X-bit labs - Print version

This is the first review of Athlon mainboard on new VIA Apollo KX133 chipset. This ATX mainboard is designed for Slot A.Judging by the features it has, it should also become a hit. You may enjoy not onlythe review of the mainboard itself, but also a lot of info on the chipset and its major peculiarities.

More than half a year has passed since AMD's Athlon processors started selling. Thanks to prices lower than thoseof Intel Pentium III CPUs and to a high performance, AMD's processors quickly conquered a niche on the market, aposition the company is unlikely to give up. But as AMD decided to go its own way and created not only a specialSlot A for the new Athlon but also a EV6 system bus different from Intel's GTL+, a new processor naturally needsmainboards based on specially developed chipsets. The first of these chipsets, AMD 750, was announced by AMDtogether with first Athlon models. However, this chipset had a set of features similar to those of i440BX andwas bound to become out of date rather soon. According to AMD's idea, AMD 750 was expected to serve for not verylong and it had to be soon replaced by chipsets from other manufacturers - VIA, SiS and ALI. In fact, that's whatwe were waiting for in the end of the previous year: almost immediately after the release of the first Athlons, VIAannounced its first Athlon chipset - Apollo KX133. Actually, things were not so simple as they might seem. Theproduction of VIA Apollo KX133 chipsets has started only recently, SiS is temporarily out of game due to someproblems with manufacturing plants and the situation with ALI is plainly unclear. <%BANNER[article]%>

Nevertheless Slot A mainboards at last hit the market. They're based not on AMD 750 (aka Irongate), but on thelong-awaited VIA Apollo KX133. The first KX133 based mainboards manufacturer turned out to be ASUS, which, as youremember, wasn't making any haste with the release of AMD 750 based K7M and even kept concealing it from the publicfor a long time. Now times have changed and ASUS doesn't fear the processor-manufacturing giant's wrath anymore.ASUS K7V reviews and descriptions occupy a worthy place in all the new brochures and on ASUS' web-site as well.Let's take a look at this mainboard, too. According to our previous tests of AMD 750 based mainboards, ASUS K7Mwas called one of the best, so now we should expect quite a lot of K7V, too.

VIA Apollo KX133

As it is the first review at iXBT dedicated to a VIA Apollo KX133 chipset based mainboard, let's take a quick look at thechipset ASUS K7V is based on before studying the board itself.

Regarding the main features of VIA Apollo KX133, this chipset is almost identical to VIA Apollo Pro133A. The maindifference between them is, naturally, different system buses supported. VIA Apollo KX133 is designed to supportAlpha EV6 bus, used in AMD Athlon, which transfers the data along both edges of the signal with 100MHz frequency.This means that the actual data transfer rate between the processor and the chipset in VIA Apollo KX133 is 200MHz.Taking into account that the bus is 64bit wide, the throughput is 1.6GB/sec. Just for comparison: the throughput of133MHz GTL+ bus used in Intel Pentium III systems is only 1.06GB/sec.

You should remember that KX133 is intended for Slot A based mainboards. For Socket A mainboards (AMD is planning tostart manufacturing Socket A processors in the nearest future) VIA is going to suggest KZ133 - a modified KX133 chipset.

The main advantage of the new VIA Apollo KX133 chipset compared to the old AMD 750 (Irongate) is the PC133 SDRAM support.AMD 750 with its synchronous architecture couldn't provide functioning of the system bus and memory bus at differentfrequencies. In KX133 which is based on asynchronous principles of VIA Apollo Pro133A this problem is solved. So,while the processor bus uses 100MHz carrier frequency, the memory bus can be clocked to 133MHz. This means that thepeak memory throughput of KX133 systems can reach a 1.06GB/sec level compared to 800MB/sec of AMD 750 systems.Taking into consideration that nowadays memory bus throughput is the main bottleneck of Athlon based systems, itsincrease is a primary task for chipset designers. Yet a 33% memory frequency augmentation in VIA Apollo KX133 doesn'thave the desired effect: memory bus throughput is still lower than that of the system bus.

