| 1: |
What is the difference between the OCP and standard bus
specifications? |
| A: |
There are fundamental differences between the OCP and standard
bus specifications. OCP is viewed as a socket, and not as a bus
specification. In addition, OCP would normally be used on-chip, while
a bus specification (like PCI) can be used either on-chip or
off-chip. A white paper called "The Importance of Sockets in SoC
Design" on the OCP-IP Web site at www.ocpip.org
compares OCP to standard bus specifications. |
|
| 2: |
Is there an existing interconnection topology specifically
targeted to the OCP (to bus, hierarchical, crossbar, etc.)? |
| A: |
The first instance of a fully OCP compliant micro-network was
developed by Sonics, Inc. Their SMART Interconnect is but one example
of the family of solutions that could be developed to use OCP to
interconnect cores on an on-chip network or micro-network. A whole
new class of interconnect schemes has rapidly grown that can use OCP;
this is generally referred to as network-on-chip (NoC). There are
many references to such new work in the OCP-IP research bibliography,
which can be found at www.ocpip.org. Other
manufacturers have emerged with solutions (such as Arteris) and
indeed even traditional bus-interconnect schemes can be made OCP
compliant (such as work done by ST on its STBus). |
|
| 3: |
Are there timing or power models of the OCP modules? |
| A: |
There is a timing model specified in the OCP Specification. It
identifies three distinct levels of timing and spells out the per
signal timing requirements for the ASIC designer. The timing
requirements can be easily represented in synthesis and timing
scripts. The three levels are distinguished from each other by
performance and compatibility. Again, please see the OCP
specification for more details. Since the implementation of OCP is
highly design dependent, whether it is used natively and depends on a
proprietary protocol, or is simply bridged from an existing standard
bus like AHB or VCI, the power of the circuit is difficult to
predict. However, due to its highly configurable nature, a designer
need only use the features of OCP that are absolutely necessary for
that particular core's needs, therefore a native circuit can be
minimalistically developed thus creating a power efficient solution.
Existing bridges for many standard busses use a low number of gates,
from several hundred gates to the low thousands. |
|
| 4: |
Is OCP-IP the same as Opencores? |
| A: |
OCP-IP and Opencores are totally separate organizations.
Opencores is a truly open source provider, not a trade organization.
The protocol Opencores base their IP components around is called
Wishbone, which is a much simpler and older protocol generally used
in academic environments, less demanding of more sophisticated
requirements in complex SoC design. |
|
| 5: |
How does OCP-IP compare to VSIA? |
| A: |
Note: VSIA closed its doors effective CY08.
VSIA adopted a broad industry challenge to help its member
companies address the challenges of SoC design on multiple levels.
They operated through a broad range of working groups addressing such
issues as system-level design, analog mixed signal, test, quality, IP
protection, etc. Their charter was broad in nature, resulting in the
publication of important specifications, white papers and standards.
VSIA was not focused in providing the in-depth support and services
required to directly assist users of their specifications. The
charters and focus of VSIA and OCP-IP are quite different. To assist
VSIA members who are interested in OCP, the VCI standard permits the
use of veneers for direct conversion to the OCP standard, enabling
access to OCP-IP's tools and services so important to the use and
adoption of standards. As a further step in consolidating industry
behavior, VSIA endorsed OCP as the socket of choice in October
2003. |
|
| 6: |
What is the difference between OCP and the VSIA's
VCI? |
| A: |
OCP and VCI are quite similar in capability and in philosophy.
Both are socket specifications. However, OCP is a well-adopted,
comprehensive and supported standard. It is a superset of VCI. In
addition to data flow, OCP handles control and test flows. OCP-IP
provides not only the specification and its member-driven evolution
but also industrial grade tools and services that ensure members can
rapidly confirm compliance and maximize their productivity. |
|
| 7: |
Is OCP really a superset of the AVCI? |
| A: |
AVCI has some advanced features that have not yet been tested in
silicon or verified in any form. A specification alone is generally
not sufficient to make a standard both easy and compelling to adopt.
Companies investing in a standard require that it not only be
comprehensive, fully-defined, extensible and uniformly applied (as
enforced by a certification program), but also that there be
available products and services that support the standard; such
enhancements and support must also be predictably available into the
future. OCP 2.1 is already a functional superset of all essential VCI
features. |
|
| 8: |
Does OCP-IP offer a simple bridge for BVCI to OCP like its one
for PVCI to OCP? |
| A: |
There are some additional issues around the handling of bursts
that affect the BVCI bridge. However, with the 2.0 (and later)
release version of the OCP specification, which includes changes to
the burst specification in the OCP standard, it is quite simple to
build a BVCI bridge. |
|
| 9: |
What are the differences and what are the advantages OCP has
over AMBA? |
| A: |
First of all, OCP is a socket, while AMBA is a bus interface. A
socket is universal and is targeted for use in virtually any
application, while a bus interface (such as AMBA) is targeted at a
single unique application, where all of the arbitration logic and
interface circuitry is defined for that particular application.
Consequently, when the application design changes, then all of this
arbitration logic and interface circuitry needs to be taken apart and
re-designed for the new application. By contrast, a socket can be
targeted for any given application and moreover, this process can be
automated. The real benefit is that this socket-based IP block need
never be touched to be reused in multiple application designs. This
of course, greatly promotes design reuse and also aids the
verification problem. |
|
| 10: |
Does OCP-IP provide a design reference for APB and AHB
busses? |
| A: |
We are looking into the possibility of providing a reference
design.
|
|
| 11: |
Does OCP-IP offer any core code for PCI-X? |
| A: |
At this time, one for PCI-X has not been assigned. However,
please note that this listing of core codes is not part of the
specification per se but rather assignments that are handled as a
service by the OCP-IP organization. |
|
| 12: |
PCI supports dual address which means bigger than 32-bit, but
OCP only supports up to 32-bit address. Is there any
workaround? |
| A: |
At this point in time, this would be a limitation in the current
OCP specification. However, newer versions of the OCP specification
could be changed to support more than 32-bit addresses. Again, this
is not an inherent limitation of the OCP specification. |
|
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