The newest processor from VIA, C7-M, is targeted to the mobile market and, according to VIA, competes directly with Pentium M (Centrino platform), as you can see in Figure 1. In this article we’ll explore this new baby from VIA.
In fact, the slide presented in Figure 1 is really interesting: the mobile market can be divided into five categories, and each CPU for this market is targeted for some categories. For example, Turion 64 is targeted to Transportable, Full Size and Thin & Light categories, while Pentium M and C7-M are targeted to Full Size, Thin & Light, Mini-Note and Ultraportable categories.
Figure 1: Mobile market segments.
| Category | Screen Size | Weight | Height |
| Transportable | >= 15” | > 7.5 lbs (3.40 Kg) | >= 1.8” (47.58 mm) |
| Full Size | >= 15” | 6.5-7.5 lbs (2.95-3.40 Kg) | >= 1.3” (33.02 mm) |
| Thin & Light | 14-15” | 4.5-6 lbs (2-2.72 Kg) | 1.1-1.2” (27.94-30.48 mm) |
| Mini-Note | 12” | 3-4.5 lbs (1.36-2 Kg) | > 1.0” (25.4 mm) |
| Ultraportable | 8-10” | < 3 lbs (1.36 Kg) | > 0.85” (21.59 mm) |
The size of C7-M is really impressive. Measuring only 0.83” x 0.83” x 0.073” (21 mm x 21 mm x 1.85 mm) it is really hard to believe that it has all the features claimed by VIA.
Figure 2: VIA C7-M Processor.
Figure 3: VIA C7-M Processor.
[nextpage title=”Main Specifications”]
The C7-M processor main specs include:
- 90 nm process;
- Low power design (average power below 1 W and 0.1 W when idle with a maximum TDP – Thermal Power Design – of 12 W at 1.5 GHz and 20 W at 2 GHz);
- 128 KB L1 memory cache and 128 KB L2 memory cache;
- External clocks of 400 MHz, 533 MHz and 800 MHz (in the future);
- Two internal clocks (called “TwinTurbo” technology by VIA), the second clock, which is smaller, is used for running the CPU in a low-power state in order to save battery life;
- Integrated security co-processor, called “PadLock”;
- NX bit (prevents virus attacks if you use Windows XP SP2);
- MMX, SSE, SSE-2 and SSE-3 support.
Figure 4: Micro-architecture of VIA C7-M processor.
Figure 5: VIA C7-M main features.
Figure 6: VIA C7-M main features (cont’d).
Figure 7: VIA C7-M main features (cont’d).
[nextpage title=”Security Co-Processor (PadLock)”]
VIA C7-M includes a unique feature that is a security co-processor, called PadLock. Mobile computers face a huge security problem, since if your mobile computer is stolen or lost, anyone can gave access to your data. PadLock is basically an encryption engine, a hash engine and also a random number generator (RNG).
The encryption engine supports all AES modes and according to VIA, C7-M is capable of performing encryption at a rate of up to 25 GB/s.
PadLock co-processor also has a hash engine, which is used to check if a data was altered. According to VIA, C7-M is capable of performing hashing at a rate of up to 20 GB/s and it supports SHA-1 and SHA-256 methods.
The security co-processor also has a Montgomery Multiplier engine, accelerating calculations required by RSA encryption algorithms.
And finally, PadLock incorporates two random number generators, with a performance up to 12 MB/s. Random number generators are key to encryption because they generate true random numbers. When the computer doesn’t have this feature (almost all computers don’t have), a random number is generated using the real time clock. So a hacker, knowing more or less the date and time you created a random key, can break it more easily using proper tools.
Figure 8: Main features of C7-M PadLock co-processor.
In Figure 9 you have a security features comparison between VIA C7-M and other mobile processors.
Figure 9: Security features comparison.
[nextpage title=”Power Saving Features”]
The main concern with mobile computers is battery life. What is the use of a mobile platform with a battery that can last only one hour?
Like processors from both Intel and AMD, VIA C7-M also changes its voltage and frequency depending on the computer usage, saving battery life. But what is unique to C7-M is the use of two clock generators (a.k.a. PLL, Phase Lock Loop). On other CPUs there is just one clock generator and when the CPU needs to lower the clock, it has to send a command to the clock generator, which takes time. On VIA C7-M is just a matter of switching the clock generator, which is faster. According to VIA, on C7-M this process takes only one clock cycle, while on Pentium M the same feature requires 15,000 clock cycles.
Figure 10: VIA C7-M Power saving features.
Figure 11: Comparison between VIA TwinTurbo and Intel Enhanced SpeedStep technologies.
VIA claims that the battery of a notebook with C7-M lasts over 5 hours of continuous operation.
[nextpage title=”Comparison”]
In Figure 12, you can see a power consumption comparison between C7-M, Pentium M and Celeron M. According to this data, at 1.5 GHz, VIA C7-M dissipates 12 W, while Pentium M dissipates 21 W and Celeron M dissipates 24.5 W. At 1.8 GHz, C7-M dissipates 15 W while Pentium M dissipates 27 W.
Figure 12: Power consumption comparison between C7-M and Pentium M and Celeron M.
As for performance, VIA published the data shown in Figure 13, making a “performance/watt” comparison. Really interesting, but… beware! This data talks about a ratio, not about absolute values…
Figure 14: Performance/watt comparison.
A final comparison table can be seen in Figure 15.
Figure 15: Comparison table between C7-M, Pentium M and Celeron M.
[nextpage title=”Conclusions”]
This new VIA CPU seems really amazing, but we have to wait and see for its performance. Honestly, VIA doesn’t have a good track on this field. Just remember VIA C3 processor, that running at 750 MHz was slower than a Celeron running at 566 MHz. It is true that C3 power consumption was far lower than Celeron’s, but for desktop market, who cares?
On the other hand, for the mobile market power consumption is the ultimate goal, and the Holy Graal is to have a notebook with good performance with a battery lasting at least eight hours. Will VIA C7-M help industry go in this direction?
Data published by VIA seems interesting, but the only performance comparison provided was the tricky performance/watt ratio, which seems great but since VIA said that C7-M has a power consumption 40% lower than Pentium M, even with a 39% performance difference in favor to Pentium M, VIA C7-M would show a better performance/watt ratio than Pentium M’s.
On the other hand, the embedded security co-processor is a great idea, and we wonder why other companies haven’t think of this before. Another great idea from VIA was to use two clock generators, which provides a faster way to switch between two clock speeds in order to save battery life.
- For more information: https://www.via.com.tw
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