In a fortnight or so we will witness a great number of new mainboards streaming over the market. But although Intel will be the last to launch its own DDR SDRAM chipset for Pentium 4 CPUs, it implies by no means that the mainboard manufacturers will pay no attention to the event. Moreover, not so much time has passed since Intel was an indisputable leader in the chipset market, and nearly all the mainboard manufacturers keep using chipsets from Intel. And if we also remember that Intel has the opportunities to provide really Gargantuan chipset supplies, then we will not be mistaken to say that hardly anyone will stay indifferent to the launch of Intel's new chipset. Especially, since this time Intel is going to present one of the most long-awaited products of the season: i845D.

Among a great variety of new mainboards we first of all notice those manufactured by the most famous brand names. That's why the first i845D based mainboard we got our hands on appeared the novelty from ASUS called P4B266.

Closer Look

ASUS P4B266 is based on a new i845D chipset from the Brookdale chipset family and continues the P4B mainboard family from ASUS. These are what its specifications look like:

ASUS P4B266
Supported CPUs	Socket478 Intel Pentium 4 (Willamette/Northwood core)
Chipset	Intel 845D
FSB Frequencies	100-200MHz
Overclocking Friendly Features	Supports CPU Clock Multiplier Setting and Vcore and Vmem Adjustment
Memory	3 184-pin DIMM slots for PC1600/PC2100 DDR SDRAM Supports up to 2GB memory No ECC support
Expansion Slots (AGP/PCI/ISA/CNR)	1/6/0/1
USB Ports	4 USB 1.1 ports and 4 USB 2.0 ports
Integrated Graphics	No
Integrated Sound	6-channel controller from C-media - CMI8738
Additional Features	Integrated USB 2.0 controller from NEC
BIOS	Award Medallion BIOS v6.0
Form-Factor	ATX, 305x240mm

As we know, i845D is just another stepping (B-step) of the common i845. Therefore, these two chipsets don't differ that greatly from one another, as it might seem at first glance. In fact, the only difference is in the memory controller: the controller of i845D supports PC2100/PC1600 DDR SDRAM, while that of i845 supports only PC133 SDRAM. In order to make the shift to the new i845D easy and fast Intel made both chipsets pin-to-pin compatible. Accordingly, when the mainboard makers will work on their i845D based products, they will be able to get away without introducing any new design for these boards: they can take the i845 based mainboard and simply change the memory slots layout. That is why some i845D based mainboards look very similar to their i845 based predecessors. Getting back to ASUS P4B266, we'd like to stress that ASUS engineers decided not to borrow anything from their previous designs: P4B266 is different from both P4B and P4B-E. The matter is that ASUS decided to implement some absolutely new features in its P4B266 mainboard.

To start with, P4B266 is the first mainboard from ASUS with an integrated USB 2.0 controller. Since Intel hasn't yet introduced a new version of its South Bridge, ICH4, which will support USB 2.0 ports, ASUS made up its mind to use an external controller from NEC. We have already come across a controller of the kind on some MSI mainboards, but now it has a different BGA package and is of smaller size. However, the main idea remained the same: ASUS P4B266 supports four USB 2.0 ports. These ports are located on a special bracket for the case rear panel of the PC, which is supplied together with the mainboard. Although the USB 2.0 devices are not so widely spread so far, we believe there is not so much waiting left before most suppliers of portable data storage and other peripheral devices migrate from USB 1.1 with 12Mbit/sec bandwidth to the faster USB 2.0 with 480Mbit/sec bandwidth.

Well, it's no big deal to install a USB 2.0 chip onto the PCB. A far more important task is to make it work well. For instance, Windows 98 and Windows XP have no support for USB 2.0 protocol: it will appear only when the next Service Pack comes out. The Windows 95/98/ME clan requires special USB 2.0 drivers; for the controller from NEC there exists only a beta-version of these drivers. So, it's a real brain-cracker to make this integrated USB 2.0 controller work. Say, with P4B266 ASUS ships even no drivers for it yet. Today this makes the USB 2.0 controller of ASUS P4B266 nothing more than just a marketing trick. Yet it's too troublesome if not completely impossible to make it work. There is still some hope for the better: Microsoft is supposed to implement USB 2.0 support in Windows 2000 and Windows XP in January, and drivers from NEC for the other operating systems are to appear soon at ASUS web-site.

Like any other i845D based mainboard, ASUS P4B266 supports up to 2GB PC2100/PC1600 DDR SDRAM. Although the chipset itself supports only four memory banks, there are three DDR DIMM slots on P4B266. As a result, all the three memory slots may be engaged only if there are uni-bank (single-side) memory modules installed into at least two of the slots. If there are dual-bank (double-side) memory modules used, you'll be able to install no more than two modules into P4B266 memory slots.

