NTSC MiniMig

[alexh]

1) If MiniMig doesnt do NTSC timings, then it wont work on American TV's. This point is a little moot because V1.0 of the PCB has no video encoder only RGB output and with no RGB TV's in the USA it doesnt matter anyhow.

2) Most PC LCD monitors will not function below 56Hz which means unless the PAL version of MiniMig can be made to do 60Hz it wont work on PC VGA LCD monitors.

[persia]

Nonsense I have an Aussie DVD player (PAL) hooked up to an American TV (from Costco) and it works fine.

[Hans_]

persia wrote:
Given that all televisions and monitors available nowadays are by default multisystem does this matter?  In the old days mutisystem tubes were complicated, but who needs (or wants) some boat anchor with a tube in it?

Some games were NTSC only, others were PAL only. PAL screens have slightly higher vertical resolution than NTSC. If you want to play games they way that they were originally indended, supporting both is best.

Hans

[Hans_]

narmi wrote:
A RGB to S-Video/composite encoder onboard could also be added, like the one I posted on the EAB.  It can do both NTSC and PAL.

That's a good idea. S-Video gives much better quality than composite. Having both expands options.

@Piru

So extending MiniMig to the ECS chipset is what's required. Any hardware changes that you can think of? It sounds like this could be added with just Verilog code.

Hans

[Dennis]

have to say that I am not 100% upto speed on the guts of either the Amiga hardware OR MiniMig but I thought that I would have a go and perhaps Dennis would read and help correct a few things.

You're quite right.  :-)
the mclk has to be changed to the NTSC color frequency (and the DCM reprogrammed) and you'll have to make the frames shorter by changing the verbeam compares. But, if I look in the hardware reference manual (page 18, copper), it states that on NTSC machines, the horizontal lines are not all 227 color clocks long. (on Minimig that means 454 bus clocks) Every other line is a long line (228 clocks) from the system's point of view. The display/tv however sees only 227.5 clock lines. So, you will have to do some stuff with the horbeam compares and horizontal sync generator too. That should be all though.

Dennis

[Dennis]

If the only physical change is to swap the crystal. Maybe a change should be incorperated such that both clock sources (pal=4.433619 ntsc=3.579545) are available to the fpga..?

It should be possible to generate both clocks from a single 20Mhz or 50Mhz source. (20Mhz would be better) Someone on the old minimig thread suggested a possible setting of the DCM to do just that; generate all PAL clocks from a single 50Mhz clock using the DCM. If I recall, he was only a couple of ppm off, which should be good enough. You could de the same for NTSC, hence all could be done in software/verilog.

Dennis

[freqmax]

I have created a Minimig wiki:
http://www.opencircuits.com/Minimig_NTSC - NTSC Issues
http://www.opencircuits.com/Minimig_Project

My hope is that it will help people to accumulate knowledge in this matter such that one doesn't have to read long.. threads to find information.
Especially now that there are several.

No login required, works almost like wikipedia.

[Piru]

@freqmax

So does this mean I can remove the obviously wrong quote from alexh? (about system running at different speed when you toggle between PAL/NTSC display modes.. Amiga bus clock does NOT change, nor the CPU clock)

Some music players run at different speed because they're timed to the vertical blanking frequency, and not CIA timers (vertical blank rate is 50Hz for PAL and 60Hz for NTSC, CIA timer speed remains the same regardless of the display mode. PAL and NTSC systems do have different system base clocks and thus different CIA clocks. The system base clock - and thus the CIA base clock - do not change depending on the screenmode). The only speed gain in 3D games from NTSC is the smaller area to render.

*edit*

Now that I think about it, what MiniMig probably wants is the full deal: Changing the base clock aswell (that is really change between PAL and NTSC, not just the display mode). However, this cannot be done runtime (restart is needed).

[JosephC]

All that is needed is a Fat Agnus (ECS AGNUS).

All ECS A500s and A600s can switch between PAL and NTSC at will.  Any program can flip a single bit to flip from one to the other.

So just implement ECS Agnus in the FPGA and all your problems are gone.

