Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
Paul wrote:
> In article <yzPUd.13628$LN5.459@edtnps90>, Xanophile <xanophile@gmail.com>
> wrote:
>
>
>>A friend gave me an old motherboard (K7M) with a 500MHz Athlon CPU. I
>>haven't had an issue with the motherboard except where the ram is concerned.
>>
>>All I have to put in it is all single sided dimms. 128's and 256's.
>>But it will only recognize half of any of them.
>>
>>Is double sided the only kind of ram this board can use or could this be
>>a symptom of something else?
>
>
> AMD751 Northbridge datasheet - page 66 covers the memory controller.
>
http://cdrom.amd.com/21860/21910.pdf
>
> In the table on page 66, the third from the bottom row of the
> table, is the key to making 128MB and 256MB unbuffered modules.
> (The row above it, would allow a 512MB module to be constructed,
> but it would have 32 chips, and would fry the memory controller,
> and as an unbuffered module, such a design is not viable.)
>
> 8-Bit Wide Device (Four Banks x 4 Mbits) = 16Mbit x 8
> 8 devices
> 128 Mbytes total
> Bank address bits = 2//MA12-13
> Rows = 12 address bits
> Columns = 10 address bits
>
> Here is an example of the right kind of memory chip. In the
> column labelled "16Mx8", you can see it has 12 row bits and
> 10 column bits.
>
http://download.micron.com/pdf/datasheets/dram/sdram/128MSDRAM.pdf
>
> Here is a properly constructed 256MB DIMM for K7M. Found via
> the www.kingston.com search engine for RAM for motherboards.
> Uses (16) 16Mx8 chips for 256MB. Would use (8) 16Mx8 chips
> if it was only a single sided 128MB module. In other words,
> to make a 256MB module that works, it has to be double sided.
> A 128MB module can be single sided, if the chips are 16Mx8 chips.
> (As I understand it, the reason Kingston dispenses PC100 for
> this application, is there is some kind of timing difference
> between the chips. At least I think that is why they do that.
> I don't think it has to do with the logical dimensions of the
> chips.)
>
>
http://www.valueram.com/datasheets/KVR100X64C2_256.pdf
>
> I realize this doesn't help you too much, except to note that
> if you looked up information about the memory chips (by using the
> numbers and letters on the chips), you could get enough info
> to determine whether the modules are addressable by that
> Northbridge.
>
> This is typically referred to, in postings to this group,
> as the difference between "high density" and "low density"
> RAM. If you look up info on the chips, then you have a
> better chance of understanding whether the right chips are
> on the modules or not.
>
> HTH,
> Paul
That's a whole lot of reading, but the gist of it, I get. Something to
pay attnetion to. Thanks.
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