Search found 32 matches

by hexwab
Tue Sep 18, 2018 4:14 am
Forum: programming
Topic: Beeb SOUND weirdness
Replies: 9
Views: 460

Re: Beeb SOUND weirdness

What a peculiar feature! And, as you say, pretty terrible too, if it doesn't scale with the frequency, so that higher notes are detuned more than lower ones. I think that's an OS 1.20 misfire (and they could've saved themselves some space by not doing that as well!). It is terrible, but there is so...
by hexwab
Sat Jul 07, 2018 4:24 pm
Forum: projects
Topic: Twisted Brain Demo
Replies: 38
Views: 3126

Re: Twisted Brain Demo

You can see my own experiments in stable rasters back in this thread from last year https://stardot.org.uk/forums/viewtopic.php?f=53&t=13382 (in which I do give you due credit, doh!) I remember this thread! I remember thinking it should be possible to get better than 10px horizontal resolution. 20p...
by hexwab
Sun Jul 01, 2018 2:57 am
Forum: projects
Topic: Twisted Brain Demo
Replies: 38
Views: 3126

Re: Twisted Brain Demo

6502 newbie here so perhaps this is obvious to everyone else... But can I ask why there are 9 nops but the comments say they take 16 cycles? Wouldn't it be 18? It's 18; the comment is wrong. As to *why* it's 18: much of this code was written empirically. The way I got it working is to make a loop t...
by hexwab
Sat Jun 30, 2018 10:25 pm
Forum: projects
Topic: Twisted Brain Demo
Replies: 38
Views: 3126

Re: Twisted Brain Demo

The vertical sync pulse is the only method we have to synchronise to the entire TV signal. To find the exact cycle of vsync I used the following code taken from the RetroSoftware forum: lda #2 .vsync1 bit &FE4D beq vsync1 \ wait for vsync \now we're within 10 cycles of vsync having hit \delay just ...
by hexwab
Sun Apr 22, 2018 12:30 am
Forum: software: other
Topic: Any short type-ins for unattended Beebs?
Replies: 145
Views: 7817

Re: Any short type-ins for unattended Beebs?

Ooh I like that - sunflower! Cheers. It's based on https://js1k.com/2010-first/demo/779 - interestingly the BASIC version (which I made no attempt to golf) is already smaller than the size-optimized javascript and could probably be easily made half its size. (Basic 4 also has much faster trig, will...
by hexwab
Sat Apr 21, 2018 1:30 pm
Forum: software: other
Topic: Any short type-ins for unattended Beebs?
Replies: 145
Views: 7817

Re: Any short type-ins for unattended Beebs?

Code: Select all

10 MODE 0
20 VDU 23,224,60,255,255,60,0,0,0,0
30 VDU 5,29,640;512;
40 FOR I=1 TO 1000 STEP 2.4
50 D=16*SQRI:MOVE D*COSI,D*SINI:VDU 224
60 NEXT
70 VDU 4
(Interestingly this is about twice as fast on a Master as on a B due to improved VDU 5 handling.)
by hexwab
Mon Jan 22, 2018 11:42 pm
Forum: projects
Topic: New game - tube type thingy
Replies: 53
Views: 4259

Re: New game - tube type thingy

How about checking to see if the 4 pixels you're about to write are the same as what's already there? Not sure how much use this will be over the Tube - I think you meant to say 'if the _host_ is indeed the bottleneck'? If the parasite is the bottleneck then this will surely just make it worse! I s...
by hexwab
Mon Jan 22, 2018 1:43 am
Forum: projects
Topic: New game - tube type thingy
Replies: 53
Views: 4259

Re: New game - tube type thingy

How about checking to see if the 4 pixels you're about to write are the same as what's already there? Currently you have constant 20 cycles for 4*STA abs,X. Doing CMP abs,X ; 4/5 BEQ skip ; 2/3 4*STA abs,X ; 20 .skip and assuming you're crossing a page boundary half the time works out to 26.5 cycles...
by hexwab
Thu Jan 04, 2018 5:28 am
Forum: programming
Topic: 32k memory management for dummies
Replies: 28
Views: 1872

Re: 32k memory management for dummies

Assuming you don't want to disrupt the OS too much, the low-hanging fruit available are: 0400-07FF no gotchas 0900-0AFF cassette buffers, don't go doing any byte-based I/O from tape 0B00-0CFF function key definitions (*KEY) and user-defined characters, don't go using these 1100 onwards should be fre...
by hexwab
Sun Jun 04, 2017 6:11 pm
Forum: emulators
Topic: Games turn off interlace mode
Replies: 21
Views: 2612

