MIPS也是蛮拼的，但真有机会逆袭ARM吗？

Why MIPS? Imagination Makes Its Case

Junko Yoshida

Does the industry know everything it needs to know about MIPS? Most industry analysts think they do.

And they’re probably right. MIPS processor cores’ architecture and its power-efficient performance are an integral part of the well told MIPS legacy.

Industry observers’ enthusiasm for MIPS tends to be muted, if not non-existent, largely because the world has already decided that MIPS has lost the mobile battle against ARM.

MIPS’s market position might still prove to be different in the nascent wearable device market, or in more established networking and home entertainment segments. But at a time when there is not a single MIPS-based application processor designed for smartphones on the global market, MIPS is a non-player in the mobile world. Realistically, it isn’t even an “underdog.”

For Imagination Technologies, the new owner of MIPS, to change the narrative is hard, and to reverse the momentum is even harder.

But that’s not to say that the company shouldn’t be trying.

Imagination recently put together two sets of comprehensive presentations -- one illustrating how Imagination is enabling “innovation in SoCs across many markets,” and another on “innovation in mobile SoCs.”

Most industry analysts I contacted find no news in just another PowerPoint presentation. Linley Gwennap, principle analyst of The Linley Group, was blunt: “What Imagination really needs is to announce some new MIPS customers -- to show some market momentum.”

Well put.

It’s hard to argue with Gwennap, but the Imagination presentations offered me a broader view of the company’s strategy and a few new nuggets about MIPS CPUs.

At the risk of repeating what you might already know about MIPS/Imagination, here are a few facts about where MIPS stands, and some clues to the big picture Imagination hopes to paint for its new customers, if there are any. We sum them up in the following eight pages.

IP and IP blocks

Both ARM and Imagination offer CPUs and GPUs. What difference does Imagination bring to the table? The distinction lies in the breadth of IP blocks the two companies offer, according to Imagination.

Beyond CPU and GPU cores, Imagination now offers a variety of IPs ranging from hardwired video encoder/decoder blocks (PowerVR video processing unit) and an Ensigma radio processing unit for WiFi to Bluetooth, digital, and analog TV/radio.

Imagination's other IPs include image signal processing (PowerVR ISP), a security block (Ensigma network processing unit), and an audio engine (MIPS MCU).

Currently, ARM offers no IPs for radio processing equivalent to Imagination's Ensigma.

Imagination believes it has an edge over its competitor by offering more IP blocks that, in theory, make it easy for chip vendors to shop for what they need and develop their own SoCs.

The point here is that Imagination isn't in the business of just pushing MIPS CPUs and PowerVR GPUs. Mobile isn't the only market Imagination is after, either. Other target markets include wearable and IoT devices, home entertainment, routers, home/enterprise networking, and automotive.

As Jim McGregor, founder and principal analyst at Tirias Research, told us, "Imagination is and wants to use any or all of its IP to win opportunities in these markets."

Against that backdrop, Imagination takes a long view in promoting MIPS CPUs.

The company also encourages a variety of business models, under which some chip vendors might just license individual IP blocks or opt for subsystem IPs. Vendors can take Imagination's platform offering. Some companies even ask Imagination to develop a complete SoC, in which case Imagination, through another outfit, does the job and gives a net list to its customer.

Next page: MIPS performance (CoreMark/MHz)

MIPS performance (CoreMark/MHz)

From a high-end processor like MIPS P5600 to a mid-range CPU such as MIPS InterAptive CPU and a microcontroller CPU like MIPS M51, Imagination boasts that each MIPS core consistently scores higher CoreMark/MHz across the board, when each CPU is compared to its competitors' equivalent offerings. (These are "apple-to-apple" comparisons, according to Imagination, as it compares each at the same process node, the same L1/L2 cache, etc.)

Click here for larger image

(Source: Imagination Technologies)

As you can see in the bar graph above, the difference in performance is about 10 percent at the same frequency between MIPS's P5600 vs. ARM's apps processor CPU. Where MIPS sets itself apart further is in its performance in power consumption (CoreMark/mW) and area (CoreMark/mm2), according to Imagination.

Next page: MIPS power (CoreMark/mW) and area (CoreMark/mm2)

MIPS power (CoreMark/mW) and area (CoreMark/mm2)

Take the example of MIPS P5600 CPU intended for high-end apps processors in the mobile market. MIPS P5600 CPU performance at CoreMark/mW is at least 50 percent lower than that of competitors', thus allowing Imagination to make the case for MIPS lower power performance advantage. The bottom line: "You don't need to overclock CPU -- thus running it hot -- in order to achieve the same performance at the same frequency," said an Imagination spokesman.

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(Source: Imagination Technologies)

When it comes to the CPU area (see below), a cluster of MIPS P5600 CPUs uses 30 percent less area than that of a cluster of a competitor's CPUs, according to Imagination.

