高通的snapdragon和cortexA8的对比
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高通：
128b SIMD
两条定点流水10/12stages
一条load store流水线13stages
一条23stages浮点流水
流水线VFPv3
1Ghz for TSMC 65LP
200mW of 600Mhz
ARM Cortex A8：
64b SIMD
非流水VFPv3
1Ghz for TSMC 65GP
650Mhz for TSMC 65LP
350mW of 600Mhz
TI用了45个工程师一年时间进行OMAP3系列里面的cortexA8的layout
Qualcomm Reveals Details on Scorpion Core
By BDTI, 11/14/2007
Back in 2005, Qualcomm announced that it had licensed the ARMv7 instruction
set architecture and was working with ARM to create its own high-performance
core based on that architecture. The new core was dubbed “Scorpion,” and
at the time it was announced, Qualcomm didn’t disclose much about it except
that it would run at 1 GHz in a 65 nm process and would be customized to pr
ovide a high level of performance and energy efficiency in its target mobile
applications. Exactly how this combination would be achieved was not reveal
ed, which is typical of Qualcomm; historically, the company has disclosed fe
w details about the processor cores that live inside its chips.
Then in 2006, Qualcomm announced a new chip platform, “Snapdragon,” in whi
ch the Scorpion core would be used alongside several other processors and co
-processors. According to Qualcomm, Snapdragon will serve a range of high-pe
rformance mobile applications, such as high-end smartphones and mobile inter
net devices. Still, there was little information about the Scorpion core its
elf.
In conference presentations this year, however, Qualcomm popped the hood on
the Scorpion core and presented a detailed description of the core’s microa
rchitecture and implementation. The Scorpion core (shown in Figure 1) is sim
ilar to ARM’s Cortex-A8, which also implements the ARMv7 architecture. Like
the Cortex-A8, Scorpion is a superscalar, dual-issue machine, and supports
the powerful, signal-processing-oriented NEON instruction set extensions and
VFPv3 floating-point extensions (referred to collectively on Scorpion as th
e “VeNum” media processing engine). Scorpion will be supported by ARM’s
standard software development tools, and Qualcomm expects to offer off-the-s
helf multimedia codec software that uses VeNum.
Figure 1. Scorpion core block diagram.
Although Scorpion and Cortex-A8 have many similarities, based on the informa
tion released by Qualcomm, the two cores differ in a number of interesting w
ays. For example, while the Scorpion and Cortex-A8 NEON implementations exec
ute the same SIMD-style instructions, Scorpion’s implementation can process
128 bits of data in parallel, compared to 64 bits on Cortex-A8. Half of Scor
pion’s SIMD data path can be shut down to conserve power. Scorpion’s pipel
ine is deeper: It has a 13-stage load/store pipeline and two integer pipelin
es—one of which is 10 stages and can perform simple arithmetic operations (
such as adds and subtracts) while the other is 12 stages and can perform bot
h simple and more complex arithmetic, like MACs. Scorpion also has a 23-stag
e floating-point/SIMD pipeline, and unlike on Cortex-A8, VFPv3 operations ar
e pipelined. Scorpion uses a number of other microarchitectural tweaks that
are intended to either boost speed or reduce power consumption. (Scorpion’s
architects previously designed low-power, high-performance processors for I
BM.) The core supports multiple clock and voltage domains to enable additio
nal power savings.
In addition to developing a custom microarchitecture, Qualcomm also customiz
ed the core’s circuit design and layout in an effort to improve energy effi
ciency.
Overall, Qualcomm has made a huge investment in creating a custom implementa
tion of the ARMv7 architecture. By way of comparison, Texas Instruments cust
omized just the layout for the Cortex-A8 for its OMAP3 chips, and it has bee
n reported that the process took 45 engineers working for a period of years.
If so, Scorpion’s development probably represents an investment on the or
der of tens of millions of dollars. And what’s the payoff?
At first glance, it doesn’t look like much—as noted earlier, Scorpion is e
xpected to run at 1 GHz in a 65 nm process, which is slightly lower than the
1.1 GHz top speed that ARM currently quotes for the Cortex-A8 in 65 nm. Sco
rpion is quoted as providing 2100 DMIPS at 1 GHz; Cortex-A8 is quoted at 200
0 DMIPS at the same speed. However, a notable difference is that the Cortex-
A8 top speed is for a TSMC GP (general-purpose) process, while the Scorpion
speed is for the LP (low-power) process. ARM quotes the speed of Cortex-A8
in an LP process as roughly 650 MHz, and although TI does not publicize the
exact speed of the hand-crafted, low-power Cortex-A8 core used in its OMAP3
chips, BDTI has estimated that it runs at roughly 450 MHz. (BDTI’s benchma
rk results for the Cortex-A8 are available at BDTI’s website, www.BDTI.com.
) Thus, Qualcomm expects Scorpion to run significantly faster than Cortex-A
8 when both are implemented in the low-power processes commonly used for mob
ile applications.
What about power consumption? Qualcomm claims that Scorpion will have power
consumption of roughly 200 mW at 600 MHz (this figure includes leakage curre
nt, though its contribution is typically minimal in low-power processes). I
n comparison, ARM reports on its website that a Cortex-A8 in a 65 nm LP proc
ess consumes .59 mW/MHz (excluding leakage), which translates into about 350
mW at 600 MHz.
BDTI has not independently verified the above clock speeds or power figures,
but if they are accurate, it appears that Qualcomm’s efforts have yielded
significant benefits in terms of both speed and energy efficiency. Clearly,
Qualcomm is betting that its investment will pay off in chip sales, and that
these improvements will give Snapdragon an edge over key competitors like T
I’s OMAP3430 and Freescale’s i.MX31.
