Spectrum Computing

What's the most efficient way of scrolling the attribute memory sideways, right to left, introducing a column of, say, black ink/white paper attributes down the right hand side? In C, which is where I'd start, it's a fairly simple loop of 31 byte copies from an attribute address into the byte one ad...

Ast A. Moore wrote: ↑Thu Jan 04, 2018 8:03 pm Neat. I seem to remember a similar trick with a line of scrolling text made out of screen attributes. Was pretty jaw-dropping the first time I saw it.

Yeah, I saw that too! In fact, that's what I intend to try next!

And on that topic I need a new thread...

Here's the result of my aforementioned dicking around: [youtube]https://youtu.be/DW1viKMx5T0[/youtube] I think you'll all agree that's dead useful! :D The interrupt routine which animates the coin is written in C, using z88dk. It currently needs a tweaked z88dk runtime library because the default on...

I think the library routines are overcomplicating things (well I can't follow what's going on!). Completely agree! Chucking everything in there along with the kitchen sink just seemed to make a mess. I lost track of the project and what was being learned along the way ages ago. Go back to basics. W...

But why is IY needed to point to the ERR NR system variable and why doesn't it appear to be dereferenced in the Spectrum ROM? A lot of (but not all) system variables are accessed via the IY register in ROM. That’s just how it is. IY is initialized by NEW and STACK_BC routines. OK, so my puzzlement ...

I was dicking about with an IM2 interrupt in C using z88dk. I wanted to return to BASIC leaving my interrupt routine running, but z88dk doesn't support that. (It restores IM1 when returning to BASIC from C.) It's a simple-ish change to add support to the framework, but I discovered I really didn't u...

I don't think a whole lot of Spectrum software was written with what might be termed modern practises which simplify the porting effort. Modern games use abstraction and internally layered APIs to provide services such as video, sounds and I/O. You rewrite those layers, keep the API the same, and th...

Nomad wrote: ↑Tue Jan 02, 2018 9:04 am The use case is - guy pays 5 pounds and is instantly disappointed but not enough to demand a refund.

ROFLMAO!

Keep going, and keep commentating. I love threads like this.

[mention]PeterJ[/mention], did you get any further with SP1? I've been looking at it for a few hours now and all I'm getting is bl**dy frustrated! I was trying to write a simple program which would print a single sprite on the screen. Working forwards (i.e. starting with a blank editor) I just hit c...

Vast improvement.

I need to look at the code more carefully, but the graphical content is immediately understandable.

I cringe at my ignorance as I type this, but hey, I never had a 128K, and had moved on to 16 bit machines long before it came out. I was looking at the specs of the 128K Spectrum and noted what appears to be banked screen memory. There are 8 16K banks which can occupy the range 0xC000 to 0xFFFF, and...

Having thought about it a bit more, what you could do is split it into 2 lessons. The first could use a sprite one pixel high, which would allow the focus to remain solely on how the horizontal preshifting works. Then make the second lesson add the other 15 rows of the sprite, which is what you have...

Use a hollow box graphic, not a filled one. That black smear going down your first image isn't at all clear. Maybe add a grid on 8 pixel boundaries so it's clearer that there's 3 bytes of width, not 2. It took me a while to work out why the bottom block of the graphic has a white line down the right...

Yeah, I know. :) I think the difference is that, unlike yourself and many others, I don't own a real Spectrum, and hadn't typed on a rubber keyboard for over 30 years. The first thing I did with the RZXS keyboard was type "BEEP 1,0", and the way the muscle memory from my teens kicked in to...

Good review of the RZXS, but it's a pity he focuses solely on compatibility of games. He doesn't even mention how it works (and feels) for typing in BASIC programs or assembly language. The retro experience is more than just games, IMHO. Not that I want to knock The Spectrum Show. It's always great ...

Well, not quite. Your hitting Continue has nothing to do with screen updates per se. What does is the interrupt timing (as on a real machine). So if you continue stepping through your code long enough for an interrupt to trigger, the screen will update. Oh, I see. Yes, that's clearly how it should ...

I use Linux, and Fuse is my emulator of choice. Its debugger isn't great, however, and has a significant issue which bugs me: if I single step code which writes into screen memory, Fuse doesn't update the main display window. It's not until you click the Continue button that the display updates. Wha...

What did it do, exactly?

Merry Christmas to all! Peter, how about putting up a page with a list of things that you'd like done? I have technical skills, and some writing ability, but not a great deal of spare time. I'd volunteer for the odd job now and then but I really don't know what you need or how much commitment it wou...

PeterJ wrote: ↑Fri Nov 24, 2017 7:16 am This really is a fantastic piece of work. Thank you.

Thank you! It's my only contribution to the Speccy scene so I'm grateful for the appreciation.

If you press "1", the keyboard will say you pressed "A". If you press "A", the keyboard will say you pressed "O". If you press "Z", it will say you pressed "<". It works, but it's a hack! :) If you press "1", the keyboard will ge...

This keyboard can report key presses only. It cannot report key releases. Therefore in normal "QWERTY Mode", a game would know when you pressed a key to go down, but it wouldn't know when you stopped pressing it. The other "Game Mode" is a hack. For instance, whenever you press ...

Assuming by "basic mode" you mean the standard PC keyboard mode, yes, it's redundant IMHO. Much as we all love our 40 rubber keys, it's not really an adequate keyboard for a modern PC. Mine sits connected to the PC via USB cable, permanently in the, er, "other" mode which works ...

I'm not sure what you mean by "basic mode". Flick the switch on the back of the RZXS and set the RZXS flag in the Fuse config, then it works perfectly as a fully fledged Spectrum. I was going to suggest the same. In fact the basic mode seems to be somewhat redundant as a mode anyway doesn...

The main issue however is that the keyboard doesn't really function when used in basic mode, the key commands don't match up and so it's no use as a fully fledged Spectrum, games tend to be fine however. I'm not sure what you mean by "basic mode". Flick the switch on the back of the RZXS ...