Acorn ATOM - PAL to NTSC

discussion of games, software, hardware & emulators relating to the Acorn Atom
waltermixxx
Posts: 173
Joined: Wed Jan 14, 2015 4:18 pm
Location: Toronto

Acorn ATOM - PAL to NTSC

Postby waltermixxx » Tue Nov 28, 2017 12:55 am

Hi there, I was looking at the schematic for the Acorn Atom, and I was wondering,
would it possible to change the video output to NTSC by simply changing the frequency of the
3.58 MHZ crystal for the 6847? :) would there need to be changes to the MOS rom as well?
(speaking strictly about the regular Acorn Atom without the colour board.) For the life of me,
I cannot recall if I had a colour board for my Acorn Atom back in the day, as I would have been limited to
a small black and white tv. or monochrome monitor... I wish i could remember... :)


at any rate:
:) any North American Acorn Atom users around? :)

cheers. :)


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DutchAcorn
Posts: 1631
Joined: Fri Mar 21, 2014 9:56 am
Location: Maarn, Netherlands

Re: Acorn ATOM - PAL to NTSC

Postby DutchAcorn » Tue Nov 28, 2017 6:54 am

And another one, in colour (color :D )
Attachments
IMG_4192.JPG
Paul

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danielj
Posts: 5345
Joined: Thu Oct 02, 2008 4:51 pm
Location: Manchester

Re: Acorn ATOM - PAL to NTSC

Postby danielj » Tue Nov 28, 2017 7:18 am

Same modulator as in the ZX81, so this might help: http://zx81.republika.pl/ZX81_SCHEME.jpg
I think the 6847 is already pushing out a 60Hz display, the colour burst crystal is the right value for NTSC (not that there's any colour). Your best option is to take composite out if you have something that can deal with it?

d.

waltermixxx
Posts: 173
Joined: Wed Jan 14, 2015 4:18 pm
Location: Toronto

Re: Acorn ATOM - PAL to NTSC

Postby waltermixxx » Tue Nov 28, 2017 11:01 am

Thanks for your replies, I do have the schematic, I was just wondering if I would need to make any changes to an acorn atom for use on a regular ntsc LCD monitor. But I figure based on replies thus far, that I won't need to, as there is no chroma in the composite video output.

I hope I have that right.

Prime
Posts: 2345
Joined: Sun May 31, 2009 11:52 pm

Re: Acorn ATOM - PAL to NTSC

Postby Prime » Tue Nov 28, 2017 4:45 pm

Yep 6847 is natively NTSC, so you should be good to go.

Most of the computers that used it and output colour that where sold in PAL reigions hat to use various hacks to convert the signal, such as cutting the clock to the 6847 and using external logic to insert extra blank lines. The Atom just required you to have a monitor that would sync at 60Hz.

Cheers.

Phill.

waltermixxx
Posts: 173
Joined: Wed Jan 14, 2015 4:18 pm
Location: Toronto

Re: Acorn ATOM - PAL to NTSC

Postby waltermixxx » Tue Nov 28, 2017 6:20 pm

excellent, thanks everyone. :)


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