Performance Upgrading: A Look at IBM PS/1 486 Computers (When and What to Upgrade in terms of Memory, Processor Cache, and Processors) Upgrading the computer is virtually an inevitable step in today's state of technological flux. What is today's power computer quickly becomes tomorrow's sluggish beast... or does it? Many techno-writers have placed an emphasis on the high-dollar, high-speed performance machines as the "must have" computer of the day, consequently leaving their readers with a sense that their current machine is useful only as a large doorstop. However, in most cases, simply upgrading the computer in an efficient manner brings about the results that the user requires, thus saving time, money, and wasted technology on something which may not effectively address the needs of your computer. This article is designed to help determine if your computer needs to be upgraded, when it should be upgraded, and how it should be upgraded in the most efficient and cost-effective way. The Stuff Computers are Made Of ------------------------------- In today's operating environment (DOS, Windows, OS/2, and UNIX, for example), there are many factors which could influence a computer's performance. Often times, after a period of use, users discover that their computer is just operating too slowly for their preference. The end results sometimes is a processor upgrade, which may not necessarily create the desired effect. An understanding of what causes the slowdown and, in turn, how to correct this speed decrease is important in efficiently and inexpensively speeding up your computer. The most important elements of computers for speed purposes rely on (in no particular order) the processor speed, RAM, processor cache, video graphic performance, and hard drive performance. In some instances there is a certain degree of freedom in upgrading these elements, but it is important to know which parts affect your computer's performance. Granted, upgrading only one of these elements will inevitably produce results, but if your performance problems lie in one specific area the upgrade you have chosen may not have produced as dramatic an effect as you were intending. The processor is the "captain of the ship", and is responsible for all the actions in the computer. Certainly, the faster the processor the faster the computer will perform. Speeding up the processor will always speed up the entire computer. However, there are many instances in which increased processor speed may not help as much as a prior upgrade of one of the other elements. RAM (Random Access Memory) is in charge of holding information for the applications that are currently active. In other words, if you are running Windows and Program Manager is active, RAM is storing information about Program Manager and anything you are immediately doing for quick retrieval. Without RAM, no applications could be executed. However, RAM plays a slightly altered role under Windows or OS/2. These operating systems both reap benefits from having a large amount of RAM, which allows them to load more components and more applications simultaneously for fast retrieval. However, both these environments support the use of a swap file, which is an allocated amount of disk space that emulates RAM. In any specific situation, if RAM is completely filled, Windows and OS/2 will write information to the hard drive temporarily in order to shuffle enough free RAM for the program to work. However, because the hard drive writes information much more slowly than RAM, time is wasted when using the swap file versus using regular RAM. Processor cache works as an intermediary between the processor and RAM, allowing information to be passed from a fast processor to relatively slower memory chips efficiently. When the processor gets called, it sends its results directly to a slightly slower processor cache for it to distribute to the even slower RAM. By allowing a buffer between the processor and the RAM, the processor no longer has to wait on the slow RAM to handle the incoming information and can be free to work on more processes while the cache stores the information and disperses it when RAM is ready. Video graphic performance is important for today's graphical environments (such as Windows and OS/2). The need for speed is increased even further when graphical applications such as AutoCAD, Corel Draw, and Aldus PageMaker are introduced on the system. Chipsets generally consist of non- local bus and local bus varieties. Of the two, local bus is more faster because it operates at the local bus speed (usually either 20 MHz, 25 MHz, or 33 MHz depending on the computer). In contrast, non-local bus video systems operate at 8 MHz, the standard set by the IBM PC/AT for 16-bit adapter cards and system boards. Many users, considering the system bottleneck to be in their system's local bus video, purchase an ISA (Industry Standard Architecture, or AT-bus) video card as a replacement, which actually slows down video performance as the video card communications with the computer at the AT-bus, non-local bus speed of 8 MHz. Some of today's newer video cards can overcome this limitation somewhat by using advanced VRAM and processing, but their is no comparison to local bus speeds of 33 MHz. Hard drive performance is the final element of a computer's performance, which is further complicated by the recent introductions of enhanced IDE and SCSI-2 hard drives. Hard drives are made up of cylinders and heads, and the more cylinders and heads the larger and faster a hard drive will be. IDE (which stands for Integrated Drive Electronics or Intelligent Drive Electronics) was originally defined as hard drives with 16-bit communication (in accordance with the AT standard) to the processor and a 1024 cylinder limitation in size. Using the maximum number of physical heads on a 3.5" IDE drive (16), 1024 cylinders equated