🚀 go-pugleaf

David Kastrup <David.Kastrup@t-online.de> wrote:

> real-address-in-sig@flur.bltigibbet (Rowland McDonnell) writes:
> 
> > Giuseppe Bilotta <oblomov@freemail.it> wrote:
> > 
> > > Robert Myers wrote:
> > > > 
> > > > A processor that requires special code to get decent
> > > > performance is not especially attractive, and if the P4 weren't an Intel
> > > > product, no one would be using it.
> > > 
> > > Well, Intel CPUs have always suffered from bad design problems which
> > > require hoop-jumping, contorsionism and loop unrolling to get decent
> > > performance.
> > 
> > Back in the days of the 4040, this wasn't considered a problem.
> 
> 4040?  We aren't by chance confusing this with the 4004? 

Highly likely.  It might well be 10.19am BST but I've only just finished
a bottle of wine (up all night, y'see - I might even hit the sack
soonish).

(and `we'?  I might be mad, but I've never attempted multiple
personality disorder ;-) )

> And the
> 8080 still was a rather clean design.  The Z80, in constrast, was
> convenient but awful: the price you paid for some of its features was
> prohibitively high.

Hmm...  Maybe, maybe - but was there anything missing from the Z80
compared to the 8080?  (I never did use an 8080 myself, and I don't
recall doing any machine code[1] programming of a Z80 beyond the age of
about 14 - draw your own conclusions...)

> For example, one popular way to clear out a memory area was do store
> a 0 into its first position, then use the LDIR instruction to fill
> the rest.  21 cycles per byte.  Unroll to LDI, get 16 cycles.
> 
> Of course, the fast wa was to place the stack pointer at the end of
> the area, and do repeated PUSH HL.  11 cycles for _two_ bytes.

Interesting - ta.

Rowland.

[1]  Yes, really - I had no assembler.

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