高通：
128b SIMD
两条定点流水10/12stages
一条load store流水线13stages
一条23stages浮点流水
流水线VFPv3
1Ghz for TSMC 65LP
200mW of 600Mhz
ARM Cortex A8：
64b SIMD
非流水VFPv3
1Ghz for TSMC 65GP
650Mhz for TSMC 65LP
350mW of 600Mhz
TI用了45个工程师一年时间进行OMAP3系列里面的cortexA8的layout
Qualcomm Reveals Details on Scorpion Core
By BDTI, 11/14/2007
Back in 2005, Qualcomm announced that it had licensed the ARMv7 instruction
set architecture and was working with ARM to create its own high-performance
core based on that architecture. The new core was dubbed “Scorpion,” and
at the time it was announced, Qualcomm didn’t disclose much about it except
that it would run at 1 GHz in a 65 nm process and would be customized to pr
ovide a high level of performance and energy efficiency in its target mobile
applications. Exactly how this combination would be achieved was not reveal
ed, which is typical of Qualcomm; historically, the company has disclosed fe
w details about the processor cores that live inside its chips.
Then in 2006, Qualcomm announced a new chip platform, “Snapdragon,” in whi
ch the Scorpion core would be used alongside several other processors and co
-processors. According to Qualcomm, Snapdragon will serve a range of high-pe
rformance mobile applications, such as high-end smartphones and mobile inter
net devices. Still, there was little information about the Scorpion core its
elf.
In conference presentations this year, however, Qualcomm popped the hood on
the Scorpion core and presented a detailed description of the core’s microa
rchitecture and implementation. The Scorpion core (shown in Figure 1) is sim
ilar to ARM’s Cortex-A8, which also implements the ARMv7 architecture. Like
the Cortex-A8, Scorpion is a superscalar, dual-issue machine, and supports
the powerful, signal-processing-oriented NEON instruction set extensions and
VFPv3 floating-point extensions (referred to collectively on Scorpion as th
e “VeNum” media processing engine). Scorpion will be supported by ARM’s
standard software development tools, and Qualcomm expects to offer off-the-s
helf multimedia codec software that uses VeNum.
Figure 1. Scorpion core block diagram.
Although Scorpion and Cortex-A8 have many similarities, based on the informa
tion released by Qualcomm, the two cores differ in a number of interesting w
ays. For example, while the Scorpion and Cortex-A8 NEON implementations exec
ute the same SIMD-style instructions, Scorpion’s implementation can process
128 bits of data in parallel, compared to 64 bits on Cortex-A8. Half of Scor
pion’s SIMD data path can be shut down to conserve power. Scorpion’s pipel
ine is deeper: It has a 13-stage load/store pipeline and two integer pipelin
es—one of which is 10 stages and can perform simple arithmetic operations (
such as adds and subtracts) while the other is 12 stages and can perform bot
h simple and more complex arithmetic, like MACs. Scorpion also has a 23-stag
e floating-point/SIMD pipeline, and unlike on Cortex-A8, VFPv3 operations ar
e pipelined. Scorpion uses a number of other microarchitectural tweaks that
are intended to either boost speed or reduce power consumption. (Scorpion’s
architects previously designed low-power, high-performance processors for I
BM.) The core supports multiple clock and voltage domains to enable additio
nal power savings.
In addition to developing a custom microarchitecture, Qualcomm also customiz
ed the core’s circuit design and layout in an effort to improve energy effi
ciency.
Overall, Qualcomm has made a huge investment in creating a custom implementa
tion of the ARMv7 architecture. By way of comparison, Texas Instruments cust
omized just the layout for the Cortex-A8 for its OMAP3 chips, and it has bee
n reported that the process took 45 engineers working for a period of years.
If so, Scorpion’s development probably represents an investment on the or
der of tens of millions of dollars. And what’s the payoff?
At first glance, it doesn’t look like much—as noted earlier, Scorpion is e
xpected to run at 1 GHz in a 65 nm process, which is slightly lower than the
1.1 GHz top speed that ARM currently quotes for the Cortex-A8 in 65 nm. Sco
rpion is quoted as providing 2100 DMIPS at 1 GHz; Cortex-A8 is quoted at 200
0 DMIPS at the same speed. However, a notable difference is that the Cortex-
A8 top speed is for a TSMC GP (general-purpose) process, while the Scorpion
speed is for the LP (low-power) process. ARM quotes the speed of Cortex-A8
in an LP process as roughly 650 MHz, and although TI does not publicize the
exact speed of the hand-crafted, low-power Cortex-A8 core used in its OMAP3
chips, BDTI has estimated that it runs at roughly 450 MHz. (BDTI’s benchma
rk results for the Cortex-A8 are available at BDTI’s website, www.BDTI.com.
) Thus, Qualcomm expects Scorpion to run significantly faster than Cortex-A
8 when both are implemented in the low-power processes commonly used for mob
ile applications.
What about power consumption? Qualcomm claims that Scorpion will have power
consumption of roughly 200 mW at 600 MHz (this figure includes leakage curre
nt, though its contribution is typically minimal in low-power processes). I
n comparison, ARM reports on its website that a Cortex-A8 in a 65 nm LP proc
ess consumes .59 mW/MHz (excluding leakage), which translates into about 350
mW at 600 MHz.
BDTI has not independently verified the above clock speeds or power figures,
but if they are accurate, it appears that Qualcomm’s efforts have yielded
significant benefits in terms of both speed and energy efficiency. Clearly,
Qualcomm is betting that its investment will pay off in chip sales, and that
these improvements will give Snapdragon an edge over key competitors like T
I’s OMAP3430 and Freescale’s i.MX31.