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(Source: Imagination Technologies)

Next page: Thermal throttling

Thermal throttling

When a chip (CPU, GPU, or SoC) reaches a temperature limit, it will reduce frequency to cut heat and temperature. Using a technique known as "CPU throttling" in computer architecture, a mobile device automatically adjusts the frequency of a microprocessor either to conserve power or to reduce the amount of heat generated by the chip.

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(Source: Imagination Technologies)

The recently released GFXBench 3.0 (shown above) illustrates that PowerVR GPUs (both PowerVR SGX GPU and PowerVR Rogue GPU) continuously maintain high-level performance even in the 30th run -- which is equivalent to a smartphone user running graphics-intensive applications, such as game or navigation, on a mobile device for 15 to 20 minutes.

In contrast, the competitor's GPUs get too hot after a while, forcing performance to drop 20 to 30 percent. After all the pixels are drawn and everything is rendered, maintaining continuous performance is important. That's when power-efficient architecture matters, says Imagination.

Next page: Mapping out Imagination's IPs for mobile

Mapping out Imagination's IPs for mobile

Bluntly put, many players in the electronics industry today are not sanguine about the survival chances for MIPS processors in a global mobile market where, in the last decade, ARM has built its formidable ecosystem.

In short, "There's not much [Imagination] can do to move the CPU needle in their direction for mobile," says Mike Demler, senior analyst at The Linley Group.

But that doesn't mean there is no opportunity in the mobile segment for Imagination. In the following chart, Imagination maps out how a variety of IPs offered by Imagination would fit into a range of mobile devices including ultra-affordable devices and high-end smartphones.

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Mapping out Imagination's IPs in smartphones and tablets

(Source: Imagination Technologies)

Although no single MIPS-based apps processors exist today for mobile devices, Imagination is hopeful for its full IP portfolio to attract new licensees.

Next page: MIPS for automotive?

MIPS for automotive?

I'm the first to admit that I've known little about where MIPS is going on the automotive market. Nonetheless, Imagination is bullish about potential opportunities for Imagination's IP blocks in automotive. Shown below is how its IP offerings could potentially fit in automotive -- everything from sensors/connectivity to safety critical apps and infotainment and navigation platforms.

Thus far, Renesas and Texas Instruments are the giants using Imagination's PowerVR GPUs for the chips in their in-vehicle infotainment clusters. How that might propagate into other parts of in-vehicle devices remains largely unknown.

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Mapping out Imagination's IPs for automotive

(Source: Imagination Technologies)

Next page: MIPS in wearable devices

MIPS in wearable devices

Even those industry analysts most pessimistic about MIPS's chances in the mobile world are more hopeful for MIPS in the wearable device market.

Why?

Linley Gwennap, principle analyst of The Linley Group, tells us, "The combination of IP that Imagination offers, particularly with the Bluetooth block that ARM lacks, is well suited to wearable devices... For these wearables as well as for many digital-home (e.g., set-top box, Blu-ray) devices, apps are not important because the device generally ships with all of its software."

Imagination has been proactive in building an enabling infrastructure for IoT device vendors. Earlier this year, the company rolled out an application-independent platform called FlowCloud, designed to enable fast construction and management of machine-to-machine and man-to-machine connected services.

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(Source: Imagination Technologies)

Those who have never built IoT or cloud-connected devices should be able to get help from FlowCloud technology, according to Imagination. FlowCloud services include registration, authentication, association, security notification, updates, and report control.

As for developing IoT devices, Imagination's partners have created several reference platforms with full support for FlowCloud. For one, the chipKIT Wi-Fire development platform from Digilent uses a PIC32 microcontroller (MCU) with a MIPS microAptiv CPU and boasts on-board WiFi.

(Source: Imagination Technologies)

Next page: Proverbial ecosystem

Proverbial ecosystem

Doubters about the market momentum behind MIPS tend to point out the lack of "ecosystem" around MIPS.

As Jim McGregor, founder and principal analyst at Tirias Research, notes, "The most difficult challenge MIPS faces is overcoming the momentum and build-out of the ecosystem around other architectures, particularly ARM."

Imagination, when both MIPS CPUs and PowerVR GPUs are combined, does offer a pretty big ecosystem that includes tools, middleware, software, and apps. But when it comes to the ecosystem for CPUs in mobile, the story is different.

Says McGregor: "How do you overcome an ecosystem that is now driving the direction of technology all because of its success in the most important platforms -- mobile devices? Everyone from server vendors to embedded applications is now looking to leverage the success and breadth of the mobile ecosystem, and that is all built around ARM at this point."

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Imagination is in search of IP sockets in SoCs across many markets.

(Source: Imagination Technologies)

Imagination's latest presentations have assured us that the company does have very competitive IP in a number of areas. Imagination also makes it clear that plugging MIPS into a mobile socket isn't the most important thing for Imagination. More important is for Imagination to win as many sockets as possible in a wide variety of product applications -- beyond mobile.

But in the end, as McGregor points out (and many others agree), "What would help Imagination's messaging is some success stories."