Although there is the whole bunch of all sorts of mainboards today, there is a comparatively poor choice of dual-processor mainboards available on the market. Regardless of the fact that systems like that are a bit more expensive than common configurations, they do not lose their attractiveness for a whole army of users. One of the reasons is that SMP systems are notably better at processing data in one or several applications simultaneously than those single-processor ones. So, in case the system is dealing mostly with tasks of this kind, dual-processor systems seem really worth trying to use, even though they are more expensive.

For a relatively long while the cost of dual-CPU mainboards was a sheer predicament for small servers and graphics stations built with two processors. The situation has recently changed, however. As soon as ABIT BP6, a new mainboard built on a "non-server" i440BX chipset and boasting a really acceptable price, appeared on the market, dual-processor systems started their way to mass production. Some time later VIA followed in the footsteps of ABIT and provided its most popular chipset, Apollo Pro 133A, with dual-processor support. As a result, you can now buy a dual-Socket370 mainboard for about $120-$150. However, this was just the beginning. Dual-processor mainboards based on VIA Apollo Pro133A proved popular enough, so VIA didn't want to lose precious time and without any hesitation introduced dual-processor support into its on-going chipset for Socket370 platform, Apollo Pro266. Dual-processor mainboards built on this new core logic became especially attractive for manufacturers, since VIA Apollo Pro266 was the first chipset for Pentium III CPUs, supporting the new highly promising DDR SDRAM.

The first mainboard manufacturer, which took the risk of making a dual-processor product based on VIA Apollo Pro266 became Iwill, that is well known for its High-End solutions. Like some other leading hardware sites, we were lucky to receive a brand new mainboard from Iwill: DVD266-R, supporting two Socket370 CPUs and DDR SDRAM. Before we pass over to the results of our tests run on this super-mainboard, let us say a few words on the advantages provided by DDR SDRAM in dual-processor systems built on Intel Pentium III CPUs.

VIA Apollo Pro266: Two Pentium III CPUs and DDR SDRAM

VIA Apollo Pro266 core logic differs tangibly from its predecessor, Apollo Pro133A. Apart from DDR SDRAM support, it is the first one to feature a new V-Link bus, which is used to connect the North and the South Bridges. Its bandwidth is two times higher than that of the commonly used PCI bus. We have already discussed VIA Apollo Pro266 in one of our recent reviews, so this time we shall confine ourselves to a mere list of its basic characteristics:

• Supports one or two Intel Pentium III processors, Intel Celeron and VIA Cyrix III;
• 66/100/133MHz FSB;
• AGP 4x interface;
• Up to 4GB PC2100/PC1600 DDR SDRAM as well as PC133/PC100 SDRAM;
• V-Link bus with 266MB/sec bandwidth, connecting the South and the North Bridges;
• ACR support;
• Integrated six-channel AC-97 audio;
• Integrated MC-97 modem;
• Integrated 10/100 BaseT Ethernet controller or Home PNA;
• ATA-100 protocol support;
• Up to six USB ports.

As you can see, VIA Apollo Pro266 originally features dual-processor support. Indeed, the dual-processor Iwill DVD266-R, which is based on this chipset, is equipped with the same VT8633 North Bridge as regular mainboards.

Speaking about the specs, it turns out clear at first glance, that VIA Apollo Pro266 fits much better for small servers and workstations than the chipsets from Intel and ServerWorks. But its main advantage is the support of DDR SDRAM, which boasts great bus bandwidth and reasonable price. To corroborate all these statements we enclose a chart, delivering some information about those chipsets that are currently used in dual-processor Socket370 mainboards:

As it comes from the chart, there is just one thing VIA Apollo Pro266 lacks to become a fully fledged server chipset - PCI64 support. Nevertheless, we have some good news for VIA admirers: in the nearest future the company plans to introduce PCI64 support to its chipsets by means of one more VPX chip. The latter will be connected to the North Bridge via V-Link. The first product from this series will be VIA Apollo Pro266T, arriving this spring.

