Frequently Asked Questions Index:
1. Can you explain Fast Page/EDO RAM?
Reader: I wish to upgrade a Pentium 133 MHz rig having only 16MB of RAM by adding two 32MB 72 pin EDO SIMMS. I have noted some suppliers list these as Fast Page/EDO, quoting a speed in nanoseconds. Is this crucial? Computer Doctor: You should install the type of memory supported by your system, and most P133 systems (depending on the motherboard chipset) can use either FPM or EDO memory of a given speed (EDO is a little faster). You can normally install faster memory than is required, however you shouldn't install slower memory than your board requires. I recommend you purchase memory upgrades from http://www.crucial.com. They can suggest the proper memory guaranteed to work in your system. Note that FPM and EDO memory is obsolete, so don't be surprised if you have to pay more than double for that type of memory as compared to much faster modern SDRAM! In many cases I feel that it simply isn't worth installing expensive obsolete memory in otherwise relatively worthless obsolete PCs, opting for a motherboard/CPU/memory upgrade combination instead. 2. Will PC100 SDRAM work with a Pentium 4 processor?
Reader: I was wondering how long you think that PC100 SDRAM will be a current memory type? Do you think if I bought another 128MB SDRAM that I would be able to use it with a future CPU such as the Pentium 4 series? Computer Doctor: No, PC100 has just become obsolete as far as being "state of the art". Most newer systems today need either PC133 SDRAM, PC800 (RDRAM), or PC1600/PC2100 (DDR-SDRAM). The Intel 850 chipset (currently the only chipset for the Pentium 4) supports only RDRAM, however Intel and others are busy working on new chipsets that will support DDR-SDRAM. There probably won't be a Pentium 4 chipset that supports either PC100 or PC133 SDRAM since they are too slow for that processor. 3. Can I install PC133 memory in a system that requires PC66 or PC100 memory?
Reader: I am planning to upgrade my PC's memory. I currently have a 128MB PC100 memory module. I have one slot free. I want to get a 256MB module, giving me 384MB. Will Windows 98SE work with mixed-size memory modules? And, can I use PC133 instead of PC100 memory modules? Computer Doctor: Win98 SE will handle any memory that is compatible with your motherboard/chipset. And, you can use PC133 in place of PC100 or PC66 SDRAMs. Since PC133 modules are used in many new PCs, buying PC133 modules today allows you to reuse your memory upgrade in the future on new machines. That's why I have only been purchasing and installing PC133 memory in my systems lately, even for those that only require PC66 or PC100 memory. 4. Some of my DIMM sockets don't seem to working properly. Can you help me track down the cause of this problem?
Reader: I have a board with three DIMM slots. I have two 128MB PC100 tested DIMM modules. Either one works OK alone in slot 1, but they will not work together as 256K in any combination of slots 1 and 2 or 1 and 3 even though made by the same manufacturer. My system is using all current drivers, 300 watt power supply and good cooling. Do you have some possibilities I could test? Computer Doctor: Check these possibilities: Memory that's not really PC100-compliant. How do you know these are really PC100 memory modules? There is a lot of bad or counterfeit memory floating around, so if you didn't get these from a reputable source they could be suspect. Note that real PC100 modules require 8ns (8 nanosecond) chips or faster. Unless the chips have been remarked (which does happen) you can tell the speed of the chips by decoding the part numbers on them. Problems with your motherboard configuration. If your board supports memory timing parameters in the chipset setup screens in the BIOS Setup, then try resetting to factory defaults or in general slower settings. Also make sure your motherboard has the latest BIOS, and that it does support the type and size of modules you are installing (check the documentation). Defective PC100 memory. Replace your modules with known-good modules and retest. Defective motherboard. If you have known-good modules, the memory timing parameters are correct, and it still fails, then you probably have a bad board. Replace the motherboard with a known-good spare and retest.