As long as Intel allowed both synchronous and asynchronous memory clocking relative to FSB frequency in its i845D chipset, the BIOS of this mainboard offers two variants of the FSB/memory clocking proportion - 1:1 and 3:4. In case of 1:1, the memory works at 200MHz synchronously with the FSB. When the second variant is set, the memory works asynchronously at 266MHz. Then, the BIOS offers a complete range of settings, which enable the users to adjust the memory timings: CAS Latency, RAS to CAS Delay, RAS Precharge Delay and Active Precharge Delay.

According to the specs, ASUS P4B266 supports the whole range of Socket478 Pentium 4 CPUs including the processors built on the 0.18-micron Willamette and 0.13-micron Northwood core. The board identifies the processor type and automatically sets the necessary Vcore: 1.75V for Willamette and 1.5V for Northwood. As far as FSB and CPU multiplier adjustment goes, ASUS offers two ways of doing it. The CPU multiplier can be set either with the help of the block of dip-switches on the board, or via BIOS Setup. Of course, the JumperFree technology in the BIOS offers you a lot wider bunch of overclocking abilities.

ASUS developers have also thought of such a trifle as the opportunity to use it with old PSUs without an extra 12V power supply cable. Thanks to the brand EZ-Plug technology, ASUS P4B266 can feed a power-hungry Pentium 4 CPU not via a special connector, but via a regular accessory connector like those to which power supply cables of HDDs are connected. Please, keep in mind that the PSU should be powerful enough, though: at least 230W.

Another innovation implemented on ASUS P4B266 is a LED signaling that an incompatible graphics card is installed. All the latest chipsets from Intel including i850, i845 and i845D don't support the old 3.3V AGP 2x graphics cards (those like Riva TNT, SiS 305 or ATi Rage 128 Pro). So, in order to indicate that the board doesn't work because of an inappropriate graphics card, ASUS supplied a special LED telling the user if the card won't work with this mainboard. When common 1.5V graphics cards are used, this LED produces no signals at all.

We'd also like to say a few words about the sound controller integrated into ASUS P4B266. This is the most popular among the mainboard makers C-media CMI8738 chip, which is actually a really smart and quality solution. Among its functions there are 3D audio support and six-channel output. Furthermore, this chip supports digital S/PDIF Out implemented on a special bracket the case rear panel.

ASUS also equipped its new product with an extra "voice" controller from Winbond: W83791SD. This small chip serves to implement another brand technology of ASUS: POST Reporter. Some time ago, following into the footsteps of the other mainboard manufacturers, ASUS began to equip its boards with diagnostics systems. For some reason (most probably, because they're easier to deal with), ASUS chose a voice diagnostics system. This way, if any mistakes during POST arise, ASUS P4B266 tells you in human voice about the problems occurring or about the successful ending of the POST test. The board is accompanied with a special utility called Winbond Voice Editor, which allows replacing the messages of POST Reporter. Besides, there is a set of ready voice messages in several languages. It should be highlighted that the sound quality of POST Reporter is much better than that of similar solutions used by other manufacturers. At least, we had no troubles with figuring out what the reporter said.

If you look attentively at the lower left corner of the board, you'll notice all sorts of connectors crammed in one place. We'll just give a list of devices that can be connected to ASUS P4B266: ASUS iPanel; 4 USB 2.0 ports mentioned above; an extra pair of USB 1.1 ports (a corresponding bracket with the ports for the PC case rear panel is shipped together with the board); Smart Card Reader; Secure Digital memory card and Memory Stick Reader, and a couple of simple modules like an InfraRed-port.

With all this abundance of ports, ASUS engineers contrived to locate them so wisely that the PCB design hardly provokes any negative remarks. The ATX power supply connector, as well as the connectors for IDE devices, are located in one of the best places - right in front of the DIMM slots. The FDD connector, which failed to fit near the IDE connectors, is turned parallel to the PCB surface, so that the FDD cable won't be in the way when full-size expansion cards are installed. The only inconvenience we discovered in ASUS P4B266 layout was the fact that the graphics card installed into the AGP slot would block the DIMM slots clips.

ASUS' own hardware monitoring controller used in P4B266 allows measuring the temperature of the CPU and mainboard, controlling the rotation speed of three fans and monitoring four voltages.

In conclusion to our Closer Look story we'd like to say a word about a curious bunch of utilities shipped with ASUS P4B266. Apart from the already described editor-program for voice diagnostics messages, there are MyLogo program, which allows editing a picture shown during system startup, and ASUS Update Utility serving to update the BIOS from Windows via Internet.

Overclocking

ASUS has always catered for the overclockers' needs. ASUS P4B266 is no exception to this pleasant rule: the board boasts pretty rich CPU overclocking opportunities.

