PC/97 and the PA-2007

I have often said that the one aspect of this industry that I love is that things change so fast that there is always something new to learn, and that the one aspect of this industry that I hate is that things change so fast that knowledge becomes obsolete almost overnight.

The issue of PC/97 compliance has recently raised it’s head for us, and caused us to realize that our knowledge in this area was not complete and somewhat out of date. The specific circumstance that brought up this issue centered around the PA-2007 motherboard.

Recently, at least one vendor has updated their site to indicate that the PA-2007 motherboard they offer is using the VP2/97 chipset and offers PC/97 compliance. This prompted a few people to contact us and ask if the boards we offer also have this chipset and feature. To answer, we looked in three places: VIA’s website, FIC’s website and the PA-2007 manual. Our conclusion was that there is only one version of the VP2 chipset, and similarly only one version of the PA-2007 motherboard – both which offered PC/97 compliance.

Unfortunately, this was only partially correct, which a few emails from customers pointed out to us. This forced us to investigate a little further to find out exactly what the heck is going on

PC/97 Background

PC/97 is a hardware/software standard worked on by Microsoft, Intel, Toshiba and perhaps a few other companies in an attempt to eliminate some of the configuration and management issues that are present in Windows 95 (and to some degree in other operating systems). Requirements for PC/97 include ACPI (Advanced Configuration and Power Interface), Plug n Play support, USB support, IEEE1394 (firewire) support, UDMA/33 support, etc.

USB and IEEE1394 support is intended to provide hardware flexibility and extensibility. USB provides a slow to medium speed serial interface for keyboards, mice, etc. while IEEE1394 provides a very high speed serial interface for hard drives and other I/O intensive peripherals. The ACPI and PnP support is intended to make it easier for operating systems to query the hardware and have the correct drivers installed. It does this by having a standard way for each type of device to identify itself, including PCI, ISA, USB, IEEE1394, PCMCIA, etc. In addition, there are some power management features that can be taken advantage of via the operating system, rather than having to set them in the BIOS

The PC/97 standard was intended to be implemented in Windows 97, so chipset manufacturers began to produce chipsets that would conform to this specification early last year. The spec has undergone some revisions (as all specs do), and there currently are no operating systems that will take advantage of these features. The information provided to us is that full PC/97 compliance will not be available until the final Windows 98 release (we don’t know about the current beta release yet).

PC/97 and the PA-2007

Recent correspondence from both VIA and FIC have indicated that the VP2 chipset has two options: Full PC/97 compliance and Partial PC/97 compliance. What determines this is the VT82C586 South Bridge controller chip, which is identified with a suffix of either ‘A’ or ‘B’. A look at the data sheets page also shows both VP2 and VP2/97 documents.

After discussing this with FIC and reading the datasheets, the conclusion is that the VT82C586B South Bridge provides all of the PC/97 features to be considered fully PC/97 compliant, while the VT82C586A South Bridge lacks the ACPI support. However, in all other ways the two chips are functionally identical

It is our understanding that ACPI support is not fully implemented in the current beta of Win98, so there is currently no difference in function or feature set between the 586A and 586B with any OS available today. If anyone has information that is contrary to this, we would be interested in hearing about it.


In the final analysis, the issue of which South Bridge chip is on your motherboard will likely affect very few people – at least in the near term. If you have no intention of upgrading to Windows 98 for awhile, you will not be able to take advantage of the ACPI features in any case.

It is also very likely that the PC/97 spec (which may end up being renamed to PC/98) will be changed and not all chipsets/devices which are considered PC/97 today will be fully compliant by the time the final release of Windows 98 appears. In addition, since many of these features have yet to be fully tested, there is a strong liklihood that there will still be issues to resolve with those features that *are* included, perhaps even requiring a new chipset revision.

At this time, we believe that this is more of a marketing issue for most than any real concern. There are those, of course, who will be jumping to Windows 98 immediately and are currently installing each beta release as they appear. Even many of these people will not require the ACPI features unless they are changing and adding components fairly frequently (though some will desire the power management features). These days, many hardcore power users swap their motherboards every year or less anyway, so there is a reasonable chance that these individuals will no longer have the PA-2007 board installed by the time Windows 98 is finally released.

Right now, this issue is similar to the USB support issue that was raised two years ago. Customers were demanding that their motherboards support USB, and complained loudly when the support wasn’t included in their revision. Some even demanded that the manufacturer replace their board for free. In the end, USB devices didn’t appear for at least another year, and we still have very few available. Most of those who ‘required’ USB support still do not have USB devices.

While ACPI support is important to a few individuals today (mostly developers, we would guess) and may concern a percentage of people before the end of the year, the majority will gain no tangible benefit from the 586B South Bridge vs. the 586A South Bridge in regards to the PA-2007 motherboard. Before purchasing, consider what your needs are and base your decision upon reasoned choices that include price, service, support and product features rather than focusing on only one issue.

All things being equal, it is obviously best to have the ‘latest’ revision, however you should make sure that you are not gaining something you cannot use at the expense of losing something you *can* use, such as post sales support or good customer service.

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