Search found 1260 matches

by Rich Talbot-Watkins
Thu Jun 21, 2018 9:31 am
Forum: software: new games
Topic: New version of Scramble for the beeb (going well)
Replies: 47
Views: 2609

Re: New version of Scramble for the beeb (going well)

It's amazing to think how we did it back then: armed with just BBC BASIC with its built-in assembler, its clunky line editing, and ingenious ways of working around the memory limits. Matt and I did the first version of Blurp and a few other things like that, although we'd written a ROM which gave us...
by Rich Talbot-Watkins
Mon Jun 18, 2018 4:49 pm
Forum: stardot.org.uk
Topic: Post editing
Replies: 59
Views: 686

Re: Post editing

Another possibility is only allowing time-limited editing, apart from the first post of a topic, via this extension: https://www.phpbb.com/customise/db/extension/gn36_firstpostedit If you've already read a post, it's easy to miss any subsequent edits to it, so this doesn't seem like a bad idea to me...
by Rich Talbot-Watkins
Mon Jun 18, 2018 1:17 pm
Forum: stardot.org.uk
Topic: Post editing
Replies: 59
Views: 686

Re: Post editing

I have had a look over lunch, it does seem fairly easy to make a forum theme based on the current one that omits the edited message footer unless someone puts something in the reason box. If this sounds like it would mitigate most concerns then I'll put that into play this evening - it will require...
by Rich Talbot-Watkins
Mon Jun 18, 2018 7:55 am
Forum: stardot.org.uk
Topic: Post editing
Replies: 59
Views: 686

Re: Post editing

A good while back, I think the forum used to report all edits, and then this disappeared with one of the big upgrades. Since then, if I edit one of my own posts to add additional content or correct issues, I nearly always prefix it with 'Edit:' myself to make it clear that it's been added. I think t...
by Rich Talbot-Watkins
Tue Jun 12, 2018 3:38 pm
Forum: software: classic games
Topic: Acornsoft Labyrinth
Replies: 10
Views: 284

Re: Acornsoft Labyrinth

Cheers for the answer. However it looks a bit complicated for me. I am using a SD collection of games so looks like I need that specific drive with the game and load it manually? I do use special menu otherwise http://joxi.ru/v29Xeq1i3pY95m Yes - mount the disk image which contains Labyrinth and tr...
by Rich Talbot-Watkins
Tue Jun 12, 2018 3:36 pm
Forum: software: classic games
Topic: Acornsoft Labyrinth
Replies: 10
Views: 284

Re: Acornsoft Labyrinth

Any idea why that was done? :?: Maybe they thought it gave the graphics a strange swirly ethereal quality (which it certainly did on my TV) and thought it fitted the game. Or more likely it was just a mistake. It also has the effect of lowering the frame rate to 49.3fps but I doubt they did it to w...
by Rich Talbot-Watkins
Tue Jun 12, 2018 1:49 pm
Forum: software: classic games
Topic: Acornsoft Labyrinth
Replies: 10
Views: 284

Re: Acornsoft Labyrinth

Found it! This works on the Acornsoft release on the STH site - haven't tested any other versions.

Code: Select all

*LOAD LABRNTH
?&18D1=127
CALL&5D00
by Rich Talbot-Watkins
Tue Jun 12, 2018 1:39 pm
Forum: software: classic games
Topic: Acornsoft Labyrinth
Replies: 10
Views: 284

Re: Acornsoft Labyrinth

Yeah Labyrinth programs the video controller with non-standard values, specifically the horizontal timing is too long for a PAL display. My TV even used to have some small problems with it back in the day. It'll be easy enough to patch I suspect, but it'll need someone to find where CRTC R0 is writt...
by Rich Talbot-Watkins
Tue Jun 12, 2018 8:35 am
Forum: software: other
Topic: Any short type-ins for unattended Beebs?
Replies: 75
Views: 3185

Re: Any short type-ins for unattended Beebs?

timmy wrote:
Thu May 24, 2018 8:52 am
My school favourite was to do a quick:

Code: Select all

?&FE40=0:CLS
on all the machines before the teacher came and then sit down and wait for people to start typing...
What does that do? Enables sound chip writes at the same time as keyboard scan? It doesn't work on jsbeeb or B-Em... I wonder why? :-k
by Rich Talbot-Watkins
Fri Jun 08, 2018 3:10 pm
Forum: projects
Topic: 640x512 50 fps Bad Apple on a B... how?!
Replies: 28
Views: 822

Re: 640x512 50 fps Bad Apple on a B... how?!

