[LinuxBIOS] DIMM Page Size

Joseph Smith joe at smittys.pointclark.net
Wed Jul 11 15:41:00 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

5184 = 81 * 64

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

Please Help.

Thanks - Joe

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