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Will memory with higher strobe latency slow my system ?



 
 
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  #1  
Old September 24th 10, 03:36 AM posted to comp.sys.ibm.pc.hardware.chips
Dave WB3DWE
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Posts: 2
Default Will memory with higher strobe latency slow my system ?

Have Dell Precision 390 with 2 GB DDR2-532 ECC memory
in two modules, 266 MHz, CAS 4-4-4-12 per Memtest86+.
This is a strobe latency of 4 cycles.

Want to add two 1 GB modules to bring up to 4 GB. The
closest Crucial has is DDR2-667 with strobe latency
of 5 cycles.

According to a chart the current modules ( strobe latency
4 cycles ) have a strobe latency of 15 ns. The Crucial
modules with strobe latency 5 cycles would have latency
of 18.8 ns if run at current bus speed.

If these DDR2-667 modules run at the 5 cycle latency in
my 266 MHz ( DDR2-532 ) bus, my memory access will
be 25 % slower : (

Is this true ? Will the Crucial DDR2-667 modules revert
to a strobe latency of 4 cycles when run in my 266 MHz
(DDR2-532) bus ?

This is an old relatively slow system ( CPU 1.8 GHz ). Doubt
I can speed up the memory bus. Speed is more important
to me than 4 GB memory. Should I add the Crucial
modules ? Thanks, Dave WB3DWE
  #2  
Old September 24th 10, 09:15 PM posted to comp.sys.ibm.pc.hardware.chips
Yousuf Khan[_2_]
external usenet poster
 
Posts: 1,296
Default Will memory with higher strobe latency slow my system ?

On 23/09/2010 10:36 PM, Dave WB3DWE wrote:
Have Dell Precision 390 with 2 GB DDR2-532 ECC memory
in two modules, 266 MHz, CAS 4-4-4-12 per Memtest86+.
This is a strobe latency of 4 cycles.

Want to add two 1 GB modules to bring up to 4 GB. The
closest Crucial has is DDR2-667 with strobe latency
of 5 cycles.

According to a chart the current modules ( strobe latency
4 cycles ) have a strobe latency of 15 ns. The Crucial
modules with strobe latency 5 cycles would have latency
of 18.8 ns if run at current bus speed.


4 cycles/533 MHz = 7.5 ns. 5 cycles/667 MHz = 7.5 ns. It looks identical
to me. What's going to happen is that since 667 MHz memory is going to
be run at the slower speed of 533 MHz, it'll have a 4 cycle latency
instead of 5.

Yousuf Khan
 




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