Re: Games turn off interlace mode

You can determine odd/even field, by measuring the time between vsync. One field will appear to be one line longer than the other (I forget which one!). If you do this, I think you'll find each field is actually 312.5 lines, or damn close to 20ms. This is because the VSYNC pulse for the odd frame i...
by hexwab
Sat Jun 03, 2017 1:08 pm
Forum: emulators
Topic: Games turn off interlace mode
Replies: 21
Views: 2612

Re: Games turn off interlace mode

To my understanding TVs were always meant to be used with interlaced mode. The FPGA implementation doesn't allow me to discover how it would look like on the real BEEB, but I've seen videos on YouTube of the actual games and they seem fine on the display. So I'm wondering why am I not seeing interl...
by hexwab
Thu May 18, 2017 4:22 am
Forum: projects
Topic: Going great guns on a Prince of Persia port...
Replies: 224
Views: 23690

Re: Starting a Prince of Persia port...

Looking at the CPC version, it's 160x200x4bpp, so an extra 20 pixels horizontally, plus a status line at the bottom. The graphics seem to be stretched from the Apple II version, as the screen layout is identical and yet it takes more horizontal pixels. Hence it's not quite half the resolution (4/7) ...
by hexwab
Mon Apr 17, 2017 4:28 pm
Forum: software: new games
Topic: New Release: Castle Defender
Replies: 32
Views: 6370

Re: New Release: Castle Defender

And completed. This really is a lovely game. I found it a lot less frustrating once I figured out the control scheme. AFAICT, up and down move only between slots with the same X position (with wraparound), whereas left and right cycle through all the slots, by X position first then by Y position. I ...
by hexwab
Sat Apr 15, 2017 8:50 am
Forum: hardware
Topic: Printer port DAC
Replies: 1
Views: 412

Printer port DAC

B-em emulates an 8-bit audio DAC attached to the printer port. How common was such hardware BITD? It was certainly a thing on other platforms . This post suggests that SarahWalker has one (hence its inclusion in b-em?). Anyone else? Tom. PS. Speaking of b-em, I'm not sure what's going on with its em...
by hexwab
Tue Apr 04, 2017 11:35 pm
Forum: projects
Topic: MODE 7 Vertical Rupture
Replies: 31
Views: 2601

Re: MODE 7 Vertical Rupture

Master 128, Cub 1431MS.

Image
by hexwab
Wed Mar 29, 2017 11:55 am
Forum: projects
Topic: Video streaming from ROM
Replies: 2
Views: 691

Re: Video streaming from ROM

SimonSideburns wrote:Neat. You might want to mention the emulator takes a few seconds to start up. (Well, I just did so that should be enough :-) )
It does. It has about 20 megabytes of data to fetch.
by hexwab
Wed Mar 29, 2017 9:05 am
Forum: projects
Topic: Video streaming from ROM
Replies: 2
Views: 691

Video streaming from ROM

Having seen the recent Teletext Bad Apple ( https://bitshifters.github.io/posts/prods/bs-badapple.html ) I got to thinking about what the actual highest streaming video bandwidth that could be achieved on a Beeb is. Answer: frickin' huge bank-switched ROM gets 2MBytes/sec of incoming data. Since the...
by hexwab
Thu Oct 20, 2016 3:35 pm
Forum: software: classic games
Topic: BBC Chess
Replies: 38
Views: 3832

Re: BBC Chess

BigEd wrote:Very interesting tabulation - good find! Here are just the 6502 engines, sorted by strength:
[...]

Curious that you don't count the 65C02 as a 6502.
by hexwab
Thu Oct 20, 2016 3:16 am
Forum: software: classic games
Topic: BBC Chess
Replies: 38
Views: 3832

Re: BBC Chess

Assuming I haven't gone mad :shock: : For a very unique screen mode, you could also go in between with chunky pixels (double height mode 5 pixels) in four colours with a board 96x96 (12x12 pixels per square) using the linear addressing trick with 2 pixel high characters plus 6 lines of mode 7 text....
by hexwab
Fri Oct 14, 2016 11:37 pm
Forum: software: classic games
Topic: BBC Chess
Replies: 38
Views: 3832

Re: BBC Chess

Beautifully drawn - I really like those. =D> Thanks! Yes, 128x128 plus some MODE 7 was the idea. I pondered having extra border round the sides, possibly with some coordinates, but I don't think it would be required. (I'm by no means a strong chess player but it really doesn't take much practice to...
by hexwab
Fri Oct 14, 2016 2:20 am
Forum: software: classic games
Topic: BBC Chess
Replies: 38
Views: 3832

