>> Speaking of which, even though the 80386 processor was introduced
>> in 1985 (that's almost 30 years ago), PCs still boot up in 16-bit
>> mode. Yes, even the new 64-bit ones.
>
> Not all of them. Look up UEFI and coreboot.

As Warp says, this is a function of the CPU, not the OS or the BIOS or 
anything else. It's in Intel and AMD's reference manuals. (Although I 
haven't looked into 64-bit; maybe it starts in a less-ancient emulation 
mode?)

> I thought the 64-bit mode was exactly the same as the 32-bit one, except
> that some memory pages are flagged differently?

No. In "long mode" (i.e., 64-bit mode) there are several brand new CPU 
registers available. It doesn't just make the existing ones wider. This 
means that code which is very register-heavy should hypothetically run 
faster, since you can hold more stuff in registers rather than on the 
stack or the heap.

IIRC, POV-Ray runs about 6% faster in long mode, indicating that 
actually the L1 cache makes the difference pretty damned moot anyway. 
(Contrary to my expectations.)

Post a reply to this message