Search found 1153 matches

by Rich Talbot-Watkins
Wed Feb 21, 2018 3:51 pm
Forum: emulators
Topic: Double-clicking .SSD overrides VDU 14 ?!
Replies: 13
Views: 312

Re: Double-clicking .SSD overrides VDU 14 ?!

You could just add as your first line

Code: Select all

REPEAT UNTIL NOT INKEY-1


Will delay the program a bit on an emulator which keeps Shift held for a long time, but at least it fixes the issue!
by Rich Talbot-Watkins
Fri Feb 16, 2018 3:27 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

Yeah I don't think there's a way to discriminate odd and even fields on a Beeb (funnily enough, it *is* possible in B-Em and jsbeeb, because they set CA1 high half a scanline too soon on odd fields - little bug there). The only way you could do it is if you could see the HSync signal, and then time ...
by Rich Talbot-Watkins
Wed Feb 14, 2018 11:13 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

I may be wrong, but I didn't think the CPC464 had something like shadow screen memory. It just uses CRTC R12/R13 like we do in Beeb land. Whether it can address more than 32k of RAM is a different question I guess. Certainly 32k screens (as are occasionally used on the CPC) are already a hardware im...
by Rich Talbot-Watkins
Wed Feb 14, 2018 8:28 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

remember to set the sound volume to silent... Thanks tricky. Presumably this is the volume for tone generator 1 rather than the noise channel? It should be fairly easy for me to try this out so I'll give it a go in the next day or so. (I've just started looking at a CPC emulator so that's taking up...
by Rich Talbot-Watkins
Mon Feb 12, 2018 3:20 pm
Forum: software: games - high scores
Topic: keyboards on PC to play games: Ignored keys with other keys pressed
Replies: 13
Views: 340

Re: keyboards on PC to play games: Ignored keys with other keys pressed

I've long been of the view that most PC keyboards have this hardware limitation, and where multiple key rollover is important, you can buy "gamers' keyboards" which are sold with this as an explicit feature. I have a Corsair keyboard with Cherry Blue keyswitches for that nice clicky feel, ...
by Rich Talbot-Watkins
Thu Feb 08, 2018 4:57 pm
Forum: off-topic
Topic: Why did CISC prevail?
Replies: 21
Views: 582

Re: Why did CISC prevail?

Also the Thumb instruction set didn't provide access to the floating point instructions, so you had to switch back to regular mode each time you wanted to execute floating point (which, increasingly, was all the time).
by Rich Talbot-Watkins
Wed Feb 07, 2018 5:18 pm
Forum: software: other
Topic: BASIC weirdness
Replies: 9
Views: 315

Re: BASIC weirdness

You would need to preserve the value of ?xx and ?yy within the PROCinv call to completely match the previous behaviour.

So

DEFPROCinv(v1%,v2%)
LOCALoxx%,oyy%
oxx%=?xx:oyy%=?yy
?xx=v1%:?yy=v2%
....
?xx=oxx%:?yy=oyy%
ENDPROC

Anyway it sounds like you have a solution, so that's great!
by Rich Talbot-Watkins
Wed Feb 07, 2018 3:16 pm
Forum: software: other
Topic: BASIC weirdness
Replies: 9
Views: 315

Re: BASIC weirdness

It looks like the BASIC 2 bug where the PROC definition takes a parameter of type ?-operator. Check the definition of PROCinv - if it's something like DEF PROCinv(?&70, ?&71), that'll be what it is. I think it's overwriting some of the BASIC program with a bunch of zeroes which are invisible...
by Rich Talbot-Watkins
Fri Feb 02, 2018 2:13 pm
Forum: software: classic games
Topic: Most disappointing conversions from other systems
Replies: 51
Views: 1908

Re: Most disappointing conversions from other systems

There's also 3D Grand Prix, and I have a feeling there was yet another similar one to that too.

