Transcript On-Chip Networks and Testing

On-Chip Networks and
Testing-II
Ob-Chip Networks and Testing
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Aethereal NoC as
Communication Fabric for SoC
1.
2.
Goosens et al., “Aetherial Network on Chip ...,” IEEE D&T
Magazine, Sept-Oct 2005, 414-421.
Vermeulen et al., “Bringing Communication Networks on a Chip:
Test and Verification
Implications,” IEEE Communications Magazine, Sept. 2003, 74-81.
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Rationale for Aethereal
As SoC complexity grows, its communication
infrastructure is a major concern.
Expert opinion says NoCs are increasingly likely to be
the choice for on-chip communication because they
provide structure, modularity, and performance
advantages over alternative designs
Aethereal NoC is a research product from Philips to
explore NoC-based SoC designs.
Vermeulen et al. [2] consider an Aethereal-based SoC
design for multimedia applications and discuss how it
can be tested and verified.
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Example SoC with Aethereal NoC
The picture shows
routers, network
interfaces,
processor, memory,
and memoryinterface cores, and
neighbor-links.
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Combined Guaranteed- Throughput (GT)
and Best-Effort (BE) Router
Conceptual View
Hardware View
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Aethereal Chip: Contention-Free Routing
Contention-free routing: network of three routers (R1, R2, and R3)
at slot s = 2, with corresponding slot tables (T1, T2, and T3).
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Default Core-Based Testing
The default method
assumes the cores are
wrapped, according to
IEEE1500 and uses
dedicated TAMs to
transport test data.
The example shows
cores tested
simultaneously by 4
TAMs.
Disadvantage: Wire
congestion due to
TAMs.
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NoC Reuse Based Testing
NoC blocks (routers and
network interfaces) are tested
first (top).
If ok then NoC can be used to
help test other cores (bottom).
Further, because routers are
identical, their test data sets
can be broadcast and applied
concurrently and their
responses can be compared to
each other for mismatches (for
go/no-go testing)
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Reuse-Based Test Scheduling
1.
2.
C. Aktouf, “A Complete Strategy for Testing an On-Chip
Multiprocessor Architecture,” IEEE D&T, Jan-Feb 2002, 18-28.
C. Liu et al., “Reuse-Based Test Access and Integrated Test
Scheduling for NoC,” DATE’06, 303-308
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Complete Strategy Summary [1]
Homogeneous fine-grain, massively
parallel, message-passing,
multiprocessor in 2D topology
Testing in three phases:
Router Testing (by groups of cells)
2. RAM Block Testing (using BIST)
3. Distributed Processor Testing (using PMC
model)
1.
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Multiprocessor Architecture
Interconnection network
on top – shading shows
two cells communicating
using shared buffers.
Cell Structure at the
bottom. Each cell
consists of Processor,
Memory, and Router
Messages include
relative x and y
displacements, address,
and data.
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Boundary-Scan Based Testing of Routers
in Groups of Cells (GCs)
Basic-cell groups (top)
and test-circuit
configuration for
external test (right)
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Reuse-Based Test Access and Test
Scheduling [2]
Summary
2D mesh architecture similar to [1].
Each cell consists of a core and router.
Progressive reuse of network resources
for transporting test data
Routers and cores tested concurrently
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System Architecture
1x1 groups
2x2 groups
The top picture shows a 12node system in which a
particular SoC (ITC02
benchmark d695) has been
mapped to 10 available
nodes.
Two shaded cores are being
tested using dedicated paths
from external inputs to the
core an from the core to an
external output
The paper compares results
to those in [1] that uses the
GC approach (bottom) to
testing routers first.
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Progressive Scheduling for Router Testing
Multicast network
Unicast network
Constraint: Only pretested routers can be reused for test-data transport, hence
need for scheduling
Test responses are assumed to be processed on-chip or compressed and
transported off-chip through dedicated paths
The picture shows 2x2 I/O, numbers represent groups of cells that can be
tested simultaneously, in increasing order of group numbers.
Even though only 10 cells are occupied, for testing all 12 must be tested.
Only the router-under-test is in test mode, others on the path are in normal
mode.
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On-Chip Test Response Processing
Using MISRs
Using Comparators
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Integrated Test Scheduling
Consider the unicast network
scheduling example from
before:
Assume both bottom row
routers have been tested in
steps 1, 2, and 3.
We can reuse Input 2 and
Output 2 to test bottom-row
cores; at the same time we
can reuse Input1 and Output
1 to test routers in group 4.
The paper gives an algorithm
for scheduling such integrated
testing
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A Sample of Results
Col 2: Boundary-scan results from [1] assuming all routers are tested
simultaneously - only router testing times are shown
Col 3: router testing time when network is reused (Savings over Col 2)
Col 4: Test bus results from TAM co-optimization by Iyengar et al.
(DATE 2002) – discussed earlier.
Col 5: Routers and cores test separately
Col 6: Integrated testing (savings over Col 5)
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Conclusion
Testing research on NoC-based SoC is still in
infancy.
Approaches are highly dependent on
assumptions about the system and NoC
architectures, hence hard to compare against
each other.
ITRS projections, however, show that NoC is
likely to be the dominant communication
mechanism of the future SoC, hence this is
good field of research to get into.
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Bibliography
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Goosens et al., “Aetherial Network on Chip ...,” IEEE D&T
Magazine, Sept-Oct 2005, 414-421.
Vermeulen et al., “Bringing Communication Networks on a Chip:
Test and Verification Implications,” IEEE Communications
Magazine, Sept. 2003, 74-81.
C. Liu et al., “Reuse-Based Test Access and Integrated Test
Scheduling for NoC,” DATE’06, 303-308.
C. Aktouf, “A Complete Strategy for Testing an On-Chip
Multiprocessor Architecture,” IEEE D&T, Jan-Feb 2002, 18-28.
Nahvi and Ivanov, “A Packet Switching Communication-Based
TAM for SoC,” ETW01, 81-86.
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