to about 528 MB. IDE drives also have a seek time and throughput level, which indicate performance. With standard IDE drives, seek times usually average about 12 ms while throughput typically measures about 2 MB / second through a fixed 16-bit hard drive controller. However, with today's new enhanced IDE drives, the standard IDE definition limiting the throughput, non-local bus communication, and number of cylinders has been rewritten. Enhanced IDE drives can now allow for local bus 32-bit controllers, up to 8 GB per physical drive, and throughput reaching 10 MB / second. Although seek times have dropped somewhat, the speed increases brought about by the enhanced IDE changes have greatly improved the way in which disks are managed. However, because hard drives and controllers are generally limited in their expansion abilities, it is not always feasible or possible to upgrade to enhanced IDE capabilities on existing computers and this subject will not be elaborated upon further in this article. How do I Determine Which Upgrade is Right for My Computer? --------------------------------------------------------- Determining which part will produce the greatest effect is simply a matter of recognizing where the slowdowns on your computer occur. Ask yourself these questions (and they assume that only graphical environments such as Windows and OS/2 are running when the slow-downs occur): - Does the slowdown occur when my applications are first starting or whenever the hard drive is working? - Does the slowdown occur when my applications are working, such as when my graphics program is drawing or my spell-checker is checking? These two questions generally provide the core of all upgrading considerations, and deciding which upgrade should be made can generally be extrapolated from the answers to these questions. If your answer to the first question is "Yes", then most likely the upgrade needed relates to either the RAM or the hard drive performance. A tell- tale sign is if the hard drive is accessed a significant amount of the time while launching or using your program. This usually indicates a shortage of RAM because Windows or OS/2 uses the swap-file technique described previously to compensate. Many users incorrectly determine that the bottleneck is caused by a slow processor, when in fact the lack of RAM is forcing the computer to use hard drive space in order to execute the program at all. For many of today's applications, including more powerful word processing programs such as Word Perfect and Microsoft Word, 8 MB of RAM has quickly become a minimum. If 4 MB is present on your computer, an upgrade to 8 MB or more will provide one of the greatest increase in speed and a more efficient upgrade than any other upgrade. Hard drive performance, if it can be increased on the computer, will certainly improve speed as well in these instances. However, the goal is to access the hard drive as little as possible since the hard drive is by far the slowest element of a computer (even with the enhanced IDE performances increases). Speeding up the hard drive is therefore not as efficient as avoiding its use altogether. With as little as 16 MB of RAM, it is possible to never access the swap file and keep launch times to a minimum (although for Windows and OS/2 it is recommended that at least a 1 MB swap file be maintained). If your answer to the second question is "Yes", then the necessary upgrade is most likely processor, processor cache, or video performance related. Although there can be exceptions (such as if the hard drive is working hard during the spell-checking or graphics displaying), these upgrades are usually one of the most desired. What becomes difficult to determine occasionally is just which of these three elements is the limiting factor. However, there are some general guidelines that help make this determination. First, if the processor operates at 25 MHz or slower, processor cache is not needed for speed increases. This is not to say that processor cache would not help a little, but it does mean that speed gains are minimal when compared to faster processors. For 33 MHz and 50 MHz processors, at least 128 KB of processor cache is recommended. For 66 MHz processors and faster, 256 KB of processor cache is desired. In other words, if you have a DX2 / 66 MHz computer, 0 KB of processor cache, and you answered "Yes" to the second question, the first upgrade you purchase should be processor cache. Speeding up the processor first will only make the processor wait more for the RAM. One of the biggest misconceptions, however, is video speed. Many performance-checking programs report video performance as being sluggish, suggesting that video drivers and even video chips be improved (even on local bus video computers!). However, generally the culprit is a slower processor. A processor boost will usually provide significant speed increases to video functions. As a general rule, if you suspect that the video is operating slowly and you already have local bus video capabilities, chances are the processor should be upgraded to 66 MHz or better (or Pentium technology, if available... more on processor specifics a little later). The video improvements realized by a faster processor should be significant enough to appease most performance-checking utilities. SX2, DX2, DX4, and P24T OverDrive Upgrades: ------------------------------------------ If it is determined that a processor upgrade is needed, there are currently many options available for most computers. OverDrive processors, offered by Intel Corporation, usually provide an inexpensive alternative to replacing the computer altogether. However, there are many OverDrive options available, and determining which is right for you depends on the applications you use. What are the differences between all the OverDrive options? There are currently four different versions of