Re: BBC Chess

So I made a 16x16 chess set and a program to plot it. Here's what I started with: r1b2rk1_pp3ppp_1q6_1Bb5_3Nn3_8_PP3PPP_RNBQ1RK1.gif Here's how it looks on the beeb: chessbeeb.png The next step would be to integrate it with dp11's fancy MODE 7 split screen. Any takers? Total code+data weighs in at 7...
by hexwab
Tue Oct 11, 2016 12:00 am
Forum: software: classic games
Topic: BBC Chess
Replies: 38
Views: 3832

Re: BBC Chess

Here's some tiny bitmapped chess pieces: https://github.com/olikraus/u8glib/wiki/little_rook_chess My gut feeling is that mono is the way to go, as 4 horizontal pixels isn't really enough and there doesn't seem to be any way to do anything useful with just 1 or 2 control codes per square (=>8 or 6 p...
by hexwab
Wed Sep 28, 2016 4:12 am
Forum: software: other
Topic: Bitshifters present Beeb Tracker - new VGM music demos!
Replies: 48
Views: 5203

Re: Bitshifters present Beeb Tracker - new VGM music demos!

A good example where this is particularly obvious is "sonic enters a dance club". This tune has been used before on the beeb (in _Some Nasty Effects_) but at a higher pitch for precisely this reason. For this demo the tune is just played as-is without any re-tuning, so sending the data values from ...
by hexwab
Wed Sep 28, 2016 12:38 am
Forum: software: other
Topic: Bitshifters present Beeb Tracker - new VGM music demos!
Replies: 48
Views: 5203

Re: Bitshifters present Beeb Tracker - new VGM music demos!

My first thought was "keep the periods intact, and increase the tempo by 3% to account for tunes that rely on the default periods". But that doesn't take into account the 1/16 versus 1/15 duty cycle problem. Keeping the pitch where possible is probably a good idea. (But then what if you have a multi...
by hexwab
Tue Sep 27, 2016 1:17 pm
Forum: software: other
Topic: Bitshifters present Beeb Tracker - new VGM music demos!
Replies: 48
Views: 5203

Re: Bitshifters present Beeb Tracker - new VGM music demos!

One thing about the 3.58-to-4MHz clock rate conversion is that 3.58MHz tunes can use lower notes. The current converter tries to preserve pitch even if low notes end up clipped to the lowest possible frequency. This sounds terrible. Have you considered detecting clipping and shifting the whole tune ...
by hexwab
Tue Sep 27, 2016 3:51 am
Forum: community projects
Topic: Bitshifters - Ode to Mode 7 Competition
Replies: 43
Views: 3841

Re: Bitshifters - Ode to Mode 7 Competition

Here's a MODE 7 overscan thingy I made a few months ago but never got round to polishing. I don't have any good screens for it, nor did I ever get the OS to be happy writing to a non-contiguous memory layout. Still possibly of interest?

Tom.
by hexwab
Fri Jun 17, 2016 9:04 pm
Forum: adventures
Topic: Infocom adventures
Replies: 6
Views: 1618

Re: Infocom adventures

Yes. https://github.com/hexwab/zeugma . It's pretty lacking still. No split screen, no word wrap, no saving, no undo, no restart. (This explains the included game, which doesn't require any of these...) Somehow I haven't quite got round to implementing all the features that would turn this into a us...
by hexwab
Fri Oct 23, 2015 12:29 am
Forum: software: other
Topic: Enhanced mode 1 pictures
Replies: 108
Views: 13116

Re: Enhanced mode 1 pictures

Changing both colours takes 46 cycles, but a bit less from first register write to last. There are 128 cycles per scanline, with 80 of them visible, leaving 48 cycles to change the palette and allow for which of the 7 cycles in the BEQ+BIT the vsync starts. As I haven't seen any flicker, I either h...
by hexwab
Sat Jul 11, 2015 1:34 pm
Forum: emulators
Topic: Timings
Replies: 16
Views: 1961

Re: Timings

Yay!
by hexwab
Thu Jul 09, 2015 9:17 pm
Forum: emulators
Topic: Timings
Replies: 16
Views: 1961

Re: Timings

For me, the win condition would be people reading the article and toddling off to try it on their own. I imagine it would be a major letdown if interesting behaviour could only be observed on the setup provided. Not that speed control in jsbeeb wouldn't be useful for other reasons! While porting htt...