ago, but it wouldn't work with the TV. I wasn't really interested enough to get an old TV to use with it. Pretty amazing though, not many people are able to say they still have their first computer.
[+] [-] adamkruszewski|7 years ago|reply
[1] https://play.google.com/store/apps/details?id=dk.rift.tzxdro...
[+] [-] digi_owl|7 years ago|reply
I think my dad still have it in the basement, but i recall he never got much out of it.
[+] [-] Wildgoose|7 years ago|reply
[+] [-] jacquesm|7 years ago|reply
https://sewelldirect.com/composite-rca-to-vga-converter
[+] [-] DEADBEEFC0FFEE|7 years ago|reply
[+] [-] sedatk|7 years ago|reply
[+] [-] swiley|7 years ago|reply