Article View: alt.folklore.computers
Article #623882Re: What microprocessor is more powerful, the Z80 or 6502?
From: Jon Elson
Date: Sun, 10 Jun 2018 04:15
Date: Sun, 10 Jun 2018 04:15
28 lines
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3072 bytes
Andreas Kohlbach wrote: > Back in the late 70s and mid 80s you could chose between a Z80 and 6502, > when it came to 8-bit home computers. Sure there where some micros using > a M6809 (almost 16-bit) and some 8080 CPUs. But most of the micros then > ran a 6502 or Zilog Z80. > > Which one is more powerful, not regarding custom chips taking load off the > CPU, like early "GPUs" chips in the Commodore 64? > > I say the Z80 was. It could pair some 8bit registers to 16bit > entities. It also already had some kind of primitives like the later 8086 > and all future microprocessors had the 6502 lacked, speeding up things > and made programming in assembly easier. Yes, the Z80 had a lot of extra features related to handling 16-bit values. You could do some 16-bit arithmetic, it had 3 16-bit index registers that could be used as pointers to memory. One instruction group I used a lot was the INIR/OUTIR group. You could set one of the 16-bit registers as a memory pointer, and one as a counter, and then execute one of these instructions. By manipulating the WAIT signal, you could have it transfer an arbitrary number of bytes from one I/O register to a block of memory. It was essentially a CPU-driven version of DMA, with no extra hardware needed. I used it in mag tape controls, SCSI disk interfaces and a bunch of other places. No other 8-bit CPU had a feature like this. Jon
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