Spectrum Computing

Waldroid wrote: ↑Tue Aug 15, 2023 1:13 pm Yes please!

Well, which one?

Waldroid wrote: ↑Tue Aug 15, 2023 11:33 amSabre Wulf?

Nope.


Do you, gentlemen, want a clue or a zoomed out snippet?

sn3j wrote: ↑Mon Aug 14, 2023 8:46 pm I was thinking Dynatron but can't really place it.

No, it’s a slightly earlier game.

Lee Bee wrote: ↑Sun Aug 13, 2023 2:33 pm When someone gets it right, I always like to see the full screenshot. Do others agree that it would be nice if we could all try to reveal the full screen, when convenient?

Sure, why not?

Anyway, here’s a bigger crop:

Van_Dammesque wrote: ↑Sun Aug 13, 2023 9:31 am Wheelie?

Nope, but I see now how it might look reminiscent of that.

Right. On your mark, gentlemen!

Batty.

(That’s the ball deflecting thingy from Level 2, I believe.)

it works fine on an old SCART-capable LCD TV, so whatever's out-of-spec isn't out-of-spec enough to confuse an old TV. Well, you kind of answered your own question. The Spectrum’s video signal is quite quirky. Some newer TVs can handle it; some can’t. Older (analog) TVs are perfectly fine with it, ...

Looks like the Z80 is not operating; could be dead. Check its power supply and clock (if you happen to have an oscilloscope).

Pull out the ROM and/or try the diagnostic ROM again.

Do the contents of the display change in any way when you press the reset button?

It would be great if you could test the system over the RGB connection, although I suspect the results will be identical. Now, this got me thinking that the problem might lie with one of the switching ICs (such as IC27, IC29, or IC30) and associated circuitry. I looks like the CPU can read and write...

A thought occurs . . . How do you have the machine connected to the TV—via RGB or RF?

It is indeed a stuck key. If it’s mechanical (i.e. the membrane or the key caps themselves), you could try gently pushing on each key and wiggling it around a bit.

I’m not entirely convinced it’s the RAM, but from the pictures you posted it looks like it’s either IC 22 or IC 13. If you don’t have spares, try swapping them with any other RAM IC and see if the vertical lines change position.

Flatulentia wrote: ↑Thu Jul 27, 2023 1:31 am Update time...

I've just created an 11025bps turboload file of one of my favourite Speccy games with OTLA and it loads fine from my smartphone via the input circuit as described above.

Neat. That’s a good test.

Flatulentia wrote: ↑Wed Jul 26, 2023 8:57 pm The opamp and its associated components form a simple bandpass filter that attenuates signals below 150Hz and above 4.5kHz.

4.5 kHz, isn’t it a tad low? Some turbo loaders go way past that cutoff frequency.

SkoolKid wrote: ↑Thu Jul 20, 2023 8:19 pm I haven't been able to get Fuse to LOAD and run these games either.

You mean the tape versions? Because I just tried the TR-DOS version of Figus in Fuse and it loaded and ran fine.
The tape versions might be automatic conversions, likely untested to begin with.

Well, I’ll be a monkey’s uncle, but I did manage to crack the Alkatraz copy protection and squeeze in the code for the +2A/+3 crash workaround. Took a whole lot of manual assembly and encryption. Bleepload is child’s play in comparison. I also optimized my original code a little bit. Played the game...

Bloody Alkatraz!

But I think I beat it. Will probably release the bug-fixed TZX tomorrow. Stay tuned.

Cool.

I’ve optimized my patch even further, and figured out where to place the bits and pieces inside the original release. Now, the tricky bit will be the reverse engineering of the original loader and decryptor. That’ll take some time.

Well, it’s tricky. The game crashes because the developers mess around with the IY register while allowing the native interrupts to run. The IY is modified three or four times during the game, so instead of treating each case individually, it’d make sense to write a custom ISR along these lines: pus...

one of my practicals/projects was a submission of a ZX Spectrum program (drawing mathematical graphs) on a cassette tape, along with a listing. An impressive curriculum you had, if I do say so myself! None of my schools (I attended several) had anything remotely like that. (A couple of them did hav...

Ho–o–old up!

Am I the only one who actually used his Speccy to help with the homework?

Seriously, graphing trigonometric functions and parabolas was both fun and educational, and really served as a great visual guide.

Gooeyblob wrote: ↑Sat Jul 01, 2023 2:26 pm @Ast A. Moore @FrankT
Have you seen this?
https://github.com/ZoomTen/chronos-zxbeeper

Ha, no, I haven’t. Thanks! Will give it a read.