SZ use CPU at 667 MHz FSB at 533 MHz. How?

How do Sony manage to run their SZ series notebook at 533 MHz Front Side Bus while the Core 2 Duo CPU that comes with the system use 667 MHz Front Side Bus?

 

If it's the sony SZ2XX series, then thats 533mhz because it runs core duo, not core 2 duo

 

This is actually SZ3xx series. So, it is Core 2 Duo. I still don't know how they could run FSB at 533 and manage to get the same overall clock speed. In order to do that, Sony has to modify the Clock Multiplier but the Clock Multiplier of the CPU is fixed.

 

The FSB supported by the CPU is fully utilized at 166MHz (quad-pumped effective speed of 667MHz), but they've used a locked FSB : DRAM ratio of 5:8 to have the memory run at 266MHz (or 533MHz effective speed).

 

So, a system that fully utilizes the CPU would have 1:1 FSB to DRAM ratio? How did you get 5:8?

 

As I've said earlier, the effective FSB speed is 667. Divide that by 4 since it is quad pumped on Intel chipsets and then you'll have the actual bus speed, 166MHz. Since we know the memory frequency is locked at 266MHz or 533MHz effective on Napa SZs, we know the ratio equals 166:266 or 5:8, and this ratio is how Sony can limit the frequency of the RAM, not the FSB. They can also limit the RAM frequency by explicitly setting it to 266MHz. I don't know which method they use, though, since the setting is not shown in the BIOS or in Phoenix BIOS Editor.