PC motherboards without a 14.31818 MHz crystal

[japlytic]

On an Asus P8Z68-M PRO motherboard from, I could not find a 14.31818 MHz crystal anywhere; all of the crystals except the RTC crystal were marked with MHz integers.
You may know this, but 14.31818 MHz was used in the original IBM PC (4.772766 MHz for the 5 MHz-rated CPU (divide by 3) and (on a video card) 3.579545 MHz for NTSC colourburst (divide by 4).
So therefore (in my theory), it is easier to generate required clock frequencies (including the 100 MHz reference clock for PCI Express) with a crystal of a MHz integer than a 14.31818 MHz crystal - are all new PC motherboards going this way?

[stj]

Re: PC motherboards without a 14.31818 MHz crystal

it's down to the PLL/clock generator they choose.

i'm surprised they arent trying to use the 32KHz crystal!

[RJARRRPCGP]

Re: PC motherboards without a 14.31818 MHz crystal

Looks like that's the standard HPET granularity frequency.

[mariushm]

Re: PC motherboards without a 14.31818 MHz crystal

It's been a long time since computers had to use weird clock frequencies to get other frequencies by division or multiplication.

Why would they use something chosen because it's ntsc subcarrier.. ntsc is not the only thing in the world.
See https://en.wikipedia.org/wiki/Crysta...or_frequencies for common frequencies.


You may still find some weird clocks for UART (serial ports) or on sound cards...

You're more likely to find 12 Mhz with USB

@RJARRRPCGP that varies, for example on my system it's 3.418 Mhz

[RJARRRPCGP]

Re: PC motherboards without a 14.31818 MHz crystal

It's been a long time since computers had to use weird clock frequencies to get other frequencies by division or multiplication.

Why would they use something chosen because it's ntsc subcarrier.. ntsc is not the only thing in the world.
See https://en.wikipedia.org/wiki/Crysta...or_frequencies for common frequencies.


You may still find some weird clocks for UART (serial ports) or on sound cards...

You're more likely to find 12 Mhz with USB

@RJARRRPCGP that varies, for example on my system it's 3.418 Mhz

I heard that the 3 Mhz one isn't HPET.

See this thread:

https://www.badcaps.net/forum/showthread.php?t=75378