the OverDrive processor: an SX2, DX2, DX4, and P24T OverDrive. There are numerous differences between each of these processors. Namely, the SX2, DX2, and DX4 processors are a part of the Intel 486 family of processors, whereas the P24T belongs more to the Pentium family despite the 32-bit I/O structure. Let us take a processor-by-processor look at each of these OverDrives: Intel SX2 OverDrive: The SX2 OverDrive is available only for 20 MHz and 25 MHz computers. It allows the processor to operate at twice the bus speed. For the aforementioned computers, the processor would run at 40 MHz and 50 MHz, respectively, while the system bus speed remains at its 20 MHz or 25 MHz. The SX2 OverDrive is the least expensive of all the OverDrive options (street price of around $130), primarily because of the lack of a math coprocessor. However, the combination of clock-doubling and low price make the SX2 OverDrive ideal for consumers who desire increased processor speed yet do not have the need for floating point calculations allowed by a math coprocessor. Intel DX2 OverDrive: The DX2 OverDrive functions identically to the SX2 OverDrive with a few exceptions: it contains a math coprocessor for floating point calculations and it is available for 33 MHz computers as well as 20 MHz and 25 MHz computers. The current street price for the DX2 OverDrive is about $200. Intel DX4 OverDrive: The DX4 OverDrive, despite its name, acts as a clock-tripler with a math coprocessor. However, architecturally it differs from its DX2 and SX2 siblings by using a lower voltage requirement (3.3 volts versus 5 volts). Since this poses a problem in connecting to today's current 486 systems, Intel has released a DX4 OverDrive version which contains a voltage converter to allow the 3.3 volt chip to operate with existing 5 volt sockets. Working with current 25 MHz and 33 MHz systems, processor speeds can be increased to 75 MHz and 100 MHz, respectively. Street prices for the DX4 OverDrive are about $350. Intel P24T Pentium OverDrive: The recent release of the P24T Pentium OverDrive processor has brought Pentium technology to existing 486 platforms. Operating at a 5:2 processor- to-bus speed ratio, the P24T allows faster processor power at a lower MHz rating. For example, for a 25 MHz computer the P24T will operate at about 63 MHz. Likewise, current 33 MHz computers will power the P24T at 83 MHz. By processing more instructions per cycle, an 83 MHz P24T can process faster than a 100 MHz DX4. The current list price for the P24T Pentium OverDrive is about $550. The 63MHz Pentium OverDrive is currently available from Intel, while the 83 MHz P24T version is scheduled to be released at a later date. Which upgrade is right for me? As with most similar questions, the answer depends on the goal of the computer's use. As a guide, ask yourself these questions: - Will the computer be used for intense calculations or graphical work? - What operating environment does the computer typically use (e.g. DOS, Windows, OS/2, UNIX, etc.)? - Are the applications resource intensive? - What are my needs now, and how may they change in the near future? For intense graphical and mathematical applications, a fast processor and much RAM is needed. In these cases, the P24T with about 16 MB of RAM is probably desired. On the other hand, if the computer is mainly used for less intensive work and mathematical abilities are limited, the SX2 OverDrive is a more cost-effective solution. The right combination of speed and price can only be determined by you. As previously mentioned, you may determine that your 33 MHz computer would serve best from an 8 MB upgrade, adding 256 KB of external cache, and putting a DX2 OverDrive to boost the speed to 66 MHz. On the other hand, if you own a 25 MHz computer, an SX2 OverDrive with another 4 MB of RAM may suffice if you use lighter applications. Processor Cache Upgrades: ------------------------ Most computers of 33 MHz bus speed or higher can accept at least 128 KB of processor cache. This cache can be added in groups of four chips (128 KB per set of four) and a tag module. Current street prices allow for about $0.45 per kilobyte of cache, and many local and mail-order computer dealers carry this cache. RAM Upgrades: ------------ All IBM PS/1 486 computers can be upgraded to at least 32 MB of RAM, and some as high as 64 MB. However, maxing the RAM upgrade is something that is generally not necessary, even for today's applications). In fact, DOS itself can only recognize 16 MB of RAM total. The maximum RAM upgrades then will usually last for years to come. However, it is important to purchase the right kind of memory for your computer. Some computers take gold while others take tin. some require 30-pin SIMMs in groups of four identical SIMMs while others require 72-pin SIMMs that can be added one SIMM at a time. Still more require parity SIMMs while others need non- parity SIMMs. Check the Answer Bank for memory specification, or ask your IBM technician on the Info Exchange which type of memory is required for your computer. Conclusion: ---------- Upgrading the computer for the optimal results can be a difficult decision. However, it is imperative that you ask yourself what type of speed increases are desired in order to utilize the best upgrade for your needs. If you have any questions regarding upgrading your computer, feel free to post a question on the IBM Club Info Exchange of PRODIGY, the IBM Connection Info Exchange on America Online, the IBM PS/1 forum on Compuserve, or on the IBM PS/1 BBS. 486 Upgrade Compatibility for U.S. IBM PS/1 Computers: ----------------------------------------------------- Complete test results on model-specific supported and non-supported Intel DX2 / 66 MHz OverDrive processors and non-supported Intel DX4 / 100 Mz OverDrive processors can be found in the OD-TEST.TXT file, located in the IBM download section.