No, I don't need to do any research, I have a degree in computer science.
The magic word you don't seem to understand is
underclocked.
Seeing as you see Wikipedia as the font of all knowledge, here is a link:
http://en.wikipedia.org/wiki/Underclocking
As both my post and the article I linked to mentioned, the Pentium M chip in the original Apple TV is
underclocked.
From
http://en.wikipedia.org/wiki/Pentium_M It's clear that the low end 1Ghz chip has a FSB of 400Mhz.
From the article I linked to:
http://www.appleinsider.com/articles/07/01/15/pentium_m_based_intel_chip_at_heart_of_apple_tv.html
So if a chip is
underclocked from running on a 400Mhz bus to a 350Mhz bus, based on the multiplier, the clock speed of the Apple TV is
875Mhz.
And in case you need it spelt out for you, 875Mhz < 1000Mhz.