[coreboot] building SPD: How to decide Trfc by spec

[David Hendricks]

Hi Zheng,
I believe that "-x GB" simply means that there are different Trfc values
for each size module.

Trfc is stored in MTB units, though. So you need to:
1. Convert nCK to nanoseconds
2. Convert nanoseconds to MTB units

For example, if you have a 1Gb module that is running at 800MHz, then Trfc
will be 88 clock cycles. 1sec / 800MHz = 1.25ns per cycle, therefore 88
cycles = 110ns.

Then you need to convert the total time into MTB units. So if your timebase
(SPD bytes 10 and 11) is 0.125, Trfc is 110 / 0.125 = 880. (This matches
the calculation shown for bytes 24 and 25 in the SPD spec:
http://www.jedec.org/standards-documents/results/Annex%20K%20SPD).


On Fri, Apr 1, 2016 at 5:30 PM, Zheng Bao <fishbaoz at hotmail.com> wrote:

>                             DDR3-1066 DDR3-1333 DDR3-1600   DDR3-1866
> unit
>                                  7-7-7           9-9-9        11-11-11
> 13-13-13
> nRFC-1 Gb                  59               74
> 88               103             nCK
> nRFC- 2 Gb                 86              107            128
>   150              nCK
> nRFC- 4 Gb                160             200            240
> 281              nCK
> nRFC- 8 Gb                187             234            280
> 328              nCK
>
> Hi, All,
> Above text is extracted from the spec of a DDR3 chip.
>
> I am trying to decide the Trfc.
> What does "-x Gb" mean? How do I know which row in the table I should use?
> Thanks.
>
> Zheng
>
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>
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