Now that we have mentioned the highs, it's time to focus on some disadvantages of VIA Apollo Pro266. The most important thing about this core logic is its usefulness. In our VIA Apollo Pro266 Review we showed that it is no use adding DDR SDRAM support to Pentium III platforms, because the bandwidth of AGTL+, the processor bus used in Pentium III at 133MHz, makes only 1.06GB per second, which is equal to that of PC133 SDRAM. An increase in the memory bus bandwidth doesn't affect the processor bus in any way. Eventually, in Pentium III systems with DDR SDRAM the CPU bus becomes a bottleneck, as it confines the data transfer rate between the CPU and the memory to the notorious 1.06GB/sec. This way, it makes no sense increasing the memory bus bandwidth without doing the same thing with the processor bus. That was exactly what we observed in the previous tests with VIA Apollo Pro266 based platforms: the system with DDR SDRAM basically proved no faster than the one built on the standard i440BX with the FSB overclocked to 133MHz.

It seems at first that in case of dual-processor configurations using DDR SDRAM may lead to more notable results, as long as there are two CPUs to work with the memory and thus to make full use of the high bandwidth of DDR SDRAM. Unfortunately, this impression is a false one, and again it is AGTL+ processor bus, which is to blame. The matter is that dual-processor support is implemented in systems with Intel CPUs in such a way that the processor bus bandwidth is not increased, but just shared among the CPUs. This is totally different from the AMD processor based systems with EV6 bus, where each CPU of the system has its own processor-to-chipset connection.

AGTL+ Processor Bus		EV6 Processor Bus

In case of single-processor configurations the performance difference between Socket 370 systems with SDR and DDR memory reached its maximum at the point of 7%, while by Athlon systems, where the processor bus bandwidth equals to that of DDR SDRAM, using DDR provided a gain of 20%. Like in regular systems, the processor bus in dual-processor DDR platforms built on Intel CPUs is again a serious bottleneck and doesn't let DDR SDRAM reveal all its advantages. That's why we have to state that there is no substantial performance gain to be awaited from using DDR SDRAM in dual-processor Pentium III systems.

So far DDR memory in both: single- and dual-processor systems based on Intel CPUs, might be reasonable only if its price didn't differ that greatly from that on PC133 SDRAM. Unless DDR SDRAM is cheaper than it is now (and now it is much more pricy than the regular PC133), it makes hardly any sense to switch over to mass use of DDR. Unfortunately, VIA Apollo Pro266 can't be compared to i840 from this point of view, because in case of i840 adding the second Rambus channel did tell positively on the performance. The thing is that unlike i820 with just one Rambus channel, i840 enjoys greater memory bus bandwidth alongside with lower latency, achieved by channels interleaving. Technologically DDR SDRAM doesn't allow lowering the latency, but only increases the memory bus bandwidth and that's it.

Closer Look

Despite all the above mentioned facts, Iwill DVD266-R is the first dual-processor mainboard with DDR SDRAM support, and it appears an extremely interesting product, which we simply couldn't leave out. Please meet our today's newcomer: the recently announced Iwill DVD266-R:

We would like to point out that Iwill is not the only manufacturer that plans to make dual-processor mainboards built on VIA Apollo Pro266. Supermicro, for example, is also known to have a similar product on its roadmap. However, Iwill again turned out smart enough to be the first to introduce its dual-processor mainboard with DDR SDRAM, just like in the previous case with Socket370 DDR board, as you remember.

Looking at Iwill DVD266-R, one can notice that its outlook resembles dual-processor boards based on VIA Apollo Pro133A core logic. Like in most products of the kind, both processor sockets are turned at 90 degrees to each other. We shall pinpoint that although such allocation of processor sockets is the most common nowadays, it cannot be viewed as the most optimal one. At least it's quite hard to cool both the CPUs well enough: air flows from the coolers will cross each other and will not provide efficient air cooling inside the case. For this reason DVD266-R may need extra coolers inside the PC case to ensure its stable and reliable operation.

Moreover, the capacitors that are placed around the CPU sockets come too close to one of them, so it may cause some troubles when installing coolers larger than Socket370 (for example, the utterly popular Golden Orb).

Speaking about the CPUs, we should mention that Iwill DVD266-R allows using all Socket370 processors for single-CPU configurations, while for dual-CPU ones suit only Pentium III processors supporting SMP. As for the list of the series (S-Spec) of those CPUs, which can work in pairs, you can consult our Gigabyte GA-6VXDC7 Review. When Iwill DVD266-R works in a single-processor mode, the second CPU socket requires no traditional terminator, since the board is already equipped with an automatic terminator of AGTL+ processor bus.

