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Results tagged with z80
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user 80
The Zilog Z80 microprocessor. Prefer [game-boy] instead for questions about the Game Boy CPU nicknamed the ‘GBZ80’.
8
votes
Compressing a list of records so it can be uncompressed elementwise
for large bits of data and used to bring my old 486 to its knees, but for strings shorter than 256 bytes the transformation table is the same size as the input and that's actually reasonable even on a Z80 … Since you're on Z80, you'll probably just arrange for that tuple to be a 16-bit value which, when loaded into BC, can fall into a DJNZ loop which writes B copies of C to (HL). …
- 11.6k
34
votes
Accepted
What's the difference between "opcode" and "instruction" in this Zilog ad?
So in the advert given, they are counting the basic single-byte opcodes, plus those double-byte Z80 opcodes with ED, DD, etc prefixes. … The Z80 does not commingle constants with its instructions, so there is a simple and obvious mapping of opcodes to bytes. …
- 11.6k
26
votes
Accepted
Uptime in ZX BASIC
According to http://www.worldofspectrum.org/ZXBasicManual/zxmanchap25.html, addresses 23672-23674 contain a 24 bit count of 50Hz frame ticks in the UK. I wrote a quick program to print the values, whi …
- 11.6k
5
votes
From an electrical and software engineering perspective, ignoring available software, should...
The Z80 wins slightly in that the separate I/O space means that you can cut more corners on address decoding in simple designs—look at Sinclair computers for an extreme version of this—but for a more conventional … However, you can interface the 6522 with the Z80 if you want.
As to machine code, I have a soft spot for the 6502, but somebody used to modern systems such as x86 will find the Z80 more familiar. …
- 11.6k
10
votes
Why do C to Z80 compilers produce poor code?
On Z80, LLVM tries a different approach due to the lack of that addressing mode. … Update October 2024:
I recently revisited the Z80 backend for LLVM and tried this sample function again with a compiler built from the latest commit. …
- 11.6k
40
votes
Accepted
What is the relative code density of 8-bit microprocessors?
It is more biased towards modern architectures, but it does include the Z80 and 6502 in (some of) its results. … So if you're looking for a (popular) retro CPU with the absolute-highest code density, you want the Z80. …
- 11.6k