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Subject: Re: Another port, is it possible?

Re: Another port, is it possible?

From: Bluechip <csbluechip_at_gmail.com>
Date: Sat, 18 Aug 2007 16:59:45 +0100

At 16:15 18/08/2007, you wrote:
>Bluechip wrote:
> > At 10:47 18/08/2007, you wrote:
> >> Vladimir Pantelic wrote:
> >>
> >> > The data sheet says 8bit! There is a DSP that does the MP3 decoding and
> >> > a DMA controller, so most likely the z80 does little besides reading
> >> the
> >> > FAT filesystem and setting up the DMA to pipe data from Flash to the
> >> DSP.
> >>
> >> Actually the Z80 is an 8-bit CPU with some 16-bit extensions. For
> >> example it can combine six 8-bit registers into three 16-bit registers,
> >> and do some simple arithmetic on them (add/sub). This may not sound
> >> impressive, but it is way easier to program than a pure 8-bit CPU like
> >> the 6502/6510 which doesn't know of 16-bit at all.
> >
> > There are registers other than BC DE and HL which behave as 16bit
> > "register-pairs", not least of all the index registers IX and IY, there
> > are also shadow registers and 16bit memory accessing instructions to
> > consider above and beyond a 'pure' 8bit machine.
>
>EXX ;-)
>
>But I wouldn't call these shadow registers very useful, as you can only
>exchange them all at once with the other set of registers. And of course
>there are the index registers, but they require rediculous lengthy
>opcodes especially in combination with the CBh and EDh opcode "modifiers".
>
>BTW offtopic: I would have been very happy if the 68000-series had
>become the industry-standard instead of i386, it has one of the neatest
>sets of opcodes I have ever seen (and used), it's almost like you're
>programming in C.
>

There are many uses for EXX, interrupts is probably the most
pronounced, but anywhere that two operations are occurring concurrently.

And Yes, 68K is/was beautiful :)

BC
Received on 2007-08-18


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