As soon as Iwill DVD266-R is targeted at the server and workstation sector, it looks sensible that the board features four DIMM slots. Moreover, all four of them are 184-pin slots and are devised for PC2100/PC1600 DDR SDRAM. This way, as DDR SDRAM modules with the capacity of up to 1GB are to arrive in the nearest future, Iwill DVD266-R can work with a memory subsystem of 4GB maximum.

Unlike DDR chipsets by other manufacturers, VIA Apollo Pro266 chipset lets treat the memory asynchronously with the FSB. For the users it means that when CPUs with a 133MHz FSB are used, Iwill DVD266-R can work not only with PC2100 DDR SDRAM, but also with 100MHz PC1600 DDR SDRAM. Correspondingly, with processors supporting 100MHz bus, the memory bus on DVD266-R can be adjusted to work at 133MHz, i.e. to support PC2100 DDR SDRAM. Settings of the memory subsystem can be changed via BIOS Setup. For this purpose there is a special page in the Setup, where one can change the memory bus frequency and adjust the timings:

As for expansion slots, Iwill DVD266-R features 1 universal AGP slot, which supports AGP 2x and 4x graphics cards, 5 PCI slots and 1 ACR slot (Advanced Communication Riser), which is worth discussing in detail. This slot was first supported by the South Bridge of VIA Apollo Pro266 chipset. It is situated in the left corner of the board and resembles a standard PCI connector turned by 180 degrees. In fact, AMD introduced it as an alternative to CNR slot and provided it with a good deal of advantages. First, unlike CNR, ACR is backward compatible with AMR, i.e. it supports old AMR cards without any problems. Then, in comparison to CNR, which supports modems, HPNA, Ethernet and audio cards, ACR also enables us implement DSL and wireless network.

We would like to stress that although Iwill targets DVD266-R at workstations among other applications, this mainboard is equipped with an ordinary AGP slot, but not an AGP Pro. Consequently, AGP Pro graphics cards with high power consumption (among them some professional graphics cards) cannot be used on DVD266-R.

To make up for the above described shortcoming, Iwill has provided its new mainboard with a couple of additional features. First, DVD266-R has an integrated ATA-100 IDE RAID controller, AMI MG80649, which is actually a remarked CMD 649 controller. This way, this board has four IDE channels supporting ATA-100 protocol. Moreover, the hard disk drives, which are connected to a pair of channels of a supplementary controller, can build the following RAID arrays: 0, 1 or 0+1 level (mirror, stripe, mirror+stripe). This controller is operated via its own BIOS. The disk arrays are created in the same BIOS, here is a screenshot:

By the by, if you do not want to pay any extras for the RAID controller on the board, you may wait for a special modification of this board, DVD266, that will have no RAID controller and hence will cost about $20 less.

Well, the IDE RAID controller on the mainboard meant for servers and workstations looks wise enough, no doubt. But the second peculiarity of DVD266-R, we mean the integrated C-media CMI-8738 PCI sound controller, seems a bit strange. In fact, this five-dollar chip doesn't tell much on the final price of the board, so it may be simply considered a "free" supplement. Of course, this controller provides sounding of significantly higher quality than the commonly installed AC'97 software codecs, besides it hardly loads the CPU when playing the sound. Moreover, since C-media CMI-8738 chip supports output to five-component acoustic systems alongside with 3D sound, most users should surely be satisfied with the features and sound quality of the sound controller on Iwill DVD266-R, naturally, if they make full use of it. If not, then you can disable the integrated onboard sound by switching a special jumper.

Another thing that is important for server mainboards is built-in hardware monitoring. That's why Iwill didn't use the poor monitoring abilities supported by the chipset South Bridge of DVD266-R, and turned to a controller, built into Winbond WB83627HF microchip. As a result, the board supports three thermal sensors. Two of them control the temperatures of both CPUs. These temperatures are measured by thermal diodes, which are built into the processor cores, thus ensuring higher precision. The third sensor, an external one, is intended to control the temperature inside the PC case. It is plugged into a special connector on the board and measures 9 voltages. Apart from that, the board features four fan connectors. The rotation speeds of three of them may be also controlled.