At first we would like to stress that we will not consider the overclocking with the set of dip-switches here, because in case of JumperFree technology there appear much more interesting opportunities worth your attention.

Here's the list of overclocking opportunities offered by ASUS P4B266:

• Opportunity to adjust the FSB frequency. BIOS Setup allows to adjust it in the interval between 100MHz and 200MHz with an increment of 1MHz. Using the terms of Quad Pumped Bus this means that the FSB frequency can be increased from the standard 400MHz up to 800MHz.
• Opportunity to change the CPU clock frequency multiplier via BIOS Setup. This function works only if the multiplier is not locked, though the multiplier is locked in all the presently shipping Pentium 4 CPUs. So, this is a merely formal feature.
• BIOS Setup allows adjusting the processor Vcore. For CPUs built on Willamette the Vcore can vary from 1.75V to 1.85V with an increment of 0.025V, for those on Northwood from 1.5V to 1.7V with the same increment. For extreme overclockers ASUS P4B266 offers a special jumper, which allows increasing the top limit for Vcore up to 2.1V for Pentium 4 (Willamette) CPUs and up to 1.75V for Pentium 4 (Northwood) CPUs.
• A special jumper serving to increase the Vmem from the standard 2.5V to the over-nominal 2.6V or even 2.7V.
• Opportunity to change all the memory timings and to clock the memory exactly at the FSB frequency, as well as at 4/3 of the FSB frequency. These settings help overclockers to choose an optimal mode for the memory subsystem from the stability and performance point of view.

However, it's not enough to supply an overclocker with all the possible overclocking-friendly features. For successful CPU overclocking a mainboard should have well-planned design and clever CPU power supply circuit, which are to work well at the frequencies far beyond the nominal values.

Aiming to find out how ASUS P4B266 feels at high FSB frequencies, i.e., to define the top frequency at which the board works stably, we ran the following test. We were lucky to find a Pentium 4 CPU sample with an unlocked clock frequency multiplier. We deliberately brought it down to 10x and thus could neglect the overclockability of the CPU itself. Then we took DDR333 SDRAM module from KingMax clocked at the FSB frequency in order to obtain the top of FSB overclocking abilities. These are the results of our experiments:

Yeah, 172MHz for the FSB frequency on a Pentium 4 based mainboard is a really serious thing. Nevertheless, ASUS P4B266 worked quite stably at this frequency. This high overclocking result gives us good grounds to draw some interesting conclusions. Firstly, we can state with all the certainty that when Intel launches its Pentium 4 CPUs using 533MHz Quad Pumped Bus, they will surely work well on ASUS P4B266. Secondly, the overclocking potential of P4B266 is high enough to bring it the status of the best mainboard for Pentium 4 CPUs overclocking. It is also due to the support of DDR SDRAM, which is better overclockable than RDRAM.

Sadly, our experience will not bring you much practical use so far. All the currently selling Pentium 4 CPUs have a locked clock multiplier, which means that it will be only the limited processor overclocking potential that will arouse all the problems. Nevertheless, even in these conditions Pentium 4 CPUs can be successfully overclocked. All you need to do is just to choose the right CPU. :)

The overclockability of Pentium 4 CPUs generally depends on the core stepping. Nowadays, Pentium 4 processors can be built on cores with three different steppings: B2, C1 and D0. B2-stepping is used in 1.3GHz-1.5GHz CPUs, C1-stepping - in 1.3GHz-1.8GHz, D0-stepping - in 1.4GHz-2.0GHz CPUs. Naturally, CPUs with D0 core stepping sport the highest overclockability.

The tests we ran in our lab show that nearly all the CPUs with D0 core stepping can be overclocked up to at least 2GHz, regardless of their nominal working frequency. For example, Pentium 4 CPUs with the "right" core working at 1.5GHz nominal frequency can be easily overclocked to 2GHz by simply increasing the FSB frequency from 100MHz to 133MHz. Due to the fact that ASUS P4B266 allows clocking the memory synchronously with the FSB, the memory bus can go on working at its standard 133MHz (266MHz DDR) even during this overclocking. Subsequently, the "1.5GHz up to 2.0GHz" overclocking is pretty natural for ASUS P4B266 and can fail only if the CPU refuses to work at 2GHz. To avoid problems like that make sure that you get a Pentium 4 CPU with D0 core stepping. For instance, Pentium 4 CPUs working at the nominal 1.5GHz, which are overclockable to 2GHz by increasing the FSB frequency up to 133MHz have the following S-Spec: SL5TN, SL5SX, SL5UF or SL5TJ. If you are looking for more details you're welcome to consult the chart with core steppings and S-Spec for Pentium 4 CPUs. Below we'll investigate the performance of "Intel Pentium 4 1.5GHz up to 2.0GHz" and try to assess the performance gain provided by 533MHz Quad Pumped Bus only (without memory bus overclocking) compared with the performance of a standard Intel Pentium 4 2.0GHz CPU.