That's why the most well-balanced chipsets for AMD Athlon ensuring the highest performance will be those supportingDDR SDRAM.

DDR SDRAM technology provides data transfer on both signal edges and provides 1.6GB/sec and 2.1GB/sec memory subsystemthroughput at 100MHz or 133MHz carrier frequency correspondingly. VIA and AMD Athlon chipsets with DDR SDRAM support willhit the market somewhere in the beginning of autumn, and in the meanwhile we have to be content with standard PC133 SDRAMsupport of KX133.

It's necessary to add, that VIA Apollo KX133 supports up to eight memory banks, which means that in theory it ispossible to design a mainboard with up to four DIMM slots. AMD 750 in its turn supports only 6 banks and 3 DIMM slots.Even in the aspect of supported memory VIA left AMD's chipset behind.

The third main advantage of VIA Apollo KX133 compared to AMD 750 is AGP 4x mode support. Here we would like to drawyour attention to the fact that many graphics cards, particularly those based on NVIDIA GeForce256 chip, were unable towork even in AGP 2x when used with AMD 750 based mainboards. There should be no problems like that with KX133. AGP 4xmode should provide a quicker texture transfer through the AGP bus, supported by all modern graphics accelerators. Stillas practice shows, not all modern applications are ready to fully use the power of AGP 4x mode, although the situation isvery likely to change when DDR SDRAM is applied in systems because now memory throughput is at best equal to that of AGP4x. And it is not only the processor and PCI-devices that work with the memory apart from AGP.

VIA Apollo KX133 chipset has a classical architecture and is composed of two chips: the VT8371 North Bridge and theVT82C686A South Bridge that are linked with a PCI bus:

We have already discussed the main features of the North Bridge above. There is only thing left that is worth mentioning: arather standard for all modern chipsets support of five PCI Master devices.

As to the South Bridge, it's the same chip we got familiar with in VIA Apollo Pro133A Review, a chip supporting 4 USB ports,2 UltraDMA/66 channels, an AC'97 link for AMR slot and AC'97 codec support, I/O ports, ISA bus and hardware monitoring. UnlikeVIA, AMD 750 South Bridge doesn't support AC'97 link and hardware monitoring. However, several manufacturers, such as ASUS andFIC for instance, used a South Bridge from VIA, VT82C686A, in their AMD 750 based mainboards.

In conclusion, we would like to bring your attention to the following comparative table of main features of AMD 750 and VIAApollo KX133 chipsets:

Anyway, the main objective of VIA Apollo KX133 is to throw into the market a large number of low-cost mainboards for AMDAthlon. Fester, the reference design of an AMD 750 based board, implies a six-layer printed circuit board layout. This leadsto serious difficulties during mainboard manufacturing because compound six-layer PCBs are more expensive and mainboards basedon them feature relatively low stability. Moreover, far not all the mainboard manufacturers have special equipment to producethem. KX133 based mainboard reference design implies a four-layer PCB, which gives us every reason to expect a mass productionof mainboards based on this chipset by both: big and small manufacturers.

Specification

The mainboard is supplied in a specially designed green box. The package also includes a set of FDD, UltraDMA/33 andUltraDMA/66 cables, several spare jumper caps, a retention mechanism for processor fastening and a bracket with twoadditional USB ports that can be installed at the rear of the PC's case instead of the expansion card. Apart from this,the box also contains a CD-disk with the drivers, ASUS PC Probe monitoring utility, and Trend PC-cillin antivirussoftware; a "Powered by ASUS" sticker with a Pegasus and a detailed user's manual.

