[SI-LIST] Re: DDR2 or DDR3
- From: "James Bell" <james.c.bell@xxxxxxxxxxx>
- To: "'Martin Euredjian'" <martin_05@xxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 22 Dec 2008 12:43:14 -0800
Martin,
If you are thinking about a trade off between DDR2 vs. DDR3 DIMMs, one
advantage DDR3 has over DDR2 is the on-DIMM terminated Address/Command and
Clock nets, which will take at least some of the SI burden off of you. The
down side is, if you intend to develop your own memory controller inside an
FPGA or ASIC, your memory controller internals become more complex for DDR3
because of the fly-by topology used for Address/Commend and Clock nets,
causing the data to/from the indivdual memory devices to be valid at
different times.
For memory down applications if you don't need the increased step up in data
rates DDR3 gives you I recommend sticking with DRR2 and it's tried and true
memory topologies and simpler controller state machine.
- Jim
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Martin Euredjian
Sent: Monday, December 22, 2008 10:49 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] DDR2 or DDR3
I am having to decide between DDR2 and DDR3 for a new design. Of course,
there really isn't much of a raw performance advantage in DDR3 (if operated
at the same clock rate as DDR2). The primary advantage seems to be in that
it is much easier to achieve timing goals because of the "divide and
conquer" capability of the technology. I don't think there are any SI
advantages.
I am wondering if I am missing something fundamental in my evaluation, hence
the post. Any thoughts on this?
Thank you,
-Martin
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