As a final word in the general mainboard description, we considered it useful to bring some details about its layout. The creators of Iwill DVD266-R did their best to make the board as compact as possible, in order to avoid any troubles with installation. They did succeed, actually: this mainboard is only 26cm long, which is good even for a single-processor board. However, the small size has aroused another sort of trouble: some components are located just awfully! We singled out two most displeasing points: a FDD connector, which is placed in the left corner of the board, and the ATX power supply connector that is squeezed into a tiny gap between the AGP slot and the second CPU socket. In particular, the unwisely placed FDD connector makes its cable stretch all over the case and this way hinder the air circulation greatly. As for ATX power supply connector, it is not only hard to reach, but also blocks the retention mechanism of one of the processor coolers and its cable is a real obstacle for the air flow going from the CPUs.

Overclocking

It's still unsettled, whether overclocking is a necessary option for dual-processor mainboards. All the fuss is that small servers and workstations Iwill DVD266-R is intended for, require high stability. But the stumbling stone comes to the following: overclocking makes the work no safer and leads to even greater instability. In spite of this trend, Iwill ventured to satisfy the needs of the vast army of overclockers and to please them with the overclocking abilities of DVD266-R.

So, in BIOS Setup of DVD266-R we can find the company's brand Microstepping Iwill Smart Setting technology. Here is a screenshot:

Iwill Microstepping is a very powerful thing that enables the users to vary the FSB frequency with an increment of 1MHz. As for the range of supported frequencies, it surpasses all the expectations: from 66 to 200MHz! No doubt, even extreme overclockers will stay content with these figures.

As far as other necessary overclocking functions are concerned, Iwill DVD266-R makes it possible to set the processors Vcore via BIOS Setup as well. The only drawback is that it can be done only for both processors at a time. The board offers any value from the interval between 1.6V and 2.05V with an increment of 0.05V. Following the idea, Vcore of Coppermine processors can be made tangibly higher, so one should keep in mind that the CPUs require proper cooling especially in case of extreme overclocking (when Vcore grows by over 0.2V), otherwise the CPUs may get burned.

Another overclocking friendly function, Vio increase, it was not implemented on the current Iwill DVD266-R revision.

For those of you who are not willing to use Microstepping Smart Setting, Iwill offers another solution. Like many other mainboards, equipped with the opportunity to overclock the CPU via BIOS Setup, DVD266-R offers an alternative way of setting the FSB frequency: with the jumpers. Surely, in this case all the flexibility comes to naught, while there are only three major frequencies you can actually set: 60, 100 and 133MHz. Speaking of jumpers, we cannot fail to point out that Iwill took great care of those who will use them: these tiny things are are equipped with handy tails. :-)

Testbed and Methods

The main aim of these tests was to assess the effect provided by DDR SDRAM in dual-processor systems built on Pentium III CPUs. For this purpose we compared the performance of a system built on Iwill DVD266-R mainboard with that of a similar system built on VIA Apollo Pro133A dual processor board with PC133 SDRAM.

As a testing sample we chose a newly launched dual-processor mainboard by ESC, D6VAA. This new dual-processor mainboard uses VIA 694X and 686B chips as a chipset, it has three slots for PC133 SDRAM and supports ATA-100 RAID. We fixed our choice at ESC D6VAA, because it was the one to reveal the best performance among dual-processor mainboards built on VIA Apollo Pro133A chipset.

At the same time we decided to compare the performance of two dual-processor systems based on Pentium III with that of a system with Pentium 4. We made our mind to do that, since the configuration with Iwill DVD266-R and PC2100 DDR SDRAM (dual Pentium III) should be close to that of a Pentium 4 system. If we take a dual-processor system with PC133 SDRAM and a board based on VIA Apollo Pro133A, then the cost would be much cheaper than that of a Pentium 4 system.

Then we tested both dual-processor platforms in a single-processor mode. At last, we got three systems to test:

We tested in MS Windows 2000 SP1. Keep in mind that it makes sense working with dual-processor configurations only in operating systems supporting SMP configurations. Unfortunately, neither Windows 98, nor Windows ME do.