Closer Look

Designed for AMD Athlon processor, ASUS K7V is equipped with Slot A. On the one hand, this shouldn't cause any trouble,because currently all Athlons are designed for this particular slot. But on the other hand, we shouldn't forget about theupcoming new Duron (Spitfire) and Thunderbird based CPUs. Their distinguishing feature will be L2 integrated on-die cache.This means that Athlon processor boards with soldered L2 cache chips won't be needed anymore. As a result, AMD will have tocease Slot A processor manufacturing and turn to Socket A based 462-pin ones in order to reduce production costs. Althoughthere's a Slot A version of Thunderbird in AMD's plans, its production is very unlikely to last long. As to Duron (Spitfire),it will be designed only for Socket A. The situation with Slot A-to-Socket A converters is rather intricate. What we can sayfor sure, is that these converters won't be widely spread on the market, like Slot 1-to-Socket 370 ones, if they appear at all.So, when buying a Slot A mainboard, ASUS K7V for instance, you must bear in mind that it may turn out impossible to use it withSocket A form-factor processors of the near future, such as Duron (Spitfire). However, there are no mainboards for Socket A inthe market right now. Besides, VIA chipset for Socket A - Apollo KZ133 - also is not announced yet.

The mainboard has three DIMM slots, allowing a total of 1.5GB SDRAM memory for ASUS K7V. As on VIA Apollo Pro133A chipsetbased mainboards, BIOS on ASUS K7V allows setting SDRAM memory frequency to 100MHz or 133MHz. Theoretically VIA Apollo KX133chipset allows clocking the memory even to 66MHz, ASUS engineers however considered this feature unnecessary and didn'tinclude it in BIOS Setup. Nevertheless, both PC100 SDRAM, and PC133 SDRAM users won't have any problems with K7V. Of course,you will get a slightly higher performance with 133MHz SDRAM. Talking about memory, it's necessary to mention the support of arather exotic VCM SDRAM, a buffered multi-channel version of PC133 SDRAM, currently manufactured only by NEC.

Like all recent ASUS mainboards, K7V has two ways of setting the processor frequency. You can switch between them with aspecial jumper. The first way is a jumperless one when the system bus frequency is set in BIOS Setup. The second way is via aset of four dip-switches located in front of the DIMM slots. The clock multiplier of AMD Athlon is locked in the processor (itis defined by the locations of some elements in the processor cartridge), that's why ASUS K7V has no means of changing thissetting.

	VIA Apollo KX133	AMD 750
North Bridge	VT8371	AMD 751
FSB	100MHz DDR	100MHz DDR
Memory	PC100/PC133 SDRAM	PC100 SDRAM
Max. memory size	2GB	768MB
Max. memory banks	8	6
AGP	1x/2x/4x	1x/2x
Number of PCI Masters	5	6
South Bridge	VT82C686A	AMD 756
ATA interface	UltraDMA/66	UltraDMA/66
AC'97	+	-
USB ports	4	4

Let's take a quick look at the AGP slot of K7V. After ASUS P3C2000, K7V is the second mainboard to be equipped with an AGPPro slot. Although this slot has a larger number of pins than a standard AGP slot it is fully compatible with general AGP 1x/2xand 4x graphics cards. To cut a long story short, its difference from the usual AGP 2.0 slot lies in additional pins for 12V and3.3V power circuits added to the ordinary AGP slot. They are supposed to satisfy the growing power consumption of the graphicscard, so that to provide up to 110W. From a practical point of view, AGP Pro slot on K7V mainboards allows using some NVIDIAGeForce256 based graphics cards with 64MB memory. To avoid incorrect installation of standard AGP graphics cards into aslightly longer AGP Pro, its first 20 pins, which are not used by ordinary graphics cards, are blocked with a special safety tab.

ASUS K7V has a rather unusual number of expansion slots: 5/0/1/1 (PCI/ISA/AMR/AGP). In other words, to some users'great disappointment, there are no ISA slots on K7V. Although this configuration meets the PC99 specification, old ISAdevices are still used sometimes. Full-size expansion cards can be installed in any of the five PCI slots. The fourthand fifth PCI slots use the same IRQ.

ASUS K7V uses VIA 686A chip for the South Bridge. One of its features is the implementation of a software-based AC'97 soundcard with the help of a Cirrus Logic CrystalClear SoundFusion CS4299 codec boasting all the basic features. Although softwaresound takes up to 10% of processor resources, it allows reducing the system cost due to no need in a separate sound card. Forusers who don't want to sacrifice system resources or want to have a better sound quality by using a separate PCI sound card,ASUS K7V allows disabling AC'97 sound both via BIOS Setup or with a special jumper. In theory, K7V has a special layout for anintegrated PCI sound controller from Aureal, but there are no mainboards produced with it currently.

