[coreboot] AMD Family 0Fh CAR and L1 cache tags

[Carl-Daniel Hailfinger]

On 15.01.2008 20:36, Rudolf Marek wrote:
> I just can explain in general what addresses are "forbidden".
>
> L1 cache is 64KB 2-way associative with 64B block size.
>
> This means 6 bits for data (to address the 64Bytes) and for the cache
> index we
> have 65536 / (  2 * 64) = 512 rows so we have 9 bits for this, rest is
> TAG.
> So the 32 bit memory address would look like this when cut:
>
> 31st ..... TAG ..... 14th  .... INDEX ..... 5th block addr.
>
> So "forbidden" addresses are all from range which will hit first 256 cache
> lines, so address from bit 0 to bit INDEX - 1 (13rd bit)
>
>  (X means dontcare 4 bits, x is dontcare one bit)
>
> xxxx x000 0000 00xx xxxx to xxxx x011 1111 11xx xxxx
>
> Which for it turns out anything in the address range XXXX0000 -
> XXXX3FFF will
> hit first 256 cache lines. Marc suggest that this is SW issue and not
> a HW issue
> so perhaps we can ignore this ;) but anyway, it is always good to
> explain why
> this addresses - I hope there is no mistake in my calculations.

Great explanation, thanks! Something like this should appear in the BKDG.

Regards,
Carl-Daniel