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In an effort to better understand RAM, I am diving into specs and attempting to resolve displayed entries to understandable research results. So far, my research has not provided me with explanations I can use for JDEC entries. My basic specs are dual channel DDR3, 665 MHz, 9-9-9-24. I believe I understand this part. However, when expanding SPD and the included JDEC entries, I find the following:
JEDEC #5
Frequency 685.7 MHz
CAS# Latency 9.0
RAS# To CAS# 9
RAS# Precharge 9
tRAS 25
tRC 34
Voltage 1.500 V
JEDEC #4
Frequency 609.5 MHz
CAS# Latency 8.0
RAS# To CAS# 8
RAS# Precharge 8
tRAS 22
tRC 30
Voltage 1.500 V
JEDEC #3
Frequency 533.3 MHz
CAS# Latency 7.0
RAS# To CAS# 7
RAS# Precharge 7
tRAS 20
tRC 27
Voltage 1.500 V
JEDEC #2
Frequency 457.1 MHz
CAS# Latency 6.0
RAS# To CAS# 6
RAS# Precharge 6
tRAS 17
tRC 23
Voltage 1.500 V
JEDEC #1
Frequency 381.0 MHz
CAS# Latency 5.0
RAS# To CAS# 5
RAS# Precharge 5
tRAS 14
tRC 19
Voltage 1.500 V

The JDEC#5 timing matches the specs for the RAM I have installed. Each JDEC# lists different timing numbers. Note that the lower the JDEC#, the faster the speed. Why are the other JDEC#/timing numbers included? Does this indicate the ability to speed up my memory (overclocking)? I have no desire to overclock. This is just an academic exercise on my part.

Posted 1 year ago
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