Search found 1743 matches

by BigEd
Fri May 25, 2018 9:06 pm
Forum: off-topic
Topic: Forum GDPR compliance?
Replies: 55
Views: 579

Re: Forum GDPR compliance?

That's good info - thanks!
by BigEd
Fri May 25, 2018 5:37 pm
Forum: off-topic
Topic: Forum GDPR compliance?
Replies: 55
Views: 579

Re: Forum GDPR compliance?

Good luck!
by BigEd
Fri May 25, 2018 4:08 pm
Forum: off-topic
Topic: Forum GDPR compliance?
Replies: 55
Views: 579

Re: Forum GDPR compliance?

I see the plugin's text as linked by Russell declares that a member's posts are considered public information, as they will have been indexed and may have been archived by third parties. So, one's posts are not affected by GDPR. I agree with the idea that it's unwelcome for a user to delete their co...
by BigEd
Fri May 25, 2018 11:03 am
Forum: software: new games
Topic: New version of Scramble for the beeb (going well)
Replies: 36
Views: 1719

Re: New version of Scramble for the beeb (just starting)

Visual 6502 have a 6845 in their queue but haven't started decapping it yet. I did ping the list: it doesn't sound like there's any activity on the 6845. Incidentally, this documentation has the following snippet about different CRTC types... As a possibly useful addition to that, André has pointed...
by BigEd
Fri May 25, 2018 10:20 am
Forum: off-topic
Topic: Forum GDPR compliance?
Replies: 55
Views: 579

Re: Forum GDPR compliance?

I see mentions of 'economic activity' as being relevant to the GDPR - we don't have membership fees and stardot as a forum isn't any kind of business. So possibly exempt? (Then again, it's not a personal or household activity...) Any business conducted on the forum - buying, selling, subs for meetup...
by BigEd
Thu May 24, 2018 4:12 pm
Forum: software: other
Topic: Border tracing Mandelbrot generator for the Beeb
Replies: 70
Views: 5200

Re: Border tracing Mandelbrot generator for the Beeb

(Note the implicit use of D% and C%)
by BigEd
Thu May 24, 2018 1:34 pm
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 18
Views: 438

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

BTW, for the cost of a couple of base-2 logs, which is almost nothing, surely, in binary, and with the addition of a VideoNULA, it's possible to apply smooth shading to the display. See here
http://linas.org/art-gallery/escape/smooth.html
by BigEd
Thu May 24, 2018 1:31 pm
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 18
Views: 438

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

There's another idea which I'm failing to find in my searches- a little like the boundary following, expect it draws a small circle around each computed point. In areas of less detail, it turns out the circle is not so small, of course. The net effect, mathematically justified, is needing to compute...
by BigEd
Thu May 24, 2018 1:29 pm
Forum: software: other
Topic: Border tracing Mandelbrot generator for the Beeb
Replies: 70
Views: 5200

Re: Border tracing Mandelbrot generator for the Beeb

Oh hang on, that does rather more work than I thought!
by BigEd
Thu May 24, 2018 1:17 pm
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 18
Views: 438

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

That's a cool technique! So, we have: Z re ' = Z re 2 - Z im 2 + C re Z im ' = 2 Z re Z im + C im        = ( (Z re + Z im ) 2 - (Z re - Z im ) 2 ) / 2 + C im That way, all the squares come directly from the table. Four squarings... it turns out , I think, that three squarings are enough: The one mu...
by BigEd
Thu May 24, 2018 12:06 pm
Forum: software: other
Topic: Border tracing Mandelbrot generator for the Beeb
Replies: 70
Views: 5200

Re: Border tracing Mandelbrot generator for the Beeb

Dave [hoglet] and I just had a bit of a chat about Mandelbrot speedups as a consequence of the 12-second Mandelbrot thread ... which now contains a very interesting idea using 13 bit arithmetic and a big table of squares. (I wonder if perhaps the next step on those lines is 24 bit numbers, treated a...
by BigEd
Thu May 24, 2018 8:31 am
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 18
Views: 438

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

Very nice! (I think I'd call it 13 bits, but still.)
by BigEd
Wed May 23, 2018 9:30 pm
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 18
Views: 438

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

Very good indeed - what's the secret sauce?
by BigEd
Mon May 21, 2018 7:28 pm
Forum: programming
Topic: 12-second Mandelbrot rendering on the BBC Master!
Replies: 18
Views: 438

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

Excellent - thanks for the jsbeeb link! (And thanks for the detailed writeup too. It's interesting to see different tradeoffs in arithmetic.)
by BigEd
Thu May 17, 2018 5:03 pm
Forum: hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)
Replies: 1056
Views: 91580

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)

Thanks for the new pre-release Dave!

(This is an actual egg-eater doing its thing.)
by BigEd
Mon May 07, 2018 3:32 pm
Forum: hardware
Topic: Beeb PAL encoder mystery solved?
Replies: 7
Views: 460

Re: Beeb PAL encoder mystery solved?

Ah, yes, thanks - I think I see now, that luma reaches the modulator from Q8 (or the BNC from Q7), whereas chroma comes from Q9.
by BigEd
Mon May 07, 2018 10:54 am
Forum: hardware
Topic: Beeb PAL encoder mystery solved?
Replies: 7
Views: 460

Re: Beeb PAL encoder mystery solved?

Would those resistors improve the monochrome contrast for a monochrome screen? I've had about four monochrome screens - two monitors, two TVs - and still have them, somewhere. I didn't have a colour monitor, or a colour TV, BITD, although I might have had one right at the end of my Beeb's first run ...
by BigEd
Fri May 04, 2018 12:37 pm
Forum: hardware
Topic: RiscPC Second CPU slot ARM possible?
Replies: 8
Views: 601

Re: RiscPC Second CPU slot ARM possible?

I suppose the cooperation which the x86 copro performs must be well-enough understood these days, so any copro which played by the same rules would be able to share memory and screen with the host OS?
by BigEd
Fri May 04, 2018 12:36 pm
Forum: hardware
Topic: Beeb PAL encoder mystery solved?
Replies: 7
Views: 460

Re: Beeb PAL encoder mystery solved?

R154 and R148 look like a slightly different thing - but it's beyond me! (Not that I'm saying there's no similarity, just curious about the circuit.)
by BigEd
Wed May 02, 2018 4:47 pm
Forum: software: classic games
Topic: My final unanswered Exile question
Replies: 61
Views: 2745

Re: My final unanswered Exile question

Maybe a perfect hash function, as first seen in 1984?
by BigEd
Wed May 02, 2018 4:20 pm
Forum: off-topic
Topic: Thermionic Valves
Replies: 59
Views: 2905

Re: Thermionic Valves

That's a Magic Eye, I think. A kind of VU meter.
https://www.youtube.com/watch?v=Zt3IY6Jxtjs

I saw one on a domestic reel to reel recorder in the early 70s (probably). Fascinating!
by BigEd
Tue May 01, 2018 1:59 pm
Forum: off-topic
Topic: Messing about with 6507 CPUs...
Replies: 5
Views: 283

Re: Messing about with 6507 CPUs...

There's a just-finished retrochallenge to write a 2600 game here:
http://www.masswerk.at/rc2018/04/

With a demo in the browser, and a gadget ("synth") to experiment with 2600 sounds - and even that, to have a GUI, needs a cycle-accurate display kernel.
by BigEd
Tue May 01, 2018 7:14 am
Forum: off-topic
Topic: Need some electronics advice...
Replies: 20
Views: 694

Re: Need some electronics advice...

I'd go for 2 and 3. If you've got a relay nearby, you've got a very electronics-unfriendly environment, and a capacitor or two (one big, one small) helps to keep things peaceful. You might also look at your power wiring: separate wires from the supply to the heavy duty stuff on one hand, and to the ...
by BigEd
Mon Apr 30, 2018 9:38 pm
Forum: general
Topic: The Beeb's (first) 32-bit second processor on TV
Replies: 16
Views: 651

Re: The Beeb's (first) 32-bit second processor on TV

I did - good read - thanks!
by BigEd
Mon Apr 30, 2018 8:07 pm
Forum: general
Topic: The Beeb's (first) 32-bit second processor on TV
Replies: 16
Views: 651

Re: The Beeb's (first) 32-bit second processor on TV

Ah good - something I'm happy to be wrong about! Thanks Dave.
by BigEd
Mon Apr 30, 2018 7:44 pm
Forum: general
Topic: The Beeb's (first) 32-bit second processor on TV
Replies: 16
Views: 651

Re: The Beeb's (first) 32-bit second processor on TV

Am I right in thinking the Elk only got Tube capability in recent years?
by BigEd
Mon Apr 30, 2018 4:29 pm
Forum: hardware
Topic: Master + VideoNuLA + internal PiTubeDirect, but won't turn on
Replies: 7
Views: 295

Re: Master + VideoNuLA + internal PiTubeDirect, but won't turn on

That's great! I've heard that unwanted threads of solder can be almost invisibly small.
by BigEd
Mon Apr 30, 2018 3:29 pm
Forum: hardware
Topic: Master + VideoNuLA + internal PiTubeDirect, but won't turn on
Replies: 7
Views: 295

Re: Master + VideoNuLA + internal PiTubeDirect, but won't turn on

Sounds possible you've got a short across the power supply - can you measure voltages?
by BigEd
Fri Apr 27, 2018 8:13 pm
Forum: software: other
Topic: BBC Micro Compendium by Jeremy Ruston
Replies: 25
Views: 592

Re: BBC Micro Compendium by Jeremy Ruston

Well done!
by BigEd
Fri Apr 27, 2018 4:05 pm
Forum: software: other
Topic: BBC Micro Compendium by Jeremy Ruston
Replies: 25
Views: 592

Re: BBC Micro Compendium by Jeremy Ruston

We used wolframalpha.com to expand the expressions as a Taylor series, and one could then see how they come up with the right series. What that doesn't tell you is how to get from a Taylor series to a continued fraction! Nor how to tweak it, if necessary, to improve accuracy over a limited range. Ca...