5. How do current memory modules, such as PC100 and PC133, compare to PC66 modules in terms of nanoseconds?
Reader: I remember when memory modules were rated by nanosecond (ns) speeds such as 70ns, 60ns, etc. How do the current PCxx speeds such as PC100, etc. compare to ns speeds? I want to make sure that when a buy a so-called "PC133" module that its memory chips are the right speed. Computer Doctor: The current SDRAM standards are PC66, PC100 and now PC133. Note the speeds generally work out as follows: PC66 = 10ns (100MHz) PC100 = 8ns (125MHz) PC133 CL3 = 7.5ns (133MHz) PC133 CL2 = 7ns (143MHz) In other words, to be rated as a PC100 module, the chips will be rated 8ns, which technically equals 125MHz. PC133 CL2 (Column Address Strobe [CAS] Latency of 2 cycles) memory is generally rated 7ns, which technically equals 143MHz. 6. Can you explain the differences between segment addresses and linear addresses? Reader: Just for clarification: For IDE/ATAPI CD-ROM and tape drives, are their respective controllers on the devices itself or on the motherboard? Also, a book I read at the library mentioned that you must have an ATAPI driver when installing a CD ROM drive. Is this true? Computer Doctor:Unfortunately anything else I could reference is much more technical and even harder to understand! I often explain this further in the PC hardware classes I teach, but currently we are running them only for larger companies. The best analogy is to think of a hotel. Each floor can be thought of as a segment, and the room number on the floor is the offset. Thus room 541 would be segment 5, offset of 41. The confusion comes from the fact that both segment and offset overlap in the PC. So to be more accurate, my analogy would have to say segment 50, offset 41 to refer to room 541. This means that technically you could start a new segment every 10 rooms. Thus it would be possible to refer to room 541 also as segment 54, offset 01, or segment 52, offset 21, or segment 53, offset 11, etc. I hope this helps, memory is the most difficult aspect of the PC to fully understand. Thanks for your interest, and I hope you like the new upcoming 10th anniversary edition! The memory chapter has been significantly enhanced. 7. Should I install parity memory? Reader: I keep wondering if I should replace the non-parity SIMMs (4 x 16 x 32) with the (4 x 16 x 36) I have bought to see if this makes any difference. Computer Doctor: It's probably not worth replacing what you have, but make a pact with yourself that your NEXT system must have ECC. 8. Should I believe salespeople when they tell me the parity memory isn't necessary? Reader: All the computer stores in town tell me that the "new systems" don't need parity memory. I know that it is a newer memory technology, but some stores carry it and some don't. When I ask questions about it, no one can explain it to me. So, how can they tell me I don't need it if they can't explain it? I always thought parity memory was better/safer because at least one gets a warning if you get a parity error and you know something is "flaky." Is this true? Computer Doctor:They are blowing smoke about something for which they clearly have no knowledge. Don't believe anything a computer salesman tells you. That's my motto. Get the parity memory. Even better than parity (for Pentium and higher systems) is ECC, which uses the same parity memory but to a higher level, it will not only detect errors, but can correct them on the fly, greatly improving overall system reliability and integrity. Parity (or now ECC - Error Correcting Code for Pentium and beyond) memory is all I will use in my systems. 9. What does PNY mean in reference to SDRAM? Reader:Can you briefly describe what the new "PNY" designation means with regards to SDRAM? Computer Doctor: It means the modules in question were made by: PNY Technologies
299 Webro Rd
Parsippany, NJ 07054
Tel. 973-515-9700
Fax 973-560-5590 They are a fairly large manufacturer of SIMMs and DIMMs.
10. Can you explain re-mapping unusable Upper Memory into extended memory? Reader: In your book, you write about how otherwise unusable Upper Memory is made usable by re-mapping it into extended memory. I can't see how this produces more available memory if it takes extended memory out of use. I think I am missing something. Is it that it is given an address at what would be the beginning of the next (but nonexistent) memory chip? Computer Doctor: Actually you are re-mapping extended memory into upper. You don't have more total memory, in fact the whole procedure uses up some memory overhead to load the drivers and such so technically you are losing memory. What is happening though is that you are placing memory in an area where 16-bit (DOS based) drivers can use it. Only 32-bit drivers and software can load into the second megabyte and beyond. 11. Can EDO and FPM be mixed on the same system? Reader: On page 803 (of the 8th Edition) you state that EDO RAM can be used in a system designed for FPM SIMMs and vice versa, with no ill effects. Therefore, when I had an opportunity to purchase a 16MB EDO SIMM to replace my two 8MB FPM SIMMs ( one of which was static damaged. I did so. It works great. What you did not mention is whether or not the two types can be mixed? Computer Doctor: If your system will use EDO with no problem then they can also be mixed with no problem. Most systems will allow mixing bank by bank, however some may not allow mixing WITHIN a single bank. Remember on a 486 system without interleaved memory, a single 72-pin SIMM constitutes a single bank, while on a Pentium system two SIMMs make a single bank. 12. How do I identify DIMMs that are compatible with my motherboard? Reader: After installing an additional a 32 MB DIMM, I discovered that the computer wouldn't recognize the chip. Even just using new chip alone, it still doesn't work. Later, I learned that my Intel Tigereye motherboard only supports certain memory types (for example, it does support 2CLK). However, it does not support 4CLK SDRAM memory. Nobody can tell me the difference or how to identify between the two. Can you? Computer Doctor: These minor types of incompatibilities point out why it is important to purchase DIMMs only from reputable manufacturers with knowledge of the standards and the products such as Kingston, Micron (Crucial), Smart, Simple, Viking, etc. They would have asked you which motherboard the memory was going to be used in and then only shipped you DIMMs, which would have been compatible.
