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Yeah actually I'd love to know where Crazy Balloon came from originally. Someone must know.

(Maybe Dave M knows where he got the original disk image from? Eventually these things have to trace back to their source!)

Coeus wrote: ↑

Fri Oct 05, 2018 11:40 am

To have got as far as producing a masked ROM and for it then to be rare in the wild suggests a serious bug. Any idea what is was?

The cassette one which corrupted saved files (which required a dummy byte in the leader tone)? Or was that a 0.10 bug fixed by 1.00?

"This is some text" would appear at graphics co-ordinates 100,100 and "This is some more text" would appear at text co-ordinates 4,5. In other words even while VDU 5 is in effect I would expect VDU codes that are documented as moving the text cursor to do exactly that but then when printable charac...

It's definitely very curious. It'd be interesting to know what the rationale for removing it was, because, as you say, it was a breaking change from 0.10 to 1.00, and it doesn't really seem like a bad feature. My thoughts are: * For clarity: it's easier to state that TAB(x,y) is for the text cursor ...

"This command has now been implemented" sounds to me like something which was proactively done, as opposed to "this behaviour changed" which sounds like documenting something which may or may not have occurred by accident. That was my take anyway. Possibly we're looking at this from two different pe...

The Oric has weird clock requirements as the ULA requires 2 RAM accesses for every CPU RAM access (it has to read a bye from video memory, and then look up its pixel definition, Teletext-style).

Aha! http://chrisacorns.computinghistory.org.uk/docs/Acorn/AN/036.pdf Support Group Application Note 36 Master 128 Welcome Disc "Converter" Program l) On OS 1.20, the TAB(X,Y) vdu sequence has no effect while in VDU 5 mode. On the Master Series this command has now been implemented in this mode, to ...

I do not believe that is correct. In every OS version I've tried, and in RISC OS, Brandy, BB4W and BBCSDL, VDU 5,30 moves the graphics cursor to the top left, not the bottom left, of the graphics viewport. Yes, my apologies, you're right (just tried in jsbeeb). I guess I was remembering the fact th...

Comparing disassemblies, OS 1.20 does this: ;0322 = supplied X coordinate ;0323 = supplied Y coordinate C787 JSR &C588 ;A=0 if text cursor A=&20 if graphics cursor C78A BNE &C758 ;exit C78C JSR &C7A8 ;exchange text column/line with workspace 0328/9 C78F CLC ;clear carry C790 LDA &0322 ;get X coordin...

This observation was made by Richard Toohey here , when looking at OS 0.1 games which didn't run on OS 1.20. It was the first time I'd heard about it. The OS 1.20 approach feels like the right one, but I'd assume it was a deliberate choice to reinstate the old behaviour in the Master OS (as it would...

The early Acornsoft disk protection systems used undocumented opcodes, as does Zalaga. The tape protection on Nightshade and Lunar Jetman won't work because of the timing difference for JMP (indirect). I can't think of any other issues for the moment though.

The hostility of some of the RISC OS community is one of the reasons I turned my back on it. Sorry that you had to get involved in that

Citadel uses a reduced height screen, using just the last 20 or so rows of a standard MODE 2 screen, and is then recentred vertically. So I think what you have there looks correct!

The problem with these formats is that they are literally just a sector dump with no metadata or versioning, or anything which can readily help to identify their validity. In fact the extension is the only thing which really identifies them at all, and the only thing which can distinguish a single s...

Superb! Looking forward to playing with this!

I think the Beeb 'suffered' this more than most other platforms though, because BBC BASIC was so much faster and better than BASICs on other machines. I'd be incredibly surprised, for example, to find commercial games written in BASIC on the Spectrum beyond the first few months of its release, becau...

Way too young I think, I've tried a few on linkedin, but I think since we are talking mid 60's onwards, age wise, they could be well retired :) Ah I forgot to mention, age wise I think it could be mid 60's onwards. Ah... I figured that the chap I came across finished university in 1984, which was m...

Plankwalk


All Basic apart from the monster logic. And it unironically remains one of my favourite games on the Beeb to this day!

Long shot, but... https://www.linkedin.com/in/steve-sutton-10236320 ? Name, age and location seem to coincide, but I suspect it's coincidence. The QL work would've had to be as a side-project rather than a full-time job. Edit: His first listed job includes "Large Civil & Defense Systems, Banking, Go...

A final word of caution. If you're doing this from BASIC, ensure that the program line is located below &3000 in memory, otherwise the *FX108,1 will page out the BASIC program!

What is this witchcraft!!! So you mean that only every other scanline gets an hsync? I'd never have expected that to work, but how cool that it does! I guess composite needs the colour burst and whatever at the beginning of each line, and without it bad things happen. What happens if you turn on int...

B-Em can be coaxed into displaying it in the same way as jsbeeb by selecting Settings -> Video -> Display type -> Interlaced. It's really hard to know how to display a 50Hz emulated screen on a PC with an arbitrary monitor refresh rate. If you don't mind the latency, you can run a frame in advance a...

That would require a vertical rupture type technique, but I'm uncertain whether that even works in interlaced modes; it depends whether the crtc uses R4 or R7 to determine when to toggle the field type. It would work if it were the latter.

It can if you toggle between each screen bank on each field. I remember the Acorn User article, on my monitor it flickered unacceptably. I'll see if I can find it. Yeah, I guess if you get the timing perfect, and switch displayed bank just before line 128 is rasterised, you could do it. You'd have ...

And the interlaced sync and video mode can be used to ensure the even field reads even addresses, and the odd field (which is offset by half a scanline) reads odd addresses, thus avoiding the problem with the fields being out of sync with the rendering. The only problem is you have to use the Beeb's...

And of course Repton 1 & 2 got a release as Repton Mania on the Spectrum later on. By Fair Means or Foul got a simultaneous release on multiple platforms, but it's probably safe to state that it originated on the Beeb, it being a Superior Software production. I think The Sentinel and Cholo were also...

Thrust also started life on the Beeb, and was then ported to C64, CPC, Atari and Speccy while they worked on an Electron version. The C64 version was then released before the Beeb/Electron versions.

Thanks for checking it out Dave. It's nice to have this confirmed (according to that jsbeeb github thread, I already had a hunch about it a couple of years ago). Not sure how you're arriving at minimum 1 cycle latency for interrupts, but we can continue that discussion on 6502.org!

I'm going to stick my neck out and claim that CMOS 6502 don't have the special interrupt behaviour on branches. Here's the jsbeeb change I was alluding to earlier: https://github.com/mattgodbolt/jsbeeb/commit/f65a02d1677ba42ddddb50fd7847a6549a0bb5c8 and the bug thread about it: https://github.com/ma...

I think this example is more like the one in the trace (with respect to the IRQ signal timing): http://visual6502.org/JSSim/expert.html?graphics=false&steps=33&r=fd&a=fd&d=58a900f000a95ceaea&irq0=11&logmore=sync,irq,480,D1x1 I've added signal 480, which is derived from the irq signal in the previous...