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| AMD MPX Production Boards ASUS A7M266D vs. MSI K7D-L vs. Tyan Tiger MPX: Dual Power at 1900+ | ||
| (Review by MS, March 11, 2002) |
Do's and Don'ts of the MPX chipset
After the release of the MPX chipset, a few things have started spooking around, regarding what the MPX chipset can do and what it can't.
Yes and No! There is a slim chance that one or the other USB device will not function properly, chances are in the order of 1/1000 or lower that this will ever happen for a home / workstation user. On the other hand, in order to pass validation by AMD who are concerned with 100% functionality of the MPX boards as a server platform, the USB ports need to be disabled. However, this is a BIOS issue and does not reflect hardware functionality per se. We tried it and have more results on this later.
There is more to that story than meets the eye!. What it comes down to is a mixture of parameters that define whether the system will run games based on the Quake3 Arena engine in MP Mode. In general, using older MP processors, the problem hardly surfaces. For example, using the Athlon MP 1200, and an older Radeon AIW (R100 core) there were no problems at all. Likewise, with the GeForce3 using the 12.41 drivers, there were no issues with Quake3 Arena. Problems started with upgrading to higher speed grade processors, that is, with the MP 1900+, Quake3 Arena would no longer run at the Fast and Fastest setting. Likewise, using a Ti 500, which requires drivers 21.81 or higher in order to be recognized correctly causes Quake3 Arena to crash if SMP is selected. A similar behavior shows up with the ATi Radeon 8500.
There are a few possibilities and workarounds to make Q3A work in SMP mode that may or may not work depending on the system configuration. In most cases, the failure is related to lower resolution, that is at the Normal setting, at least the GF3 is working in most cases. One trick that can be used is to enter the r_smp 1 command to activate SMP mode but to revert to the r_smp 0 mode before exiting the game. Officially, SMP mode requires restarting of Quake3 Arena however, we found an increase in frame rates from 220 to 260 fps at the Normal setting with the GF3 which we can only explain if, in fact SMP mode was initiated.
With the Ti500 things are somewhat more complicated in that the game develops a tendency to freeze as soon as the SMP command has been entered. If it doesn't freeze immediately, one just needs to try and change the display settings and the system will hard-lock.
There are some registry hacks for Win2K and XP, that have been posted by nVidia involving "regedit" to add the DWORD PushBufferSpace and set it to 1. We tried, and it doesn't work. With the GF3, selecting 2 x AntiAliasing solves the problem, however this setting is not really suitable for system benchmarking since the graphics card becomes the limiting factor. Still, it worked at 640 x 640 x 16 bpp or higher
With the ATI Radeon 8500, the situation is rather similar, only that in this case, the trick is to enable Anisotropic Filtering. When we used PowerStrip to disable subpixel accuracy, the system would freeze immediately after enabling SMP mode, a logical consequence of removing the data basis for Anisotropic Filtering and, thus, rendering it dysfunctional. Again, it won't work with all drivers and all CPUs but it can be done. Keep in mind that resolutions below 640 x 480 x 16 bpp will cause the system to hang.
We never saw these problems with the MP chipset in the original test configurations, however, the hardware used there was also two generations behind. Upgrading to the MP1900+ and a faster graphics card did exactly the same thing on an MP chipset as on the MPX chipset, that is, enabling SMP mode would either hang or else crash the system.
These issues affect all games built on the Quake3 Arena engine, that is Return to Castle Wolfenstein is even worse to get it to work in SMP Mode. Other OpenGL games with built in SMP support like MDK2 don't have a problem, though.
What it comes down to is one common denominator, that is, as long as the AGP card is the limiting performance factor, things will work. To rephrase, it appears as if the AGP needs to act as a throttle, otherwise the system will freeze.
Originally, the blame was put on nVidia, meaning that the latest driver revisions are too aggressive but then we find that, at least some of them work fine with the 1200 MHz CPUs. The next possibility is that Quake3 itself is somewhat buggy. There is a distinct possibility for this being true. The last possibility is that there is an issue with the 762 North Bridge but the only way to find out would be to run another high-end MP system and see what happens e.g. with a dual Xeon system running at 2 GHz.
It's the BIOS, Dummy! Most MPX boards use a BIOS string that will ask for the specific Athlon MP CPUID and if this is not present, the second CPU will not be initialized. On the other hand, most XP processors will work if they are put in as a matching pair. The same may or may not work with Thunderbirds or Durons which did work in SMP mode in the Tiger MP board. Keep in mind that it will depend on the BIOS revision of the board whether CPUs other than the MP will work in tandem so it is a bit of a gamble. If worst comes to worst, there is a chance to use WPCredit and WPCRSET to flip the "Who-Is" bit somewhere around Offset 80 to disable the disabling (I need to look a bit more into the settings before I can make a definite recommendatiom).
Yes but only if you need to use ECC! All MPX boards officially support up to two unbuffered DIMMs, inofficially, there are no problems with three unbuffered DIMMs either but the system stability is definitely better with registered DIMMs, especially under overclocked conditions, as paradox as this may sound.
With this out of the way, we can look at some of the honorable contenders. In general, all boards have a very similar layout featuring, as the name already indicates, two Socket A CPU interfaces. Another common feature is the presence of four DIMM slots, one AGP slot, two 64 bit PCI slots and three standard PCI slots, except for the Tyan Tiger MPX featuring four 32 bit PCI slots. All boards we are looking at also feature a standard dual IDE / UATA configuration and the legacy floppy connector. This is, however, where the similarities end since with everything else, the manufacturers have gone different ways.
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