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Amiga frequencies in NTSC
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Topic: Amiga frequencies in NTSC (Read 1596 times)
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Daff
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Join Date: Apr 2003
Posts: 214
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Amiga frequencies in NTSC
«
on:
October 22, 2012, 07:37:37 PM »
Hello,
When reading different articles and docs about the Amiga 500/600/CDTV, etc. we can see there are two different frequencies for the 68000 in NTSC Amiga models : 7,14 MHz and 7,16 MHz (7,15909).
The master clock in NTSC models is 28,63636 MHz which is divided by 4 : so we have 7,15909 MHz for the 68000 processor.
But a lot of articles say it's 7,14 MHz :
http://amiga.resource.cx/mod/a600.html
http://amiga.resource.cx/mod/a500.html
http://fr.wikipedia.org/wiki/Amiga_500
http://www.amiga-resistance.info/bboahfaq/index.php?sid=444372&lang=de&action=artikel&cat=7&id=1865&artlang=de
http://www.amiga-resistance.info/bboahfaq/index.php?sid=444372&lang=de&action=artikel&cat=7&id=1870&artlang=de
http://www.amiga-resistance.info/bboahfaq/index.php?action=artikel&cat=7&id=1863&artlang=de
etc.
Some says it's 7,16 MHz
http://en.wikipedia.org/wiki/Amiga_500
http://en.wikipedia.org/wiki/Amiga_1000
Even some articles says it's both :
http://www.amiga-resistance.info/bboahfaq/index.php?action=artikel&cat=7&id=1845&artlang=de
So my question is : which frequency is the good one ?
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amiman99
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Re: Amiga frequencies in NTSC
«
Reply #1 on:
October 22, 2012, 08:00:28 PM »
The Wikipedia looks more correct, because is specific on exact frequency and then the frequency is shorten to 2 decimal places.
I could take my frequency counter and measure the exact frequency to be 100% correct
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A500 KS 2.1, 1MB Chip, 68000
A600 KS 3.1, 2MB Chip, ACA630 32MB RAM
A1000 KS 1.3, 8MB RAM
A1200 KS 3.1, Blizzard IV 50MHz 64MB RAM
A2000 KS 2.1, 68030 25MHz, 6MB RAM
A3000 KS 3.1, 68030 25MHz, 16MB RAM
A4000 KS 3.0, 68040 25MHz, 16MB RAM
CDTV KS 3.1, 4MB RAM
CD32
(AROS BOX) Dead
Zac67
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Join Date: Nov 2004
Posts: 2890
Re: Amiga frequencies in NTSC
«
Reply #2 on:
October 22, 2012, 08:19:28 PM »
The schematics show precisely 28.63636 MHz for NTSC and 28.37516 MHz for PAL:
and everything else is derived from that (except for asynchronous accelerators).
btw: the oscillators have their frequency printed on them
«
Last Edit: October 22, 2012, 08:21:35 PM by Zac67
»
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