Amazing the technology you can get these days.

Image
by Rich Talbot-Watkins
Fri Jun 08, 2018 1:25 pm
Forum: off-topic
Topic: Microsoft to buy Github
Replies: 30
Views: 530

Re: Microsoft to buy Github

I fully expect GitHub to end up with adverts everywhere though :( The annoying animating type that ended up all over Skype and MSN Messenger before it.
by Rich Talbot-Watkins
Thu Jun 07, 2018 7:10 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

A counter which is preloaded and counts down to zero is very much preferable - but the block diagram doesn't indicate that.) And indeed we know it not to be the case, as it's possible to change registers during the CRTC frame, and their new value will be correctly used as the upper bound. Are there...
by Rich Talbot-Watkins
Thu Jun 07, 2018 7:03 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

Just pondering this again this morning. I think, in terms of simplicity, everything makes sense apart from one thing. Are we sure that R12/13 take effect when set in the final scanline of the previous frame? Kieran, do you have concrete evidence of this working OK in your demo, or is there a chance ...
by Rich Talbot-Watkins
Wed Jun 06, 2018 10:58 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

This does make sense. Looking at the b-em source code it's doing approximately the following: IF HorizontalCharacterCount==R0 AND ScanlineCount==R9 AND VerticalCharacterCount==R4 THEN VerticalCharacterCount=0; FrameCount++ Presumably jsbeeb similar? What do we think that logic should look like? Bot...
by Rich Talbot-Watkins
Wed Jun 06, 2018 10:54 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

The easiest (and hence cheapest) counters have unsynchronised outputs. That is, propagation delay of the logic circuits causes the count to ripple through each stage, with the output of each stage changing one after another. This results in the output having invalid data for brief time periods. The...
by Rich Talbot-Watkins
Wed Jun 06, 2018 10:13 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

1024MAK wrote:
Wed Jun 06, 2018 9:35 am
Here is a diagram of a 74LS688 comparator from a TI datasheet:
Happy I guessed that right, at least :lol: Even if I didn't realise it would invert the inputs (or indeed the output!).
by Rich Talbot-Watkins
Wed Jun 06, 2018 10:00 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

There are some curious things I haven't yet figured. For example, the Scanline Counter has as its MC input: SLC==R9 OR (something from the Linear Address Generator). What can that be doing? Also interesting to note that the Linear Address Generator gets Hend as an input - this is so that it can cac...
by Rich Talbot-Watkins
Wed Jun 06, 2018 9:52 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

Looks like my interpretation of MC is wrong - thanks Mark. So MC will perform an immediate reset then. (Edit: although here 's an example of the sort of circuit I was imagining: a synchronous counter with a synchronous reset.) By the way, I think CC on the diagram is just another CO that's scanned b...
by Rich Talbot-Watkins
Wed Jun 06, 2018 9:48 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

Edit: Mark just posted a load of great stuff, but going to post what I had here anyway, in reply to Ed! That sounds more complicated Ed! I assume a comparator is no more than a bunch of ANDed XNORs which surely can't have a prohibitively high transistor count. My mental model for this is as follows:...
by Rich Talbot-Watkins
Wed Jun 06, 2018 8:39 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

That all sounds very plausible, Kieran! It makes sense once you realise that the timer itself will trigger a scanline early; it also helps to explain why the first scanline was apparently displaying OK when, by the same account, you'd expect setting R4=0 during the first visible scanline to be ignor...
by Rich Talbot-Watkins
Tue Jun 05, 2018 11:24 am
Forum: emulators
Topic: Video Timing
Replies: 58
Views: 1819

Re: Video Timing

With the diversion on restoring 'normal' CRTC conditions, I think I've lost the discussion here! Kieran, can you explain again what problems you're seeing now on real hardware, compared to emulation? During the demo (and also during the transition)? Just to make sure I understand your code well enou...
by Rich Talbot-Watkins
Mon Jun 04, 2018 9:29 am
Forum: software: new games
Topic: New version of Scramble for the beeb (going well)
Replies: 47
Views: 2609

Re: New version of Scramble for the beeb (going well)

Yeah, that was my take on it as well (the "race conditions" I speculated about above). I wouldn't be surprised if every register which holds "value minus 1" is matched to the internal counter early, and the results latched until the following time round. But it still doesn't quite explain some other...
by Rich Talbot-Watkins
Sat Jun 02, 2018 9:06 am
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 107
Views: 2617

Re: 12-second Mandelbrot rendering on the BBC Master!

