Sierra M6
‐
2 SAS/SATA Protocol Analyzer User Manual
259
Sampling Memory Usage Optimization
LeCroy Corporation
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Sampling Memory Usage Optimization
The Software Settings dialog has a Sampling Memory Usage Optimization option. This
Memory Assignment (MA) feature optimizes sampling memory utilization.
If the Sampling Memory Usage Optimization Option is Checked
The system tries to use empty space in all memory banks to prevent any memory bank
from filling completely. Each physical link is not necessarily assigned to a specific memory
bank. The system can capture more sample data than if the MA option is unchecked, and
sample file size is closer to the user
‐
defined Sampling Memory Size.
Memory Assignment efficiency varies with Port Configuration and Trigger Position:
FPGA
: The Memory Assignment feature works for a pair of ports connected to
one FPGA, for example ports 1 and 2 (or ports 3 and 4). Memory Assignment
does not work for two ports connected to different FPGAs, for example ports 1
and 3.
Triggering
: Memory Assignment only starts after the trigger point. During
pre
‐
trigger, each physical link is always assigned to a specific memory bank.
Post
‐
trigger, the system can try to use empty space in all memory banks, if you
check the MA option. Therefore, Memory Assignment efficiency is maximum
when Trigger Position is set to 0% (snap
‐
shot trigger) and is minimum when Trig
‐
ger Position is set to 99% or when there is no triggering (you stop recording man
‐
ually).
MUX
: When MUX is enabled, each segment has four memory banks, limiting
Memory Assignment somewhat.
Here are examples of different Port Configurations and Trigger Positions:
One
port
configuration
(A
‐ ‐ ‐
):
Sample size is user
‐
specified sample size.
Two
port
configuration
(AA
‐ ‐
)
: Ports 1 and 2 are on the same FPGA, so
Memory Assignment has an effect. If you use snapshot triggering, the sample
size is near specified size.
Two
port
configuration
(AA
‐ ‐
):
If you use manual stop, Memory Assignment has
no effect. Sample size depends on port traffic loads.
Two
port
configuration
(AA
‐ ‐
)
: If trigger is set at 50%, and there is enough data
to fill pre
‐
trigger, Memory Assignment has an effect. Sample size is typically near
specified size.
Two
port
configuration
(AA
‐ ‐
)
: If trigger is set at 50%, but there is not enough
data to fill pre
‐
trigger, Memory Assignment has an effect. Sample size is typically
more than half specified size, with size determined by the amount of data cap
‐
tured before trigger.
Two
port
configuration
(A
‐
A
‐
)
: Ports 1 and 3 are not on the same FPGA, so
Memory Assignment has no effect. If one port has heavy traffic, it may fill its
memory bank and stop recording, resulting in smaller sample size than specified.
