CS2610: Computer Organization and Architecture Lab Assignment #6

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Objective: To understand the internals of DRAM row-buffer management.

Questions:

1. Implement a Hybrid-Row-Buffer Management Policy, known as Adaptive-Page
Management Policy. The details of policy are explained below:

a. Use a 4-bit saturation counter, and choose two threshold values, namely,
High-Threshold and Low-Threshold, with a difference between them not
more than 6 and not less than 4.
b. Initially, set the counter to somewhere in the middle of the range between
high and low thresholds and start with Open-Page policy.
c. switch from Open-Page to Close-Page policy when the count is greater
than High-Threshold and increasing, and from Close-Page to Open-Page
policy when the count is less than Low-Threshold and decreasing.

d. If currently in Open-Page policy, and a page-hit is observed, no action to
be taken.
e. If currently in Open-Page policy, and a page-miss occurs, increment the
counter.

f. If currently in Close-Page policy, and if a page-hit with the last closed
page occurs, then decrement the counter.
g. If currently in Close-Page policy, and a page-miss occurs, no action to be
taken.

2. Compare the number of cycles (output) reported by USIMM for the all the traces
run with Open-Page, Close-Page, Adaptive-Page management policies. Report the
best policy.

3. Compare the DRAM performance (in cycles) for the two address mapping
schemes, provided in USIMM, for the best row buffer management policy
determined in previous part of the question.

Make a table containing performance reported in number of DRAM cycles (as
reported by simulator) for the above questions. Give a brief summary of the
implementation. Provide appropriate justifications (necessary).

Instructions:

• We use the USIMM simulator for this assignment.
• You can download the simulator (version 1.3) from here:
https://www.cs.utah.edu/~rajeev/jwac12/
• Instructions on how to get started are clearly mentioned in README file.
• To model a quad-core system and execute a benchmark in rate-mode on that
system, specify the same benchmark four times on the command line.

Ex: to execute ‘libq’ in rate mode on a quad-core system run the following
command:
bin/usimm input/4channel.cfg input/libq input/libq input/libq input/libq
• Use 4 channel configuration and 4Gb x8 devices for all the simulations (devices
can be specified in main.c).