[Pc_Support] Re: Great, budget, 'Best Practices' box

[Bryan J. Smith]

On Thu, 2006-07-06 at 15:40 -0500, David Simmons wrote:
> With the upper limit only being 400 MHz DDR2 (PC2-3200, right?)

There is no "upper-limit" to DDR or DDR2.  Signaling is signaling.
Timing is, of course, a larger issue.

However, the JEDEC standards only go to 200MHz DDR (DDR400/PC3200
effective) and 400MHz DDR2 (DDR2-800/PC2-6400), respectively.  There
might be a higher JEDEC DDR standard than 200MHz DDR, I haven't kept up.

Using non-JEDEC standard DIMMs is a good way to see incompatibility.

> - is there a chance this won't have some of the memory/chipset
> issues

Memory/chipset issues are the _result_ of _non_ JEDEC compliance.
There are a _lot_ of Intel _proprietary_ DDR2 SDRAM modules out there.
They are JEDEC standard to _only_ DDR2 266MHz (DDR2-533/PC2-4200), and
then they only work with the i945/955 for DDR2 333MHz
(DDR2-677/PC2-5300) and i965 for (DDR2-800/PC2-6400).

> (NewEgg reviews list how some of the AM2 boards say they can do 800Mhz

Yes, the Socket-AM2 supports JEDEC specification DDR2 400MHz
(DDR2-800/PC-6400).  Of course, if you get a DDR2 module that only
supports JEDEC to DDR2 266MHz (DDR2-533), then any speed above that is
_proprietary_ or non-standard.

> - but practically max out at 533 for single processor AM2's?!?)?

No.  JEDEC standards are everything to compatible.

A lot of existing DDR2 only supports JEDEC DDR2 200,266MHz
(DDR2-400,533/PC2-3200/4200).  They don't support the newer JEDEC DDR2
333,400MHz (DDR2-667,800/PC2-5300/6400) standards -- of which, they may
still not be final (is DDR2-800/PC2-6400 still draft?).


-- 
Bryan J. Smith           Professional, technical annoyance
mailto:b.j.smith at ieee.org     http://thebs413.blogspot.com
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