Master 128 - obscure video issue?

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Wookie
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Re: Master 128 - obscure video issue?

Post by Wookie » Sun Feb 21, 2016 8:15 pm

Well I've just copied Frogger from floppy to MMFS on my Master and then run it from MMFS and it works perfectly, sorry but atleast on my Master MMFS does not cause a problem, so I think we can rule out MMFS as being a factor, surely it must be some hardware/timing fault with jnbeeb's Master.
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Re: Master 128 - obscure video issue?

Post by jbnbeeb » Sat Feb 27, 2016 4:51 pm

Hi guys - thanks to everyone who's posted on the thread. RL (Real Life) got in the way for a few days so not had chance to follow up.

I've read through the recent posts - and as at least two people have tried Frogger on their real Masters and not encountered the "corruption" on the bottom of the screen per my Master - it seems reasonable to conclude the issue is my Master and not anything else.
I would try actually physically pulling out the hardware, rather than *UNPLUGing the ROM.
I'm pretty sure I tried this in my initial tests, but just to be sure, I did so again today and loaded the game from floppy and got same result. I can't get any other software to produce these symptoms but then I've not tried every piece of software out there on it..

So.. question for the hardware folks here:
what component(s) is most likely at fault? My guess would be 6845 or one of the 6522s given Rich TW' and Tricky's comments in the posts upthread.
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Re: Master 128 - obscure video issue?

Post by tricky » Sat Feb 27, 2016 5:11 pm

I will try to send you one with different timing, in case it is just that.

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Re: Master 128 - obscure video issue?

Post by 1024MAK » Sat Feb 27, 2016 5:21 pm

jbnbeeb wrote:I'm pretty sure I tried this in my initial tests, but just to be sure, I did so again today and loaded the game from floppy and got same result. I can't get any other software to produce these symptoms but then I've not tried every piece of software out there on it..

So.. question for the hardware folks here:
what component(s) is most likely at fault? My guess would be 6845 or one of the 6522s given Rich TW' and Tricky's comments in the posts upthread.
Very, very tricky to fault find, this. And being a Master, the chips are all soldered in, so "quick" chip swaps are not very practical :( .

What would be useful, is if you can try as many games as possible that drive a Beeb as close to the limit as possible (well, ones that will run on a Master) to see if we can work out if there is anything in common. Because at the moment, all we have to go on, is one game. We suspect it is timing, but it may also be a weak logic signal on one of the many buses that the Master has.

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Re: Master 128 - obscure video issue?

Post by jbnbeeb » Sat Feb 27, 2016 5:53 pm

What would be useful, is if you can try as many games as possible that drive a Beeb as close to the limit as possible
I've tried Elite (master enhanced), Revs (both split screen), Tricky's Phoenix (I think screen splits and hardware scrolling), Firetrack (though I'm not convinced STH is a fully working version as it doesn't seem to double buffer on Master like it should), Rocket Raid (hardware scrolling), Stryker's Run (Master enhanced) . They all seem to run fine. Can anyone think of other games or software which really pushes hardware?

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Re: Master 128 - obscure video issue?

Post by tricky » Sat Feb 27, 2016 7:09 pm

It's more software than hardware, but try Astro blaster.
Did you say you had issues with Phoenix?

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Re: Master 128 - obscure video issue?

Post by jbnbeeb » Sat Feb 27, 2016 7:19 pm

tricky wrote:It's more software than hardware, but try Astro blaster.
Did you say you had issues with Phoenix?
Hi - the last version of Phoenix on RS thread doesn't appear to work on real h/w on Beeb B or Master - but I tried the penultimate one and that was ok on real Beeb B and Master

Re Astroblaster - the last version seems to detect speech chip on Master and doesn't load (at least on my Master :) ).
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Re: Master 128 - obscure video issue?

Post by Wookie » Sat Feb 27, 2016 11:43 pm

jbnbeeb wrote:
tricky wrote:It's more software than hardware, but try Astro blaster.
Did you say you had issues with Phoenix?
Hi - the last version of Phoenix on RS thread doesn't appear to work on real h/w on Beeb B or Master - but I tried the penultimate one and that was ok on real Beeb B and Master

Re Astroblaster - the last version seems to detect speech chip on Master and doesn't load (at least on my Master :) ).
Just tried the latest versions of both these games on my Master.