As to the overall design of the mainboard, we found several problems here. For example, the DIMM slots are situated so closeto the AGP slot, that an installed graphics card blocks the DIMM slots clips. This means that in order to install or replacememory modules you will have to remove the graphics card from the AGP slot. Moreover, ASUS K7V's depth slightly exceeds theusual dimensions: standard mainboards are 3-4cm shorter. This means that you may face some problems when installing K7V intoseveral cases, so you should always bear in mind the size. Other than that, there are no more comments: FDD and IDE connectors,as well as the power supply connector are situated where they, actually, should be according to the ATX specification - in frontof the DIMM slots. This is a particularly nice thing, taking into account that ASUS's previous Slot A mainboard, K7M, had itspower connector situated between Slot A and DIMM slots. This disposition not only hindered air circulation near the processorheatsink, but also didn't allow using larger heatsinks needed for extreme overclocking.

The chipset's North Bridge is equipped with a small heatsink. On the board near AGP slot there is a green LED, whichgives visual warning if the PCI slots are powered. The LED serves to prevent the users from installing/removing PCI deviceswith the power on. We have to stress that connecting this LED to PCI power supply lines seems more correct than to memorypower supply lines, which is usually used on other mainboards. The matter is that according to PCI 2.2 specification, PCIslots are powered even in standby mode, i.e. when power to system memory is cut off.

Since the 100MHz DDR EV6 bus requires some particular signal quality, the capacitors used in K7V are larger than those,which we usually see on mainboards for Intel processors. They include one 4700uF capacitor, nine 1500uF ones and a pair of680uF ones, situated near Slot A. Besides this, ASUS resorted to one more stability improving trick (not quite an honest one)in its K7V as well as in all other mainboards: increase of memory, chipset and AGP voltage. The default voltage on the ASUS K7Vmakes 3.4V instead of the nominal 3.3V. Nevertheless, ASUS decided to take the risk with its K7V mainboard and left on it a jumperthat allowed changing voltage to a standard value. By the way, we wished they had never done this. At 3.4V voltage on I/O circuitsASUS K7V operates impeccably, demonstrating high stability and reliability, but at the official 3.3V voltage the mainboard'sstability leaves much to be desired.

ASUS K7V BIOS is based on Award Medallion BIOS v6.0 and has an interface similar to that of Phoenix's BIOS. Among theavailable Setup settings you can find manual assignment of IRQs to PCI slots, multiple memory timing settings, AGP 4x andFastWrites mode enabling/disabling function.

Although VIA 686A South Bridge of ASUS K7V has built-in hardware monitoring functions, ASUS engineers decided not to usethem. They probably did it because they wanted to control a larger number of sensors than the South Bridge allowed. That's whyASUS engineers applied their own ASIC ASUS AS99127F chip for monitoring. As a result, the mainboard can monitor: threetemperatures (one mainboard temperature and two other, measured by sensors attached to corresponding on-board connectors),the rotation speeds of three cooling fans (with a total of four cooling fan connectors available on the board) and sixvoltages. K7V also supports a chassis intrusion detector. Unfortunately, external temperature sensors are not included inthe package, which means that K7V doesn't allow processor temperature monitoring by default.

Overclocking

EV6 system bus used in AMD Athlon systems isn't very overclocking-friendly. As data is transferred via this bus at 200MHz,the slightest increase in this frequency can provoke serious worsening of the overall system stability. That's why the bestway of AMD Athlon overclocking is to change the processor clock multiplier. However, this procedure is not mainboard-dependentand is implemented by soldering over several elements on the processor board or by connecting special devices to the processortech connector. Thus, talking about overclocking possibilities of AMD Athlon mainboards you should regard them as purelytheoretical, since they are unlikely to be put into practice.

That's why you shouldn't be very enthusiastic about 24 FSB frequencies that can be set on K7V: 90, 92, 95, 97, 100,101, 103, 105, 107, 110, 112, 115, 117, 120, 122, 124, 127, 130, 133, 136, 140, 145, 150 and 155MHz. Probably you willhardly be able to make use of these great overclocking possibilities.

