[olug] [non-Linux] RAM hardware compatibility...

[Phil Brutsche]

Daniel Linder wrote:
> Are there any good, consise FAQ links that people can post that lay 
> out how the PC2100/2700/3200 relate to the front side bus

PC 1600:
   * 200MHz DDR
   * 100MHz base clock (DDR = double data rate at a certain clock speed)
   * AMD: 200MHz FSB
     Intel P4 + derivatives: 400MHz FSB
PC 2100:
   * 266MHz DDR
   * 133MHz base clock
   * AMD: 266MHz FSB
     Intel P4 + derivatives: 533MHz FSB
PC 2700:
   * 333MHz DDR
   * 166MHz base clock
   * AMD: 333MHz FSB
     Intel P4 + derivatives: mostly skipped this FSB speed, although
     I hear there are some 667MHz FSB Xeons coming
PC 3200:
   * 400MHz DDR
   * 200MHz base clock
   * AMD: 333MHz FSB
     Intel P4 + derivatives: 800Mhz FSB

> how the Intel/AMD marketing MHz numbers relate to FSB also?

A P4 with a 533 FSB will need PC 2100 or faster.  Intel FSB is 2x the 
memory DDR rate, or 4x the memory clock rate; Intel calls it a 
"quad-pumped memory bus".  It's also why P4s & derivatives see such a 
huge performance boost from dual-channel memory compared to Athlon XPs.

Athlon XP systems (and derivatives, like the Duron and Sempron <= 3000+)
are kept in step -> Athlon XP with 333MHz FSB needs PC 2700 (aka DDR
333) or faster.

Remember that Opteron-based systems (and derivatives, like the Sempron
3100+ and Athlon 64) do *not* have an FSB.  I do not know which Opterons
require which level of DDR, but I do know that it is somehow keyed off 
the HyperTransport clock speed.

You should keep in mind that even though a system has a 200MHz or 400MHz
FSB (aka PC1600, for a Duron or Celeron, respectively), memory rated for 
higher speeds will frequenly work just fine.  New P4 desktops from a 
"Tier 1" manfucaturer (I have direct experience with Dell and IBM in 
that category) will frequently ship with PC 2700, even though the CPU 
runs with a 400MHz or 533MHz FSB.

> How does "un-buffered" relate to "registered" if at all, and will
> they work in the motherboard?

Have you visited Crucial's (http://www.crucial.com) recently?  Crucial
is the factory outlet for Micron, they have a real nifty memory selector
that will tell you what kind of memory your motherboard will support,
and they have a pretty informative FAQ section.

Did I mention that Crucial sells high-quality memory at good prices? [0]

In particular, I think these pages are relevant to your questions:

http://www.crucial.com/kb/answer.asp?qid=4003
http://www.crucial.com/kb/answer.asp?qid=3682
http://www.crucial.com/kb/KBSearch.asp?SearchTerm=registered&Category=&go=go

[0] No, I don't work for Crucial, but I have purchased several dozen
gigabytes of memory from them over the last 2 years.

-- 

Phil Brutsche
phil at brutsche.us