🚀 go-pugleaf

On Sunday, June 10, 2018 at 12:15:10 AM UTC-4, Jon Elson wrote:
> 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.

In reading the detailed descriptions above the innards of the 
respective chips, the manual for the IBM 603 electronic calculator
comes to mind.  This manual, available on the IBM website, describes,
in detail, the circuitry and functionality of the machine.  Worth a
look.  (The 603 was IBM's first mass produced electronic calculator,
a predecessor to the very popular 604.)

https://www.ibm.com/ibm/files/D165357D44082B98/us__en_us__ibm100__603calc__603_manual.pdf