[LinuxBIOS] DIMM Page Size

Myles Watson myles at pel.cs.byu.edu
Wed Jul 11 16:50:22 CEST 2007



> Quoting Segher Boessenkool <segher at kernel.crashing.org>:
> 
> >> Anyone know what the mathmatical calculation is to determine a Dimms
> >> "Page Size"?? I found this but it does not seem to work:
> >>
> >> Page size = (2^col)*bus_width
> >> where,
> >> col = number of column address lines (SPD byte 4: Number of Column
> >> Addresses)
> >> bus_width = number of data(DQ) lines (???SPD byte 13: SDRAM Device
> Width???)
> >
> > "device width" is the number of data lines per DRAM chip on
> > your DIMM.  This isn't the same as the number of data lines
> > on the DIMM itself; that is 64 usually (not counting the ECC
> > bits).  This info is in the SPD as well.
> >
> >
> > Segher
> 
> Ok, so that must be byte 6: Data Width of Assembly.
> It still does not seem to compute though.
> 
> col = 9 /* SPD byte 4: Number of Column Addresses */
> bus_width = 64 /* SPD byte 6: Data Width of Assembly */
> 
> page_size = (2^col)*bus_width

2^9 = 512

> 5184 = 81 * 64

512 * 64 = 32K

Myles 

> 
> Which is not correct because the DIMM has a 4k page size.
> (According to it's datasheet).
> 
> Please Help.
> 






More information about the coreboot mailing list