Re: OT (FAO Ian Oliver and any speccy programmers)

["Jason Lee" <jasonjlee@xxxxxxx>]

wow, I remember carrier command on the amiga..

great game..never did manage to beat it.. wasn't there a writeup on it in
edge a few months back..(I just checked issue 95) I love those articles...

I had a spectrum 16K as my first machine, (Still have my kempston
joystick!)
and I remember starstike, that was a great game too.

I still remember seeing the first 3d wireframe stuff on the speccy and
thinking WTF..

Ian, I know this is wildly off topic, but I've had a little programming
thing bugging me for the last year, its easy I promise...

I remember the spectrum screen memory layout was something like this..

The screen was split into three.  Each third worked as follows...

Each byte controlled one 8 pixel row. After each complete row of pixels
across the entire screen the next row was the top of the next set of
character blocks ...

a Mem1 ---------------------- mem x
b
c
d
e
f
g
h
i Mem x+1                             mem 2x

anyway... forgive the refresh, i'm just checking that i'm right.

The question is, How is it possible to smooth scroll a spectrum screen....?

I wrote a routine, back when I was at school, but I'm not sure if....

1.. It was running to fast or slow, or it wasn't tied to screen refresh I
can't remember if there was a Vertical blank interrupt on that machine?

2. It was running to slow, cause it didn't use any of the clever tricks of
moving the stack and pushing lots of registers which I learned latter on
68000..(Memory clearing trick I seem to remember..) I think it was the most
striaght forward code you could write in assembly.

So was there a trick? Its just kinda always bugged me that I've never found
out what was wrong.

I progressed to a c64 about the time of Thing on a Spring, so I got into
6502 not long after that, and I never did get back to that code. Hardware
sprites and scrolling were much easier..

Regards
Jason

----- Original Message -----
From: "Ian Oliver" <ioliver.lists@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Friday, August 10, 2001 9:48 PM
Subject: Re: [ukha_d] Dreamcast MP3 player


> In article <IDEHIDLMLEPHMHEGEHICGENGCIAA.Mark@xxxxxxx>,
Mark
> McCall wrote:
> > Ah...remember this on my Atari STe.  You jumped from controlling
planes
to
> > tanks etc.
>
> I hope you *bought* a copy.  :-)
>
> Regards
>
> Ian Oliver
> Sunny Leeds, UK
> Using Java on Tini for control via Dallas 1-wire
>
>
>
>
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