Testbed and Methods

Before we pass over to describing our test methods, we'd like to make clear what we have actually tested. A few days ago in our Intel 845D (i845 B-Step) Chipset Review we took a closer look at the performance of i845D chipset having compared it with the other chipsets for Pentium 4 CPUs. So it makes no sense to run any tests of the kind again. If you're curious about the results, please, click here. We haven't got hold of any other i845D based mainboards except the reviewed ASUS P4B266, so we didn't have the opportunity to compare it with any other similar products.

The only way-out for us (far not the worst one, actually) was to do the following. We decided to test the performance of "Intel Pentium 4 1.5GHz up to 2.0GHz" and compare it with that of Pentium 4 2.0GHz, both of them working in ASUS P4B266. A comparison like that is of interest to us because it will let us see the possible performance gain Pentium 4 CPUs can get with 133MHz FSB, since it's only the bus frequency that differs in the systems built on "Intel Pentium 4 1.5GHz up to 2.0GHz" and the regular Pentium 4 2.0GHz.

After that we'll test ASUS P4B266 working with PC1600 DDR SDRAM. We have two reasons to be interested in these results. First, this test gives us a chance to assess the performance of i845D as Intel originally devised it. Second, since PC1600 DDR SDRAM works with the CPU bus at the same frequency, we will be able to figure out whether it makes sense to have i845D working in the synchronous mode, which ensures lower latency of the memory subsystem than the asynchronous mode, i.e. when we use PC2100 DDR SDRAM.

We will compare the results obtained in different modes on ASUS P4B266 with those shown by other two Intel platforms. The first platform will be based on i850 with RDRAM, the second one - on i845 with PC133 SDRAM. As a mainboard based on i850 we took ABIT TH7II, and ABIT BL7 - as an i845 based product.

So, these are the systems that took part in this test session:

We tested in Windows XP.

Performance

The first thing to look at is the practical bandwidth of the memory subsystems tested with the help of SiSoft Sandra 2001:

The factual bandwidths lineup strictly corresponds to the theoretical values. The only notable fact worth your attention here is the almost identical performance shown by i845D working with 100MHz and 133MHz FSB. As we can see, the synchronous work of the CPU and memory buses at 133MHz FSB doesn't give any boost to Pentium 4 based systems - the data exchange with the memory doesn't go any faster.

Now let us have a look at how the performance depends on the memory bus bandwidth in Pentium 4 systems:

As you may notice, the increase in the memory bus bandwidth over 2.1GB/sec doesn't have any effect as significant as the increase in the memory bus bandwidth up to this value. Though the CPU bus bandwidth in systems with Pentium 4 CPUs makes 3.2GB/sec, it becomes evident that the memory bus bandwidth in Pentium4 systems with PC2100 DDR SDRAM is not the only bottleneck affecting the performance adversely. This gives us a reason to expect that in DDR266 systems we can win something by overclocking the CPU bus up to 133MHz (533MHz in the terms of Quad Pumped Bus).

Tests run in office and content creation applications show that increasing the FSB frequency up to 133MHz gives a modest performance gain of about 1%. At the same time we can see that PC1600 DDR SDRAM combined with i845D gives a no higher result than i845 working with PC133 SDRAM. So, we can only be happy for Intel having added PC2100 DDR SDRAM support to i845D.

In the gaming applications the effect of an overclocked CPU bus becomes more obvious. For instance, in Quake3 the performance of 400MHz and 533MHz Quad Pumped Bus systems differs by approximately 5%. In the end, the i845D based system where the CPU worked at 133MHz FSB managed to overcome even the i850 based platform supporting memory with higher bandwidth.

In Unreal Tournament we observe the same tendency. A faster CPU bus provides greater effect than a faster memory bus.

DroneZ appears to be a game where the memory bus bandwidth matters a lot more than the CPU bus bandwidth.

The results of 3DMark2001 are very similar to what we saw in Quake3 Arena. We'd like to point out that the performance of i845D with PC1600 DDR SDRAM in gaming applications falls somewhat in between the results of i845D with PC2100 DDR SDRAM and i845 with PC133 SDRAM.

Conclusion

Well, ASUS P4B266 mainboard proved to be a good solution built on the new i845D chipset. The CPU overclocking opportunities and informal support of processors with 533MHz Quad Pumped Bus are likely to make it a good basis for a Pentium 4 system.

Highs:

• Stable performance, even during overclocking;
• A wide range of overclocking-friendly functions;
• Excellent performance with 133MHz FSB;
• EZ-Plug technology allowing the use of old power supply units.

• Formal USB 2.0 support;
• High price.