Spectrum Computing

PANDEMIA . Fake perspective - that what exactly describes by feel of that screen. I think it is one-point perspective (see wiki) because all furniture lines should end in one point far away. "All objects will recede to points in the distance". https://en.wikipedia.org/wiki/Perspective_(gr...

Lethargeek wrote: ↑Sat Mar 09, 2024 2:40 pm and the entire scene is not

Well it sort of is. There is no perspective (you can see the tiles on the walls are all parallel lines). It's just a really weird mash up of two oblique angles.

They're all oblique projections, since none of them apply perspective. There's always a possibility with this that the end result can "look odd" because your brain can interpret the image in multiple ways and none of them are entirely correct.

One thing to bear in mind is that, unlike the Amiga, you're don't really have to worry about someone having a faster CPU. So a lot of the time HALT on it's own will suffice. If you're execution time per frame is very variable, I'd personally probably use my own interrupt routine rather than the ROM ...

@AndyC But sprites in Enduro are much bigger and active screen area is also much bigger. I think the Enduro engine is just more advanced. Outrun effectively has to calculate and render two roads all the time (it's how branching and highways work), which requires significantly more maths than the si...

toot_toot wrote: ↑Tue Mar 05, 2024 7:08 pm It does make you think there’s a fundamental bug somewhere in Outrun that’s slowing things down.

Outrun has more features like multiple roads/branching etc. All of which makes things slower.

The timer is probably just counting every X game frames, it's less accurate but fairer on a player since they don't get penalised for game slowdown that way. I can't off hand think of a reason the game would run slower on a 128, especially not the 48K version. Unless it's still using the ROM interru...

ZXDunny wrote: ↑Tue Mar 05, 2024 1:24 pm Yeah but the BASIC can and well... it did, y'know? With a single OUT.

Which is why I followed it with a paragraph about what probably happened....

XoRRoX wrote: ↑Tue Mar 05, 2024 12:51 pm As using the AY chip isn't as CPU-hungry as the beeper, I'm wondering if the 128k version plays faster.

Yeah, I would expect so unless it still has beeper FX (I can't remember off hand).

When playing around with these things, RAM is usually mostly zero. And zero is NOP, so a jump almost anywhere has a high chance of hitting empty space and just running into the data structures up near RAMTOP. I'd hazard a guess that interpreting that as code leads to the sequence of instructions tha...

equinox wrote: ↑Tue Mar 05, 2024 11:19 am What was the chance that you would fail to get through Skylab Landing Bay?

105%, approximately.

The point is that it can *run*/execute something, and not merely do a beep or border. Maybe it is a consequence but you did say this was totally impossible. 'sall. I said the hardware can't trigger something like that from a single OUT, but changing a paging register probably causes the machine to ...

Let's try to ignore Icon Graphix ... Wait. Was that the one they gave away on an SU covertape at some point? The one where you had to play a music tape in the tape deck while you were using it or the keyboard routines didn't work correctly? Aside from that glaring bug, I seem to recall it wasn't ac...

ANDY APOLOGISE I stand by what I said. The OUT doesn't really do all the things you're seeing, it's just a consequence of what follows. The OUT swaps the paging arrangement to some unexpected configuration. At that point one of maybe four things could suddenly be true: 1) One of the other 128K ROMs...

Given that it has 50% more of both 'Great Utilities' and 'Adventure Games' than 'Arcade Games', I'm guessing it's an early PD library trying to vaguely disguise the fact that you're buying into a giant Cassette 50 scheme without the calculator watch or quality control, rather than a lending library...

1. Gilligan's Gold
2. Commando
3. Ghosts and Goblins

I would have thought that any game that uses a backbuffer that is fully redrawn each gameloop on 128K would use that since it avoids having to copy the backbuffer to the screen? You'd think that, but it often wasn't the case. Probably a lot of developers had routines built for the 48K, which often ...

An emulator that can set a breakpoint on bit D3 of I/O address 7FFDh could be used to confirm it. Whether it's "interesting" enough for anyone to spend time investigating is another question I guess.

There's really two different situations, which can heavily influence the answer: A game that runs on both 48 and 128 machines. This probably accounts for the vast majority. Because you wouldn't want the game to break on 48k, you're limited in how you much you can really add. Commonly using the extra...

Not sure I agree. Consider Manic Miner: perhaps it could've run faster on some screens, or slower on others. Who knows? But would that have been desireable? For me, that's a resounding no. So far as I recall, Manic Miner's speed was its speed, screen through screen. I think in terms of 'experience ...

Yeah, there's no reason it couldn't run more like HoH. Dunno about frame rate locking, that's good in action games but when you're already running at pretty low frame rates it might not be entirely desirable.

On the Beeb you have that strange double-cursor mechanism where you have to LIST the desired line, cursor your way up there, and then hold down a special Copy key to re-enter it (or just the parts you want to keep). The Amstrad CPC (as far as I recall) involves entering EDIT 100 and then line 100 p...

Firstly, there's no way a single OUT could do something like that on its own. The hardware just doesn't work that way. But you do remember it, so why? Probably what's happened is you've caused the paging hardware to switch something that the system isn't expecting. So suddenly changed what ROM is ac...

Not too drunk then yet ;) It's not self modifying that code in that function though so there's no need to repeatedly write it back to 34680. Unless they do that just to waste some T states so that the OUT instructions occur at some multiple of 8T (which is apparently a thing you should do, I know n...

49157 looks like it may be an entry point (strange to do a JP at the entry point though - so I suspect it might be data or a variables there instead). A common thing amongst AY players (at least back in the day) was to have three entry points right at the start - one to initialize the routine, one ...