Search found 60 matches

by IanB
Sat Aug 08, 2015 10:27 am
Forum: ZX Spectrum Lounge
Topic: Guys, can you tell me what these numbers mean?
Replies: 10
Views: 6599

Re: Guys, can you tell me what these numbers mean?

That appears to be the right answer!
by IanB
Fri Aug 07, 2015 10:05 pm
Forum: ZX Spectrum Lounge
Topic: Guys, can you tell me what these numbers mean?
Replies: 10
Views: 6599

Re: Guys, can you tell me what these numbers mean?

I'm just thinking it's hard to even guess, without knowing how the whole engine works. What happens if you change these bytes? You can sometimes find out what something does by breaking it, if you see what I mean.
by IanB
Fri Aug 07, 2015 1:56 pm
Forum: Software
Topic: VULCAN EXPANSION PACK - now with even MORE content
Replies: 4
Views: 11683

Re: VULCAN EXPANSION PACK - now with even MORE content

This must have been a major project Daniel!
by IanB
Fri Aug 07, 2015 12:35 am
Forum: Development
Topic: Executing code in extended memory
Replies: 20
Views: 6255

Re: Executing code in extended memory

Well, I haven't tested this, but I think the problems would only occur if you did editing in BASIC on the machine and it called the MAKE-ROOM routine in the ROM that shifts the display file, variables area etc. I have done an experiment of having the machine flip between two display files on each fi...
by IanB
Thu Aug 06, 2015 10:42 pm
Forum: Development
Topic: Executing code in extended memory
Replies: 20
Views: 6255

Re: Executing code in extended memory

Come to think of it, if you've got more than 16K I presume you could just move the whole Display File up above 16K, and have another 793 bytes available for program code :)
by IanB
Thu Aug 06, 2015 9:31 pm
Forum: Development
Topic: Executing code in extended memory
Replies: 20
Views: 6255

Re: Executing code in extended memory

If you're not using BASIC, I don't see much point in fiddling about with RAMTOP. You can just use the memory as you like above the display file so far as I can tell as a flat memory space (up to the 16K barrier anyway). You can even have multiple display files come to that, or a "long" display file ...
by IanB
Thu Aug 06, 2015 1:26 pm
Forum: Development
Topic: Executing code in extended memory
Replies: 20
Views: 6255

Re: Executing code in extended memory

I wonder if there was a better engineering solution to "Jim Westwood's Problem" for the same price in 1981 that could have been achieved. For instance, not limiting memory to 16k, allowing code execution in all the side screen margins, etc.
by IanB
Thu Aug 06, 2015 12:15 pm
Forum: Development
Topic: Time Available For Application Code On ZX81
Replies: 22
Views: 7643

Re: Time Available For Application Code On ZX81

Yes, I'm working lo-res and the standard display. The intention is full screen graphics in 1K, among other things. This means judicious use of short lines :)
by IanB
Thu Aug 06, 2015 11:54 am
Forum: Development
Topic: Time Available For Application Code On ZX81
Replies: 22
Views: 7643

Re: Time Available For Application Code On ZX81

Well I'm targetting 16000 at the moment. It's quite crucial to me because I need a dynamic display file, and moving bytes takes a lot of clock cycles :( 21 per byte for an LDIR, you can shave some off with an LDI block and fewer loops, like LDI LDI LDI LDI jp pe, LOOP -that is 18.5 clocks per byte, ...