Spectrum Computing

Am I understanding correctly that the 6502 depacker is not compatible with output from the original compressor?

The main reason for the parasite tone here will probably be the fact that this loop is not timing-stable, because of IO contention. Aligning the output to a multiple of 8 t-states should improve the result somewhat, but there will still be whine. di xor a ld bc,0x10fe ld hl,loop loop: xor b ;4 out (...

P.S. It’s not a good idea to concatenate TAP files, because aside from actual data, they contain additional information relevant to the container itself. You’ll end up with a bunch of garbage at the “joint” of the files. Is that really true? The .tap format is pretty much made to facilitate concate...

Do you have an example of that? I know [mention]RMartins[/mention] tried a couple of years ago, and it was just barely working (for mixing two channels). It's unfeasible for two reasons, first of all because it takes too much memory, and second of all because the Speccy is barely fast enough for the...

This is interesting: http://www.robeesworld.com/blog/58/pulse-width-modulation-how-1-bit-music-works It shows how a sine wave can be cut up into varying hi/lo cycles at a fixed rate (Pulse Width Modulation). For replay, this relies on the smoothed response of the speaker circuit. Is there a similar...

A third method is open to you if you have other processing hardware. You convert the sound into a very fast stream of dithered bits that rely on the resistor/capacitor circuit of the Speccy's speaker to smooth them out into an audio waveform. Though I've never seen any software that can generate th...

Fantastic work, thanks a lot Einar! Running a few tests shows that ZX0 works very well for my most common use case, compressing data for music players. Very exited to see something that can beat apack.

The checksums for the Speccy ROM files required by MAME have not changed since the MESS merge in 2012, so the ones you have will most likely work just fine.
https://github.com/mamedev/mame/blame/b ... ectrum.cpp

Congratulations on reaching this milestone! Excellent work. I think your current data layout would indeed be fine as is, provided you use an order list with it (not just one single long pattern). Any chance for releasing the source code? Preferably under a permissive license (MIT, BSD, WTFPL), would...

A big fat thumb up from me, too. Outstanding work.

Works for me now

I can confirm the issue. The cert seems valid for https://spectrumcomputing.co.uk only. Nothing to do with Google, happens when typing www... directly into the address bar. www.spectrumcomputing.co.uk uses an invalid security certificate. The certificate is only valid for spectrumcomputing.co.uk. Er...

Ha, that actually looks like you're past the "learning Assembly" stage, and are now headed for the "having fun with Assembly" stage

Hmm, "micro", that's something I could get behind, too.
Other than that, "lite" is still my one of my favourites (though it basically was rejected already), and of course [mention]Juan F. Ramirez[/mention]' glorious "16K".

Juan F. Ramirez wrote: ↑Tue Jul 14, 2020 11:21 pm 16K

We have a winner.

In other words, it's disabled by default in assembly

Media queries are so 2019 flex-grow/flex-shrink is all the hype now.

Another vote for the v3 banner, btw. In fact I'd like it to be even smaller.

Also +1 to @8BitAG's suggestion. I'm rather allergic to the word "retro". I don't get why you guys don't like word "retro". Personally I have no problem with calling myself and my interests retro, oldschool and vintage ;) And people seem generally to like this words too. Especia...

If anyone has need for music for a custom AY player for which no dedicated editor is available, I will be able to support those in Bintracker soon (in a couple of months). So just get in touch if need arises!

Here's an initial version: https://spectrumcomputing.co.uk/retro/4087 It should work for any game page URL from SC, just replace "entry" with "retro". I know some fields are still missing, don't worry about it, I will take care of these details later. Next step will be adding a ...

Difficult to say without seeing the code. Perhaps you could post it somewhere so people on here can take a look?

+1 to what [mention]akeley[/mention] said. As has been demonstrated countless times in the past, Lee and his clique aren't interested in a rational discussion, so arguing with them is a waste of time. Other than that there's no need to defend yourself [mention]Einar Saukas[/mention], you've done mor...

It's especially helpful in cases like the one you were struggeling with with "and 31" and "first 8K of ROM". The decimal numbers 31 and 8191 tell you nothing. 0x1f and 0x1fff on the other hand immediately let you see that you don't need to worry about the low byte. Or take PeterJ...

"8K" = 8192 bytes. So the first "8K of ROM" means an address between 0 and 8191. 8191 = %11111 11111111, or 0x1fff. We don't need to worry about the lower 8 bits, since they may take any value. The upper 8 bits on the other hand must have a value between 0 - %11111, or 0 - 0x1f, ...

a) does this have bias on larger numbers (ie. if a>=31; AND 31 would always equal 31 ???)? No. A logical AND operates on individual bits. The result of ANDing two bits is 1 if and only if both of the pair of bits are 1. %00110001 (= 49 decimal) AND %00000111 (= 7 decimal) ========================= ...