Edit: Chicane, that's the one.
by Rich Talbot-Watkins
Tue Jan 30, 2018 9:42 pm
Forum: software: classic games
Topic: Most disappointing conversions from other systems
Replies: 51
Views: 1908

Re: Most disappointing conversions from other systems

so from this general upbeat kind of thread I can infer that there certainly seems to have been some bad arcade conversions then lol :lol: :lol: Plenty of great ones too though! Skirmish is a near-identical version of Williams' Joust, and plays perfectly. Snapper (original release) was so close to P...
by Rich Talbot-Watkins
Mon Jan 29, 2018 12:11 pm
Forum: software: classic games
Topic: Most disappointing conversions from other systems
Replies: 51
Views: 1908

Re: Most disappointing conversions from other systems

Son of Blagger is appalling too. Apparently a port of a C64 original. OK, I know we didn't know the vertical hardware scrolling tricks at that point, but they probably ought to have not bothered with this port!
by Rich Talbot-Watkins
Fri Jan 26, 2018 10:04 pm
Forum: software: classic games
Topic: Most disappointing conversions from other systems
Replies: 51
Views: 1908

Re: Most disappointing conversions from other systems

Actually I think the arcade machine and faithful ports are 45 degrees scrolling - so 1 character block in MODE 1 / 2, and 4 pixels vertically. The CPC version seems to use an even more shallow angle - looks like only 2 pixels vertically! It has a graphical style that'd be interesting and unique to s...
by Rich Talbot-Watkins
Fri Jan 26, 2018 9:09 am
Forum: software: classic games
Topic: Most disappointing conversions from other systems
Replies: 51
Views: 1908

Re: Most disappointing conversions from other systems

I think Paperboy, which is also an Elite conversion, could also be massively improved. I've sometimes thought about doing it but I was never a great fan of the original. Yeah Paperboy's horrible. Exactly why they decided MODE 4 in blue and yellow was the right way to go, I have no idea. There was a...
by Rich Talbot-Watkins
Fri Jan 26, 2018 9:02 am
Forum: software: classic games
Topic: Most disappointing conversions from other systems
Replies: 51
Views: 1908

Re: Most disappointing conversions from other systems

For me, Atic Atac was one of those that was most disappointing on the Beeb. It just didn't seem right considering that it required a high number of colours and on the Beeb that meant MODE 2 with its fat pixels when compared to the Spectrum version. I used to love Atic Atac on the Beeb, though I had...
by Rich Talbot-Watkins
Thu Jan 25, 2018 10:05 pm
Forum: software: classic games
Topic: Most disappointing conversions from other systems
Replies: 51
Views: 1908

Re: Most disappointing conversions from other systems

I would have to nominate Green Beret for being a terrible conversion, and just a terrible game in general. It's just too fast to be even slightly playable, and that scrolling is horrific.
by Rich Talbot-Watkins
Tue Jan 23, 2018 6:35 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

Of course, the problem with implementing a true 4-bit/4-bit attribute mode is that it has 16 physical colours and so I can't do my border trick :( I think you still can: you just reserve logical colour 8 for the border, and have the parasite translate all 'bright' blacks to logical colour 0 instead...
by Rich Talbot-Watkins
Tue Jan 23, 2018 2:44 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

Also, I've lost track, what's the byte arrangement in screen memory when set up for Spectrum-style display? Using MODE 0 as the base suggests the Spectrum 1bpp display bitmap is mapped directly onto some of the BBC 1bpp display bitmap, but how are the attribute bytes mapped? Rob squeezed an extra a...
by Rich Talbot-Watkins
Tue Jan 23, 2018 1:09 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

So Rob, when are we going to see a video of this in action then? :)
by Rich Talbot-Watkins
Fri Jan 19, 2018 10:32 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

Thanks again. I'd thought to try a similar idea for the sound but didn't really think of it for the video. When I started writing this, I thought that I'd need to handle all the screen updates in one go but it may well be quick enough to do them in real time. The only thing I can think of that the ...
by Rich Talbot-Watkins
Fri Jan 19, 2018 8:40 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

JetSetWilly is a good test of LDIR as it uses two screen buffers: sets up buffer 1, LDIRs it to buffer 2, writes sprites to it, then LDIRs it to the screen. A common emulation of LDIR is to do it atomically within the emulator, so to the CPU it looks like it's instant. The symptom of this is things...
by Rich Talbot-Watkins
Fri Jan 19, 2018 8:14 am
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

I have another thought about synchronising screen writes on the host with those on the emulator. This is still based on the assumption that the host will always be able to process packets from the parasite, on average, in real time. The issue is that we want to ensure that actual screen writes on th...
by Rich Talbot-Watkins
Thu Jan 18, 2018 9:45 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

Just a further brain dump as I think of stuff. You might actually want to build in some delays on the parasite emulation so that you stay roughly in sync with real time at the end of every 8 lines or so. That would further mitigate flicker/tearing problems due to the host writing to the screen too s...
by Rich Talbot-Watkins
Thu Jan 18, 2018 9:37 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

Just to add, for purposes of timing, it might be worth knowing that the Spectrum ULA didn't output interlaced video. It was just 312 lines each field, or exactly 69888 T-states.
by Rich Talbot-Watkins
Thu Jan 18, 2018 9:29 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

I would think that your flicker is mostly caused by not syncing VSyncs on the host with your emulated HALT on the parasite. I would expect most games to use that to avoid flicker as much as possible, even those which have to present the back buffer via the SP or unrolled LDI techniques (as this can ...
by Rich Talbot-Watkins
Thu Jan 18, 2018 8:48 pm
Forum: hardware
Topic: SpectROM - Speccy emulator for the Pi co-pro
Replies: 113
Views: 3371

Re: SpectROM - Speccy emulator for the Pi co-pro

Just caught up with this thread. Great stuff Rob! On the subject of double buffering - I'm not sure it would be necessary, as I would have expected it to be possible to reflect the emulated screen state on the host in real time, as the emulation runs. You might need to make a few different cases for...
by Rich Talbot-Watkins
Wed Jan 17, 2018 8:13 pm
Forum: software: other
Topic: ASBAS Assembly Orientated BASIC
Replies: 5
Views: 291

Re: ASBAS Assembly Orientated BASIC

Wouldn't have really been useful for me - I used to use SIN/COS/SQR etc all the time for building tables and so on. In fact, that was one of my main reasons for writing BeebAsm in the first place - to have a 6502 cross assembler that could let me use these functions to build tables within my assembl...
by Rich Talbot-Watkins
Mon Jan 15, 2018 5:00 pm
Forum: programming
Topic: Many DEFPROC, 1 ENDPROC?
Replies: 17
Views: 1258

Re: Many DEFPROC, 1 ENDPROC?

If you want the compiler to be able to work out that it's safe to lift a strlen call out of a loop, you need it to know two things: ⋅ strlen() is a pure function (it has absolutely no side effects; it's impossible to tell if you called it once or twice) ⋅ The string its argument...
by Rich Talbot-Watkins
Mon Jan 15, 2018 2:30 pm
Forum: programming
Topic: 32k memory management for dummies
Replies: 28
Views: 931

Re: 32k memory management for dummies

OS 0.1 had *NOTAPE, which I assume deselected the filing system. Presumably they considered it useless enough to remove!
by Rich Talbot-Watkins
Mon Jan 15, 2018 2:21 pm
Forum: programming
Topic: Many DEFPROC, 1 ENDPROC?
Replies: 17
Views: 1258

Re: Many DEFPROC, 1 ENDPROC?

Of course, in this example, you'd be even better just writing: for (i = 0; s[i] != 0; i++) { x = s[i]; ... } to save iterating through the string twice (once in strlen, once in the loop). Edit: I previously stated that the compiler could be clever enough to hoist the strlen out of the loop if it mee...
by Rich Talbot-Watkins
Mon Jan 15, 2018 8:19 am
Forum: programming
Topic: BeebAsm's Hello World - printing part of file name, not "Hello World"
Replies: 13
Views: 448

Re: BeebAsm's Hello World - printing part of file name, not "Hello World"

tom_seddon wrote:I keep putting off thinking about this, but github sent me an email about the new PR, so I suppose I just have to admit it: I've been a terrible steward of this project :(

Not as bad as me! :lol: