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ddr sdram and performances

 

ddr sdram and performances

I am migrating a Sybase RDBMS from an rp3440 with 4 PA8800 1 GHz processors with 8 GB of (A9774A) DDR-SDRAM
to
a similarly 4 PA8800 1 GHz processors (A6437A)rp8420 cell, in this case with ( AB308A ) SDRAM.
Can I expect lower performances beacuse on non-DDR RAM (all the rest being almost equal)?
Thanks in advance,
Marco
2 REPLIES 2
rick jones
Honored Contributor

Re: ddr sdram and performances

I don't think that in and of itself DDR vs non-DDR would be the issue. You might want to compare basic memory latency between the two systems.

Even if one system has higher memory latency that may not result in lower performance. It depends on how many different memory accesses can be "in flight" at one time.

Also, it may be the case that the descriptions of some RAM aren't "complete" and something that may be "DDR" may not be labled as such.

Finally, it is my understanding there are some strong guidelines for memory configuration on the cell-based systems. I'd point you to them directly, but don't recall the URLs. It would be good to excercise the support contract and get some of the specifics.
there is no rest for the wicked yet the virtuous have no pillows
Khairy
Esteemed Contributor

Re: ddr sdram and performances

From the quick specs, the rp3440 open page memory latency is 80ns.

From the rp8420 quick specs, the memory latencies value are relatively higher between cells based on how many cells are configure for a partition. In your case, i think you're migrating to a partition with 1 single cell configured. I think it won't show much difference. But i would love to hear comments from you soon on the performance comparison between the 2 different server after the migration complete.

Rgds