[little]

@piru

Changing the base clock by restarting can also be useful for overclocking the minimig, if I remember correctly 28mhz is achivable with a real 68000 and 14mhz with a software core.

[Crom00]

Don't have a Mini-MIG to test on US LCD/CRT monitors yet. Will advise further once I get ours finished and can execute some tests.

Anyone out there with the expertise to revise the current Mini-MIG spec to a NTSC/PAL switchable version?

[JosephC]

My first OCS A500 from 1987 was permanently stuck in NTSC mode.  Then one day in late 1988 or 1989 A500s started quietly shipping with "Fat Agnus" chips.  Soon afterwards, the Fat Agnus chips went on sale separately and you could put out your old Crap Agnus and replace it with the new Fat Agnus.  Then your Amiga suddenly became able to boot into either PAL or NTSC or even to switch in real time while running.

I used to switch out Agnusi back in the day for lots of friends.

So we just need to switch out the lame OCS Agnus in the Minimig with a shiny new ECS Agnus.

  And while you are at it, go ahead and make it a SuperFat Agnus(tm) that can address 8 MB of chipram so the tremendously expensive cost of the minimig might be justified.

Problem solved.

[little]

JosephC wrote:
And while you are at it, go ahead and make it a SuperFat Agnus(tm)

Super Fat Agnus is the name given to the 2MB non aga Agnus. I think Ultra Fat Agnus is in order for an 8mb version :-D

[little]

persia wrote:
Nonsense I have an Aussie DVD player (PAL) hooked up to an American TV (from Costco) and it works fine.

NTSC tv sets built five years ago or newer can display PAL signals, but that does not mean that all NTSC tv sets can display PAL, quite the opposite.

[leirbag28]

@piru


I am 1000% sure that games DEFINITELY run faster in NTSC mode............Positive! not just 3D games............platformers too.

Or perhaps its not that its running faster but normal.............and just slows down in PAL mode. Nevertheless the games run faster in speed in NTSC mode............sometimes too fast that the screen gets corrupted...............for intance Project X if run on NTSC on an A600 runs faster but gets all corrupted............take it to an A4000 and it can handle the speed upgrade and runs fine in NTSC mode but faster and smoother. ITs as if a heavy burden is lifted when the extra lines in PAL are eliminated when you put it in NTSC mode.

Same with LionHeart.   However games that were intended for PAL run better in PAL than NTSC even though the NTSC one is faster but gets corrupted.  Batman the Movie aslo runs faster in NTSC as well as GODS.

My guess however that this is only on an NTSC machine. If you ran PAL version of GODS on a PAL machine and an NTSC version of GODS on an NTSC machine, both would run the same and the music would be the same as intended by the authors.

I usually try to run my games in NTSC because I am in USA and because it runs faster.

[alexh]

Piru wrote:
So does this mean I can remove the obviously wrong quote from alexh? (about system running at different speed when you toggle between PAL/NTSC display modes.. Amiga bus clock does NOT change, nor the CPU clock)

From what I can tell, and what Dennis has said yes. A PAL Amiga running in NTSC mode doesnt change the bus clock speed.

Some music players run at different speed because they're timed to the vertical blanking frequency, and not CIA timers (vertical blank rate is 50Hz for PAL and 60Hz for NTSC, CIA timer speed remains the same regardless of the display mode.

That's what I concluded. There are fewer lines and a faster frequency and hence a shorter VBL period.

PAL and NTSC systems do have different system base clocks and thus different CIA clocks. The system base clock - and thus the CIA base clock - do not change depending on the screenmode). The only speed gain in 3D games from NTSC is the smaller area to render.

Yes. I think a true NTSC Amiga will have a faster bus/CPU clock than it's PAL rival, but it is so small, would it have  made a difference? The Atari ST people always used to shout about their 8MHz vs our 7.09MHz (PAL)

Now that I think about it, what MiniMig probably wants is the full deal: Changing the base clock aswell (that is really change between PAL and NTSC, not just the display mode). However, this cannot be done runtime (restart is needed).

Maybe, but I would imagine an ECS PAL Amiga at 60Hz to be more compatible than an NTSC Amiga at 60Hz? But there may be nothing in it.