Performance

As we have already mentioned in Gigabyte GA-6VXDC7 Review, using dual-processor systems makes sense either only in applications that carry out multi-threaded calculations, or in operating systems with SMP configurations support, when several tasks are fulfilled simultaneously. For this reason it's senseless to test dual-processor systems in some separate applications, which do not support dual processor functioning, like, for example, in most 3D games. In this case the results will just repeat those obtained on single-processor systems. These are the facts we took into account when choosing our tests for this investigation. However, before we proceed to the results, that were shown in real applications, let us take a look at a popular synthetic benchmark SiSoft Sandra 2001. That is what the system built on Iwill DVD266-R mainboard shows:

The algorithm used by SiSoft Sandra 2001 to measure the performance of the CPUs depends neither on the chipset, nor on the memory type. At the same time it enables us to create two calculation threads and to make sure that in theory an ideal dual-processor system may work two times faster than a single-processor one.

The same comment is valid for Multimedia Benchmark, which uses SSE instructions set to measure the performance.

The results of the memory test are of greater interest to us. According to this benchmark, Iwill DVD266-R with PC2100 DDR SDRAM works faster with the memory than the system built on i820 with RDRAM. Although it falls behind the platform built on i840, where the memory subsystem uses two Rambus channels. Now let's look at the results of this benchmark for all the platforms tested:

The chart brings no surprise. Pentium 4 with a double-channel Rambus memory bus and a 400MHz CPU bus is far ahead of all the Pentium III systems. DDR SDRAM in this case provides circa 15% of performance gain in dual processor system. It's interesting that the difference of the memory subsystems performance is smaller in case of single-processor systems than in case of dual-processor ones. It means that dual-processor systems use the memory bus more reasonably.

In the operations that are carried out by FPU, the divergence in the performance of a system with DDR SDRAM and of that with the regular SDRAM is not that big. That is caused by the fact, that it is the CPU bus that slows down Pentium III systems, but not the memory bus. The leader is again the platform built on Pentium 4.

Enough for synthetic tests, it's high time we passed over to benchmarks, based on real applications.

This test models the work of typical business applications and works with the following programs: Norton Antivirus 2000, WinZip 7.0, Microsoft FrontPage 2000, Lotus Notes R5, Microsoft Access 2000, Microsoft Excel 2000, Microsoft PowerPoint 2000, Microsoft Project 98, Microsoft Word 2000 and Netscape Communicator 4.73. Neither of these programs works better in dual-processor systems when run separately from all other apps. However, since Business WinStone 2001 models real conditions when these applications are working, it means that it launches some of them simultaneously, switching over from one application to another, dual-processor systems do provide some performance gain. There is a 2% performance increase provided by DDR SDRAM. This allows Iwill DVD266-R even with one Pentium III 1GHz CPU overtake the system based on Pentium 4 1.5GHz in performance.

Content Creation Winstone 2001 is arranged following the same principle as the previous test, but it uses more complicated applications, meant for content creation: Adobe Photoshop 5.5, Adobe Premiere 5.1, Macromedia Director 8.0, Macromedia Dreamweaver 3.0, Netscape Navigator 4.73 and Sonic Foundry Sound Forge 4.5. As these applications are more sensible to the memory bandwidth, and some of them create a number of parallel calculation threads, the results in this benchmark are more dispersed. Namely Iwill DVD266-R with DDR SDRAM proves 4% better than a similar dual-processor system built on VIA Apollo Pro133A with PC133 memory. We think it's worth emphasizing that in spite of the high memory and CPU buses bandwidth, Pentium 4 system is slower than Iwill DVD266-R with two CPUs in this test.

Then, for a better performance analysis in separately treated applications, we took BAPCo SYSmark 2000. Unlike Winstone 2001, this test loads and fulfills a succession of some particular operations in different applications measuring how fast everything is done. Again the dual-processor Iwill DVD266-R platform turns out faster than those built on Pentium 4 1.5GHz.

Moreover, this test allows looking at the performance shown in each separate application and hence estimating how well multi-threaded calculations are organized in this or that application. Besides, the advantageous influence of the DDR memory is also considered.

We also included 3D Studio MAX R3 in our investigation. It is a sort of standard for multi-threaded calculations. To assess the performance we checked how long it takes the system to render a scene from Anisotropic Wheel at 800x600. The smaller the time, the better the result.

