Search found 172 matches

by Joefish
Wed Apr 18, 2018 12:52 pm
Forum: Programming
Topic: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum
Replies: 27
Views: 509

Re: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum

Nope, I deliberately set out to undermine all your hard work in this thread. :D
by Joefish
Wed Apr 18, 2018 10:06 am
Forum: Programming
Topic: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum
Replies: 27
Views: 509

Re: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum

There is an alternative, which is to write your code with the right timing built-in to its execution time, and synch it to the interrupt. But you do have to identify the machine you're running on to get the timing right. There are various approaches to make sure your code always takes the same time ...
by Joefish
Tue Apr 17, 2018 6:07 pm
Forum: Programming
Topic: Double buffering on the Spectrum
Replies: 40
Views: 852

Re: Double buffering on the Spectrum

I didn't fully appreciate that Sidewize / Crosswize run at 50fps. That's a lot of scenery and sprites being redrawn. I can see that Sidewize uses a block of scenery that repeats several times across the screen, and I know Crosswize multi-loads, so it's probably not being super-efficient with memory,...
by Joefish
Tue Apr 17, 2018 5:48 pm
Forum: Programming
Topic: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum
Replies: 27
Views: 509

Re: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum

One thing to keep in mind, though. Contention only applies to the code running in contended memory (that’s why it’s called that). Code running elsewhere is unaffected and the CPU is running at full speed all the time. Totally forgot about that! :lol: Thanks for putting all this together. It'll be f...
by Joefish
Tue Apr 17, 2018 5:10 pm
Forum: Programming
Topic: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum
Replies: 27
Views: 509

Re: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum

If you’re referring to the +2A/+3 code, then the port itself doesn’t seem to be contended. The LD A,(NNNN) instruction is what affects the timing, as reading from a non-contended address will break the sync. I was asking about both, so what about the 48K code? Is Ersh right? Doesn't the contention ...
by Joefish
Tue Apr 17, 2018 4:48 pm
Forum: Design/Ideas
Topic: Jesus Christ:Monster killer
Replies: 13
Views: 418

Re: Jesus Christ:Monster killer

If it was an FPS you wouldn't have to depict the main character...
by Joefish
Tue Apr 17, 2018 4:36 pm
Forum: Programming
Topic: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum
Replies: 27
Views: 509

Re: The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum

Interesting. But you mention the timing is critical to be sure of reading attribute bytes rather than pixel bytes, but don't explain what that timing depends on. I don't know, but here's a guess - are you relying on contention of the IN instruction itself? Also, presumably you could plant the value ...
by Joefish
Tue Apr 17, 2018 4:15 pm
Forum: Programming
Topic: Double buffering on the Spectrum
Replies: 40
Views: 852

Re: Double buffering on the Spectrum

Joffa did give some loose notes on how he did his scrolling, but they were such that you'd only really understand it if you tried to program it yourself. I had a few private exchanges with him and here are the basics that I gleaned. I didn't actually get anything from him about the floating bus, so ...
by Joefish
Sun Apr 15, 2018 6:51 pm
Forum: Announcements
Topic: Buzzsaw+ finally available on cassette!
Replies: 5
Views: 188

Re: Buzzsaw+ finally available on cassette!

There were to be some extras but all the stuff I wanted didn't come together. Some of the artwork has been mislaid, and I never finished my developer diary write-up. I figured it was time to stop mucking about and get it on tape. I might put out the free version source code at some point.
by Joefish
Sun Apr 15, 2018 4:10 pm
Forum: Announcements
Topic: Buzzsaw+ finally available on cassette!
Replies: 5
Views: 188

Re: Buzzsaw+ finally available on cassette!

Nor in the production of the cassette inserts.
But we had to force-feed the squid some pretty weird sh*t to get the right coloured inks. :mrgreen: