stardot.org.uk

And loads fine in jsbeeb too!

acorn wrote: ↑

Wed Sep 18, 2019 5:32 pm

Is this tape still available somewhere? The whole site went out of existence ...or at least seems to have changed purpose.

It's been reuploaded here a few times I think, and here's one of them!
viewtopic.php?t=5023#p86170

Then you just have to consider the decryption step (for which you have the code, unencrypted) part of the loading process. As long as you call the decryption routine once, probably before saving but maybe after reloading, you should be good to go. I suppose if the last chunk of code loaded from the...

Yeah, we talked about Star Clash once before on here. I personally doubt that it shared any code in common with Elite, because it runs at a much worse frame rate and the ships are far more simplistic. But clearly the look and feel of the game is very much 'inspired' by Elite, and it got withdrawn fr...

BBC Micro only Stryker's Run How did you deal with stuff like Stryker's Run which had to be compatible with more than just OS 1.20? You couldn't have used your 'nasty' protections from Ultimate I guess, but I did notice the Kevin Edwards signature lock-up where it spends 4 seconds decrypting stuff!...

In the case of a '2MHzE even' clock shape, it does look like there's a falling edge on 1MHzE a full cycle before time Q, and yes, I would expect the 6502 and glue logic to have done all the necessary things by this time. (I say that without having studied the schematic.) Is this what's being allude...

Ah, yeah. And I see it in the circuit diagram now as well.

Do you think there's any possibility it might be happening on the 1MHz cycle before Q, or is that too premature for the CPU to have set things up?

Thanks for your expertise!

There are two cases for the clock crossing. Only one is shown in the NAUG (and App note 3). The other one is the low phase of the 2MHzE is 250ns and high phase is 750ns (75% duty cycle). The falling edge of 1MHzE and 2MHzE always coincide. Writes from CPU -> device latch at this falling edge. The C...

I'd always thought it was just the high clock period (T...U here) that got stretched, as per Matt's jsbeeb article: https://xania.org/201405/jsbeeb-getting-the-timings-right-cpu - but this diagram appears to show the low clock period stretched too! Unfortunately I don't have the skills to figure ou...

Even better, if anyone can see with a scope what's going on with the 6502 A15, phi1, phi2 and R/W pins, and with the 6845 CLK, R/W, E and /CS pins while this program runs, that'd be amazing information! 10 MODE 0:REM high clock mode 20 P%=&900:[OPT2:SEI:.loop LDA #0:STA &FE00:LDA #80:STA &FE01:JMP l...

That's not exactly my understanding of it. This diagram from the AUG http://forum.6502.org/download/file.php?id=1523&sid=cd810fa2d59407c2b4e2005f7795a7df&mode=view shows that it's not switching in the 1MHz clock so much as actually stretching one cycle over three. It is certainly deterministic; if y...

Throwing a question out there to anyone who understands this hardwarey stuff more than I do. The 6845 CRTC can operate on the Beeb at two clock speeds - 1MHz and 2MHz - according to bit 4 of the Video ULA. I assume this controls not just its character clock rate, but also the rate at which its regis...

OSBYTE 160,96 returns the colour mask - the maximum number of colours minus 1 (which will be zero for MODE 7). Although that's also reading a VDU variable, so that's as tied to an Acorn 8-bit platform as reading the current mode via VDU variable &55. On RISC OS you'd do it via SWI OS_ReadModeVariab...

If you're interested in a challenge/mystery, perhaps you could look at why the original Battletank release (e.g. the tape version here ) didn't work on a Master. I never figured it out - it just gets to the title page and then hangs when you press fire to start. The disk version works OK, and I assu...

That's just what I did earlier, thanks, as well as trapping screen clears. You have a good memory as there was also an IRQV restore to fix. Some of those are perverse: they sometimes go to the trouble of saving the old vector as an exit point but don't use those values to do any restoration, prefer...

Note also the inputs to IC23 which determine which of the 32 byte blocks of SHEILA get cycle stretched access!

Thanks for the confirmation. Coincidentally it was Contraption that I was looking at. Unfortunately the Master zero page locations don't seem to be comprehensively documented anywhere that I can see. The MRF(1) only lists D0-FF as MOS workspace (as does the ARM). The NAUG gives the usual Model B de...

scarybeasts wrote: ↑

Wed Sep 04, 2019 9:40 am

?&FE2F=0
?&FE24=0
?&FE20=0

If you're aiming to hit the Video ULA control register and not the palette, that first one should be ?&FE2E=0.

No, the Master doesn't use a table - it just has the row multiplication hard coded - so there's nothing you can do unfortunately. I remember this exact problem with the game Contraption, and the only viable patch was to actually change all the VDU 31 OSWRCH calls to position the cursor at the right ...

What's up with that Sinclair Scientific exactly?

http://files.righto.com/calculator/sinc ... lator.html

3.1415
cos

9.9546 10

??

Quick look at the datasheet, and it seems like the 8271 can return "Drive Not Ready" if the drive is not powered up, the disk is not loaded or a non-existent drive is accessed. So no idea why Acorn's DFS doesn't respond to it.

for some reason the 8 bit filling systems never seem to have a timeout and will just sit waiting forever. Actually, that's something I've never really thought about. If you send the 8271 a command when there's no disk in the drive, will it return an error result, or will it just stall and wait for ...

That's part of the psychic abilities. How does the person writing the program know that there's a filing system number 73 which is selected with the *ZEEBAR command, but must be selected with the *XEBURE command to prevent it attempting to electrocute nearby cats on selection? How did that get out ...

?&257 non-zero means output is being spooled, so I guess you can just check that in an OSWRCH trap. I agree that this is surely the neatest and most automatic way of capturing test results.

Don't really see the problem with hooking OSWRCH to be honest. It means you can write a perfectly normal test on real hardware (and display the results), and then run the same thing on an emulator and capture the results (and compare with your ground truth). Most of the tests we have are BASIC snipp...

Can you not create a 'test' variant of your 6502 emulation which traps PC=&FFEE and records the accumulator on each call? This is the approach I'd take in any case.

Thanks for the advice. I was intending to optimise going forward, using look up tables and fixed point arithmetic to replace the floating point code. Even divide and multiply makes me worry when I'm updating thousands of vertices each frame! Yeah, exactly. You can't get around divide when doing per...

I would highly recommend for performance that you use fixed point representation for your matrix maths, and use a sine table to lookup sines/cosines rather than calculating them with sinf()/cosf(). Also, remember there are some nice trig identities you can use to avoid multiplications: e.g. sin A * ...

Looks much nicer graphically than the version which eventually arrived for the C64! Thanks for that!

Elminster wrote: ↑

Fri Aug 09, 2019 4:13 pm

They probably dropped the 'u' to save printing costs

Nonsense, everyone knows that the correct spelling is coloueur.