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On this subject, I noticed that B-Em has a small bug in that you get uneven vsync periods if you change the active edge of the CA1 interrupt to be positive instead of negative. The video emulation should really wait half a scanline on even fields in interlace mode before putting CA1 high. Interlace ...

Yeah Revs was one of those well-known games which really tested emulator accuracy in the early days (along with Firetrack, Uridium and Snapper). Get it wrong and all the raster fringes will move slowly up or down the screen. Definitely sounds like some kind of timing is broken. Maybe interlace? I th...

In the past I've tried to contrive that bit 1 of &258 is set, so BREAK does a memory clear reset, and that &287 contains anything but &4C so it doesn't appear as a BREAK intercept. I don't think there's anything you can do about NMIs though - if there's any device hooked up which can generate them, ...

And of course Mayhem in Monsterland, provided your machine can handle the VSP technique used for the scrolling without it crashing!

Yeah - the best way to force a reset is:

I believe a memory clear reset (*fx 200,2) is somewhat distinct from a power-on reset too, though I couldn't tell you exactly how.

Nice video on Exile.

https://www.youtube.com/watch?v=IhsFq9ZBJds

Ah, I see! You filled in the gaps I was missing, namely the use of R3, and the double buffering!

Still have to contemplate that write-up a little longer before it properly sinks in though.

It's a great little demo - never seen game scrolling like that on the Beeb before!

You should take out the bitcoin mining code too!

Yesterday, I thought that I would revisit MODE 1 single pixel horizontal scrolling for games and this morning I have a nearly working timing test. In this diagram, I am trying to show how the new pixels are added to the existing image. https://stardot.org.uk/forums/download/file.php?id=45687 how th...

Here's a spectrum analysis of the real one and ElectrEm's, for comparison: Real real.png ElectrEm electrem.png Both dominant in odd harmonics, as per a pure square wave, but the real one is somehow more filtered. Not sure why the even harmonics in ElectrEm's waveform are so dominant, when it looks s...

Whilst that may well be true, it's perhaps worth noting that the waveform being very different doesn't imply that the sound will be different. For example these two waveforms should sound identical, because they differ only in the phase of the harmonics, and the ear isn't sensitive to phase: Yes! T...

Yeah, totally agree with that. From the very start, you really feel "on your own". You've got no weapon, no map, and not really any idea what to do. The lack of on-screen text or any kind of HUD further adds to the feeling of total isolation, and creates a totally immersive experience. In other vers...

Bah, you beat me to it!

It worked for me! And it was so familiar yet so elusive. And then when I was least expecting it, the answer popped into my head: <spoiler> Acornsoft Monsters </spoiler> That PLAY command line is pretty versatile! Great to be able to write a little tune like that in such a small number of characters.

This is from one of those single screen platformers from the mid 80s! Was going to guess Karl's Kavern but I couldn't see it on the attract screen. Nor does it seem to be Blagger. Hmmmm

I typed in the whole of Codename Druid back in the day. Like you say, the big hex listing was the horror at the end - I can't remember how many days (weeks) it took. In the end, I was never sure if I'd typed it in exactly right, as the druid had a habit of sometimes leaving trails from the end of hi...

sa_scott wrote: ↑

Mon Apr 01, 2019 3:24 pm

Ah, that's clever. Didn't know we had a linkbot for stuff like this. Thanks!

Nah, it was just me. I'm trying out a new career direction

BBC Games Linkbot v1.0


Runemaker - Codename: Druid


Block Breaker


3D Asteroids

Not sure how much of the BBC OS API you support, but OSBYTE 25 is the way to reset characters to their default definitions. I feel that this should just happen automatically when returning to the BASIC command prompt (i.e. on an implicit or explicit END, or an untrapped error).

Hard to say. I don't think anyone ever used those PLOT codes, ever, in the history of the Beeb

Interestingly, the AUG nails it.

Appendix E - Plot Number Summary

8-15 Last point in line omitted when 'inverted' plotting used

...which is exactly the implemented behaviour in OS 1.20.

Assuming, as you say, that the reason for providing it at all was so that chains of lines plotted in EOR mode would not have their joining points EOR'd away, the approach taken by OS 1.20 was quick and easy, and correct for its main use case, but not really correct overall. The change in the Master ...

Fairly sure my old school got rid of all its Beebs from the computer room and replaced them with RM Nimbuses around 1992 - I don't remember there being any Beebs when I did Computer Science A level around then. There were a couple of A3000s sat discreetly at the back of the room though, mostly used ...

Can't think of any examples like the Harry S Price Speccy ones though, where someone just ripped off entire pieces of others' games and passed them off as his own. I'm not even convinced Star Clash was guilty of stealing code from Elite. Always struck me as a double standard that Acornsoft brought a...

There were loads! Just Acornsoft alone came out with Snapper (Pacman), Planetoid (Defender), Meteors (Asteroids), Monsters (Space Panic) and Arcadians (Galaxians), Carousel (Carnival), Hopper (Frogger). Then there was Zalaga (Galaga), Deathstar (Sinistar), Skirmish (Joust), a bunch of Q-bert clones,...

I'm taking tentative steps into putting together a very simple demo along these lines - first step is a tool which can extract maps from Doom wads and convert them to a simpler portal format. (For the technically minded amongst you, this involves having to decompose an arbitrary polygon with holes i...

Come on this must be doable?! Surely hee hee. A little mockup screen....... :wink: :D https://i.imgur.com/4YlvQCh.png I have to say, that is very inspiring. And your eye for the technical as well as the aesthetic is superb (I noticed the exactly 128 pixel wide playing area!). When considering Doom ...

Incidentally this lack of bass tones on the Beeb is one of the reasons that a lot of music lacks so much depth on it. I worked around the limitation in the past by modulating a very high frequency tone on and off according to a VIA timer, but it's a shame to have to do that. And using periodic noise...

The lowest tone you can out of the SN chip at the speed it's clocked at on the Beeb is 122Hz, which corresponds roughly to the B an octave (and a bit) below middle C. So looking at that diagram in the User Guide, I would say Middle C actually does correspond to pitch 53 in the SOUND command.