Messages in this thread | | | Date | Thu, 17 Apr 2003 07:34:36 +0200 (CEST) | From | Peter Svensson <> | Subject | RE: my dual channel DDR 400 RAM won't work on any linux distro |
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On Wed, 16 Apr 2003, Robert White wrote:
> The BS layman's speak they gave me at the store was that they had seen a lot > of cases where having "double sided SIMMs" (they were oh-so-usefully > classifying the memory based on whether there were chips on just one side, > or on both sides of the circuit card 8-) in the second and subsequent slots > never worked.
This is actually a perfectly resonable thing to do. Twice the number of chips (and for double-sided modules with stacked chips four times) will load the address bus with twice (our four times) the capacitance. Thus the siganl flanks will become less and less well defined when adding more chips on the bus until some access patterns start to give bad results.
Some motherboards, mostly servers, specify registered memories that have a buffer circuit to greatly reduce the load on the line drivers. More serious technical details from at least some motherboards will specify that only a maximum number of chip-loads are possible. Since there are only a few address bus driver chipsets the same limitations apply to most motherboards. The manefacturer can play some games with voltages and buffer strentghs but only so much. At high speeds and several stacked-chip modules you really need registered modules.
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