Phoenix plays music but the screen is garbled so you can't play but it does seem to respond to key presses.

Astroblaster loads the menu just fine, says it's using SPEECH chip with 1 SWRAM bank, and speech snippits can be heard just fine but when you press RETURN to start the game it loads a couple of things from disc and then locks up.

So I wouldn't worry jnbeeb about what your seeing with these games on your Master as it looks like they don't play on any Master, no offense intended Tricky, I imagine your primary target is the Beeb rather than the Master anyway.
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Re: Master 128 - obscure video issue?

Post by tricky » Sun Feb 28, 2016 8:53 am

Thanks for the bug reports, I don't have a working Master, but try not to do anything that won't work on the master, I'll have a look soon-ish.

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Re: Master 128 - obscure video issue?

Post by tricky » Sun Feb 28, 2016 1:06 pm

Found the bugs with AstroBlaster, one was in my speech chip patched beeb-em and the other was in checking *FX &EB to detect the speech chip.
For more detail, take a look at http://www.retrosoftware.co.uk/forum/vi ... 7513#p7513.
If anyone can check this on speech and non-speech masters, that would be very helpful.
AstroBlaster.zip
fixed speech chip detection
(41.59 KiB) Downloaded 15 times

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Re: Master 128 - obscure video issue?

Post by jbnbeeb » Sun Feb 28, 2016 4:13 pm

Hi Tricky,
tried latest Astroblaster on my Master - detects SWRAM and loads game - but garbled/rolling screen.

On my BBC B, it detects 1 ram bank (though I think I have two) and plays ok- though the screen flashes/rolls very briefly (less than a second) and then rights itself. *edit - of course, my BBC B has speech chip fitted so may only need 1 swram*

Obviously in my case we could have another example of a game that my Master has an issue with but ok for everyone else.

Brief video of output from Master on this dropbox link
https://www.dropbox.com/s/lyjv098nceutj ... 6.mp4?dl=0
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Re: Master 128 - obscure video issue?

Post by Rich Talbot-Watkins » Sun Feb 28, 2016 4:50 pm

As I mentioned somewhere else upthread, the only difference I can think of with the Master is that entering the IRQ routine takes a cycle longer - so if there's particularly tight timing, the interrupt code might happen a moment too late (which could be crucial when setting CRTC registers). Might be worth checking that everything works OK on your real Beeb if you hack an extra cycle into the beginning of your IRQ handler.

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Re: Master 128 - obscure video issue?

Post by Wookie » Sun Feb 28, 2016 4:58 pm

jbnbeeb wrote:Hi Tricky,
tried latest Astroblaster on my Master - detects SWRAM and loads game - but garbled/rolling screen.

<SNIP>

Obviously in my case we could have another example of a game that my Master has an issue with but ok for everyone else.
Well I've just tried it on my Master and it appears to play fine now, well done Tricky.

Sorry to say this jnbeeb but it looks like another game your Master doesn't like, hmmm! Image
At least its another bit of code that for some reason doesn't run on your machine, it might just help narrow down your machines fault.
cheers Wookie
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Re: Master 128 - obscure video issue?

Post by CMcDougall » Sun Feb 28, 2016 5:40 pm

Your Dropbox vid, are you sure your M128 actually has a electron in it :? :lol:
One of my M128s does weird things too (but plays nothing) so, time to buy another for £25, make sure it works, and unsolder ever chip and swap, I've done 60% of mine, still same.... :cry:
viewtopic.php?f=3&t=8739&hilit=bbc+mast ... =30#p98060
so, when you find your fault, bets are it's similar to mine....
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Re: Master 128 - obscure video issue?

Post by tricky » Sun Feb 28, 2016 9:19 pm

With the extra delay displaying more pixel lines before changing the display address, it does look like there is something amiss with your 6845, but as long as it works for your game, I wouldn't worry.

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