Try and avoid an architecture that has a mixture of more than two I/O buses, such as ISA, PCI, and VLB, for your server. While these platforms offer the ability to use more types of peripherals on a single computer, they usually do not perform as well. It is much better to choose a platform with a dedicated ISA/PCI or ISA/VLB bus and use the faster bus for your video, disk, and network adapters.

Aside from your processor and I/O expansion bus, you should take into consideration a few motherboard issues before making your final purchasing decision.

A Few Motherboard Considerations

This section addresses a few motherboard considerations that you should look into before making your final purchasing decision. First, consider the primary memory subsystem, as Windows NT Server uses it quite heavily. Secondly, consider the memory caching subsystem, as the type and size of the cache affect the primary subsystem’s performance. Not only will these two items play a very important role in the overall performance of your system, but they will also impact your future upgrade decisions. The following sections discuss how you can choose the best primary memory and memory caching subsystems.

Choosing The Best Primary Memory Subsystem

Your primary memory subsystem is one of the most critical choices you can make for your computer system. This choice can be divided into three component areas:

•  Type of memory used

•  Memory speed

•  Amount of installed memory

In the early days of personal computing, there was only one type of computer memory used in the computer’s primary memory subsystem. This has changed tremendously over the years. Today, you can find computer systems that utilize any of the following:

•  DRAM (Dynamic Random Access Memory)—This is the least expensive memory used in today’s computers and has been around the longest. All the bugs have been worked out of this technology. Its only drawback is that it is not the fastest memory to use in your computer system.

•  EDO RAM (Enhanced Data Out Random Access Memory)—This memory is more expensive than DRAM, but it offers an additional performance increase of up to 20 percent. Systems that use an EDO RAM memory subsystem generally cost between $100 and $200 more than a comparable system that uses a DRAM-based memory subsystem.

•  SDRAM (Synchronous Random Access Memory)—Today’s memory king is SDRAM, which provides for improved memory performance by enabling access to data in a more orderly fashion. SDRAM costs about 50 percent more than DRAM, but it may be worth it for the improved system performance.

When making your purchasing decisions, choose SDRAM over EDO RAM and DRAM if you have the budget. Otherwise, choose an EDO RAM-based system over a DRAM-based system. As a last resort, choose a DRAM-based system.

Memory type isn’t everything, however. All memory has a speed rating that determines how fast the memory can be accessed. This speed is measured in nanoseconds, where one nanosecond is one billionth of a second. Currently, memory speeds fall between 10 and 200 nanoseconds. Memory with speeds below 30 nanoseconds is generally used by the caching subsystem (more on that in the next section) while memory used in the primary memory subsystem falls between the 60 and 80 nanosecond range. When it comes time for you to purchase memory for your computer, you should purchase the fastest memory possible. If your computer system can use memory between 60 and 80 nanoseconds, then choose the 60-nanosecond memory. Be sure, however, that all of the installed memory is the same speed. It does you no good to install faster 60-nanosecond memory in a computer with 80-nanosecond memory already installed.

To take maximum advantage of the faster memory, you may need to configure the number of memory wait states in the system BIOS. A wait state is the time the processor must wait before accessing the same memory location. Faster memory can utilize a lower number of wait states than slower memory and improve overall system performance.

The minimum memory requirement for Windows NT Server is 16MB of RAM, but this is just the bare minimum required to get the operating system installed. A more realistic figure is 32MB of RAM for a basic network file server, and I usually recommend a minimum of 2MB of RAM for each additional system component (Services for Macintosh, Gateway Services for NetWare, Striped Sets with Parity, and so forth) you install. I also recommend an additional 16MB of memory for each additional BackOffice component (SQL Server, System Management Server, Exchange Server, and so on) you install on the server. Depending on your performance requirements, you may need even more memory. For what it’s worth, my primary domain controller has dual Pentium 166MHz processors and 128MB of DRAM. It has all the BackOffice components installed, except SNA Server, and it performs quite well.

Any type of installed memory is better than using virtual memory on your server. Virtual memory is memory that does not physically exist. A portion of your hard disk is used instead to store information that would normally be stored in physical memory. If you consider the fact that memory speeds are measured in nanoseconds and disk speeds are measured in milliseconds (thousands of a second), you can understand that using virtual memory can slow down your system tremendously.

If you have an EISA-based computer, make sure the EISA memory setting (based on the EISA setup utility disk application) correctly identifies the amount of physical memory you have installed in your system. If it does not, Windows NT will use the ISA setting (what it finds based on the BIOS setting), which may limit the amount of memory that Windows NT will use.