As to changing the processor voltage, ASUS K7V allows this, too. The voltage can be changed manually in an intervalbetween 1.3V and 2.05V range with a 0.05V step. That's why if you don't want to use the default setting for some reason,you won't need to make much effort to burn the processor by supplying a higher voltage. Moreover, the mainboard has ajumper that allows supplying up to 3.56V to AGP, memory and chipset.

Performance

As ASUS K7V is the first VIA Apollo KX133 based mainboard that has passed through our test lab, let's take a moredetailed look at its performance than we usually do. The following results will show all the powerful advantages of VIAApollo KX133 thanks to the support of such features as AGP 4x and PC133 SDRAM memory.

We compared performance of ASUS K7V based system with the performance of the same system built on a AMD 750 based ASUSK7M mainboard.

ASUS K7V was tested in two modes: with PC133 SDRAM memory and with PC100 SDRAM memory. Tests on ASUS K7M were alsorun in two modes: with SuperBypass option enabled and disabled. Enabling SyperBypass feature in AMD 750 based systemsallowed reducing memory subsystem latency by 25% although in the first chipset revisions this option was implementedincorrectly and didn't work.

As you can see from the results of this test, VIA Apollo KX133 based ASUS K7V is approximately 7% behind AMD 750based K7M. The situation couldn't be ameliorated even with PC133 SDRAM memory used in K7V based system. The mostprobable explanation of this confusing situation with KX133 can be the fact that this chipset isn't that optimizedfor the work with CPU L2 cache, which fastness directly influences the performance in business applications. However,this issue will probably be corrected in new BIOS versions.

Although a similar test also measures system performance in business applications, it shows a much smaller lag ofASUS K7V. In fact, we think it will be very difficult to notice the performance difference when working.

Let's take a look at the results shown by VIA Apollo KX133 in gaming applications:

High Quality mode in Quake III is an ideal situation for AGP 4x advantages testing, because in this mode the AGP busis loaded with work to the maximum. We can see that K7V in AGP 4x mode easily surpassed by more than 6% K7M operating inAGP 1x mode (AMD 750 based mainboards are unstable in AGP 2x mode with NVIDIA GeForce256 based video cards that's why theexisting drivers use AGP 1x only).

With these settings CPU speed comes to the foreground instead of AGP bus bandwidth. This is why in this test K7M and K7Vshowed approximately the same results.

Unreal Tournament is a very resource-eating game. Due to special features of its gaming engine, the fps rate doesn'tdepend that much on the CPU and graphics card performance. That is why we can observe almost the same results on bothmainboards, though AMD 750 with SuperBypass enabled is still slightly ahead.

There are no particular differences compared to the previous diagram: both mainboards operate practically in the sameway. However, this test was carried out at a higher resolution, which produced additional AGP overloading and as a result,VIA Apollo KX133 turned out a little bit ahead.

A similar situation: both VIA Apollo KX133 and AMD 750 based mainboards show the same performance despite the fact thatoverall performance in Expendable depends a lot on memory subsystem performance.

Once again we have to mention that at high resolutions ASUS K7V based system performs better although this advantage is sominimal that it's almost imperceptible.

Totaling the test results we must say that VIA Apollo KX133 chipset showed nothing revolutionary in terms of performance.In fact, its advantages can be seen only in 3D-games and only at high resolutions.

Conclusion

First of all a few words about VIA Apollo KX133. Although this chipset has a lot of new features for Athlon based systems(such as AGP 4x mode and PC133 SDRAM memory support), these advantages are almost unnoticeable in real applications. Moreover,in many cases AMD 750 with SuperBypass feature enabled provides even a slightly higher performance level than VIA Apollo KX133.However, KX133 aims at a bit different things. Its goal is to provide the market with a large number of low-cost four-layer SlotA mainboards, and this goal will probably be achieved.

Now about ASUS K7V. It's doubtful that this mainboard can be considered as something revolutionary but still it's a goodaverage product with all modern features.