Search found 23 matches

by hexwab
Sun Jun 04, 2017 6:11 pm
Forum: emulators
Topic: Games turn off interlace mode
Replies: 21
Views: 767

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: 767

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: Starting a Prince of Persia port...
Replies: 21
Views: 1147

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: 30
Views: 2386

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: 158

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: 1194

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: 154

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: 154

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: 2077

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: 2077

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: 2077

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: 2077

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: 2077

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: 2638

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 va...
by hexwab
Wed Sep 28, 2016 12:38 am
Forum: software: other
Topic: Bitshifters present Beeb Tracker - new VGM music demos!
Replies: 48
Views: 2638

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 ha...
by hexwab
Tue Sep 27, 2016 1:17 pm
Forum: software: other
Topic: Bitshifters present Beeb Tracker - new VGM music demos!
Replies: 48
Views: 2638

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: 2104

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: 637

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: 98
Views: 7369

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: 1328

Re: Timings

Yay!
by hexwab
Thu Jul 09, 2015 9:17 pm
Forum: emulators
Topic: Timings
Replies: 16
Views: 1328

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...
by hexwab
Thu Jul 09, 2015 1:53 pm
Forum: emulators
Topic: Timings
Replies: 16
Views: 1328

Re: Timings

Awesome. sweh, thanks for testing on real machines. Matt, thanks for looking into fixing jsbeeb (and you are welcome to use this as part of the test suite). Yes, TIME is *not* reporting centiseconds. But I had no idea what might've been causing such a discrepancy: ADC never even occurred to me. If I...
by hexwab
Wed Jul 08, 2015 10:03 pm
Forum: emulators
Topic: Timings
Replies: 16
Views: 1328

Timings

So I imagined emulator timing would be pretty much sewn up at this point. Not so! Here's a simple test case that can reliably distinguish between every emulator I've tried. (The verdict on real hardware is still out: my PSU is in need of magic smoke replacement.) It would be good to get some consist...

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