Turning off the ADC converter got about 77px/s. Interestingly, now jsbeeb and b-em are reporting the same times. I think jsbeeb might be skimping on the ADC emulation... Memory fails me now, but I think it's the other way round. We had a timing test where both B-Em and jsbeeb were out compared to r...
by Rich Talbot-Watkins
Fri Jun 01, 2018 9:41 pm
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 107
Views: 2617

Re: 12-second Mandelbrot rendering on the BBC Master!

I think at this stage, the OS interrupt routine is going to be adding noise to the timing results. I'd be inclined to go to 100% assembler, and shut out the OS, so you could use all the zp and have complete control over IRQ handling, but short of that, you could try reducing the OS IRQ footprint. Tr...
by Rich Talbot-Watkins
Wed May 30, 2018 6:38 pm
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 107
Views: 2617

Re: 12-second Mandelbrot rendering on the BBC Master!

@rtw: d'oh! Obvious in hindsight. Sadly, tsb only has zp and abs addressing modes, so I still need an ora (screenptr); sta (screenptr), but that's a nice 15 px/s. Hence my other suggestion to find a way to move the routine (or some of it) into the zp so that the operand of the TSB abs can actually ...
by Rich Talbot-Watkins
Wed May 30, 2018 3:55 pm
Forum: emulators
Topic: Emulator setup to make all ROM area writes use bank 15 SWR
Replies: 23
Views: 395

Re: Emulator setup to make all ROM area writes use bank 15 SWR

1.) JSR &CCB3 - The back end of the CLS code, clearing from &6B00 to &7FFFF. 2.) JSR &E9B6 - Wait for VSYNC ( &240 chainging value ) All to save memory. The quick CLS code saves a lot of memory and wouldn't be easy to patch in. We do have multiple OSs for Master 128 to consider! My patches for the ...
by Rich Talbot-Watkins
Wed May 30, 2018 3:27 pm
Forum: emulators
Topic: Emulator setup to make all ROM area writes use bank 15 SWR
Replies: 23
Views: 395

Re: Emulator setup to make all ROM area writes use bank 15 SWR

Are the various copies of Alien 8, Knight Lore etc. compatible with a Master 128 ( with MOS, not OS1.2 )- has somone patched them up? I have the source now and could probably sort them out. I don't know if the bbcmicro.co.uk or STH archives have patched versions. I remember having to patch pretty m...
by Rich Talbot-Watkins
Wed May 30, 2018 2:48 pm
Forum: emulators
Topic: Emulator setup to make all ROM area writes use bank 15 SWR
Replies: 23
Views: 395

Re: Emulator setup to make all ROM area writes use bank 15 SWR

Thanks Kevin! It all looks so straightforward when you see it like that! :lol: I'm one of your statistics who was beaten by Alien8. I had a double challenge though, because I had to try to make it Master compatible at the same time (armed with an image of OS 1.20 from a school Beeb!). I think the "e...
by Rich Talbot-Watkins
Wed May 30, 2018 12:42 pm
Forum: emulators
Topic: Emulator setup to make all ROM area writes use bank 15 SWR
Replies: 23
Views: 395

Re: Emulator setup to make all ROM area writes use bank 15 SWR

I just tried the tape version of Exile in jsbeeb to see how it loads - definitely one of your trademark decrypters (length &301 ;) ) in ExileL and ExileB! Do you remember why you decided to ditch the custom tape format (one long block) in favour of the standard Acorn format with interblock gaps? I a...
by Rich Talbot-Watkins
Tue May 29, 2018 10:12 pm
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 107
Views: 2617

Re: 12-second Mandelbrot rendering on the BBC Master!

The plot routine offends me; there must be a better way. If you're only plotting pixels onto black (or can contrive colour 0 to mean "unplotted" and colour 8 to mean "black, plotted"), you don't need the AND to mask the screen data. If you had enough zp to put some of that code there, you could rep...