Indisputable leaders in 3D Studio MAX are dual-processor systems. While the result of Pentium 4 1.5GHz is only 6% better than that of a system with a single Pentium III 1GHz, dual-processor systems built on Pentium III prove nearly twice as fast as their single-processor rivals. As for DDR SDRAM, 3D Studio MAX is not sensitive to the memory bus bandwidth. Its performance mostly depends on the CPU computing capacity. That is why we do not see any effect made by the faster memory used here.

After that we could not resist to test the performance of Iwill DVD266-R in Quake3 game, which engine can theoretically involve both processors (SMP support is switched on by the terminal command r_smp 1).

Judging by our previous reviews, Quake3 is one of the most illustrative applications as far as the memory bus bandwidth increase goes. Thus, when we switch over to DDR SDRAM, the performance of Athlon systems flies up and appears about 20% higher. Single-processor Pentium III systems demonstrate just feeble 2% increase. Dual-processor configurations make this value equal to 6%. But still the gain is not that impressive at all: in Pentium III systems the performance of DDR SDRAM is strictly limited by AGTL+ processor bus. So, no wonder that Pentium 4 being very fast in Quake3, remains unbeaten by Pentium III dual-processor systems.

As the resolution grows, the results become confusing. Adding a second CPU to the system leads to a decrease in performance! The phenomenon is hard to explain, but this event shows very well: multi-threaded programming is not an easy task at all and unqualified or inexperienced software developers can not only nullify the effect of a second CPU, but even make the performance fall.

It is worth mentioning, however, that the basic advantage of dual-processor systems in comparison to the single-processor ones doesn't lie with their high performance, though it is certainly important, too. The main thing is that multi-task operation systems supporting SMP configurations are able to distribute between the CPUs all simultaneously working applications (which the operation system considers just calculation threads). So, a dual-processor system allows running two applications in parallel, while single-processor systems are unable to do that. For instance, nothing will prevent you from playing your favorite game, while the other CPU is used for MPEG-encoding. As you see, carrying out several tasks at a time is much easier for dual-processor systems.

To illustrate our statements, we ran a simple test. We measured the performance of the systems in Quake3 (at the resolution of 640x480x16, SMP support off) with a number of WinRAR 2.7 copies (from 1 to 4) were compressing ~500MB directories. The results talk for themselves.

When a third copy of WinRAR was launched, the performance of all single-processor systems, including one built on Pentium 4, which boasted unprecedented results in Quake3, took a drastic plunge. Dual-processors systems, in their turn, kept on demonstrating acceptable gaming performance even with the four WinRAR copies running.

In conclusion we resorted to SPECviewperf benchmark. This test measures the performance of the system in professional OpenGL applications. Still it lacks the support of a multi-processor mode, so do not forget that the figures in the chart cannot be taken to illustrate the performance of SMP systems. We included this benchmark in our review because we have never discussed the results obtained by the systems with DDR and Pentium 4 systems before.

The chart demonstrates that in professional OpenGL applications VIA Apollo Pro266 core logic (the one Iwill DVD266-R is built on) proves better than its predecessor. There is nothing to wonder at. The memory bus of VIA Apollo Pro266 has greater bandwidth, as well as the bus that connects the chipset bridges.

Conclusion

Let's sum it all up. According to the tests, using DDR SDRAM in dual-processor systems built on Pentium III, as well as in case of single-processor configurations, provides an insignificant performance gain of 5-10% only. Unfortunately, the CPU bus used in Pentium III doesn't let us get the same performance gain from DDR SDRAM, as in Athlon systems. Nonetheless, Iwill DVD266-R with two CPUs proved to be faster than the platform for Pentium 4 1.5GHz in almost all the tests. So, those who use operation systems supporting SMP configurations, for instance Windows 2000, may find Iwill DVD266-R quite suitable for their needs. Especially since the configurations built on dual-processor mainboards and chipsets by VIA are cheaper than Pentium 4 systems.

Iwill with its DVD266-R has managed once again to surpass its competitors and to take another move in DDR SDRAM promotion: this time in the server sector. Although this mainboard is not deprived of some shortcomings connected with not the most optimal components allocation, its innovative character easily makes up for all the drawbacks. Iwill DVD266-R supports PC2100/PC1600 DDR SDRAM, which means that with this mainboard you can assemble so far the fastest dual-processor servers and workstations for a not exorbitant price at all. Add to this the overclocking opportunities together with AMI ATA-100 RAID controller implemented on DVD266-R and you will surely find this board even more attractive.