The problem is that the VX chipset was one of the first chipsets on the market to support SDRAM DIMMs at all, and as you now know, is lacking in several areas. I don't know what you paid for your 32M DIMM, but you should be aware that you can get a brand new Pentium motherboard with the (newer and better) 430TX chipset for about $70 that should support both of your DIMMs. In other words, you may be better off replacing your motherboard than your DIMM. The new board will also have a more modern BIOS, a higher performance IDE interface, and many other improvements over your existing board. The problem with your chipset (and board) is that there are a total of 4 clock signals available to SDRAM DIMMs, but your chipset only supports two of them. The additional clock signals are required by DIMMs which have more physical chips onboard. This effectively means that you can't use DIMMs with greater than 10 SDRAM chips on them. CK0 (pin 42), CK1 (pin 125), CK2 (pin 79) and CK3 (pin 163) are the four clock signals. CK0 is used in all SDRAM DIMM configurations. In general (with a few possible exceptions) CK1 is used in all DIMMs containing greater than five SDRAM chips, and CK2 - CK3 are used in configurations with greater than 10 SDRAM chips. All of the unused clocks are terminated with a capacitor to approximate a load of four to five SDRAM chips. For all clocks that drive less than four SDRAMs a padding capacitor is added such that the total clock net approximates a load of four to five SDRAMs. Note that Intel has created standards for SDRAM and SDRAM DIMM design for PCs. For more information on these standards, see: http://developer.intel.com/technology/memory/index.htm
13. Why won't OS/2 load after installing more memory? Reader: I ran into problem adding faster memory to a system when I tried to load OS/2 version 2.1. It refused to load. I had a 16 MB, 70 ns SIMM and added another 16 MB, 60 ns SIMM (my dealer did not have 70 ns on hand and gave me the faster SIMM for the same price). Windows NT Workstation version 3.51 loaded and worked fine, recognizing 32 MB, but OS/2 gave me some bad memory messages. I had to return the 60 ns SIMM to the dealer and get a 70 ns one, then OS/2 was satisfied. Computer Doctor: I've always said that OS/2 was the best memory test program I had ever seen. That is because I think it works the memory more than other programs. As far as your problem, there could have been problems due to differences in the memory refresh design (2K or 4K refresh) between the chips you had and the ones you added which affected this rather than the speed. Also the SIMM you had could have been bad or marginal. If the same type of memory had been used the speed should not have made any difference. 14. What is SGRAM?Reader: Lately, I've been hearing about SGRAM being used on some video cards for the last 2 or 3 months. I don't have any clue what it is and nobody I've talked to has known either. Can you explain it to me? Computer Doctor: The full name is Synchronous Graphics RAM. It is a type of SDRAM which is dual ported for video cards. Dual ported is so the video chipset and DAC (digital to analog converter) can both read the data from the chips at the same time. The synchronous part means that the memory runs at the true board clock speed (33MHz if it is a PCI board), and thus can transfer data in sync. with the system using less wait states. 15. What kind of memory retains information after the computer is powered off?Reader: Do you know of any memory that is programmable and still retains the info after its powered off (something like EPROM, EEPROM or CMOS). Computer Doctor: EEPROM and or Flash ROM does exactly that. I have a 20MB flash memory card which I use in my laptop PC for temporary working backup while on the road (I can backup up to 20MB of my current working files), and also in my digital camera. It stores data permanently without power, and yet works just like a hard disk, except faster! The 20MB PC-Cards (PCMCIA) are about $200 now I believe. You can get them in capacities up to 100MB or more! 16. I'm curious about the advantages/disadvantages of using ECC memory.Reader: A technician at a major memory vendor (Crucial.com) told me that I wouldn't need ECC memory unless I was running very data-critical applications, and I would also slow down my computer if I installed ECC memory. Did I get the straight scoop, or is ECC memory worthwhile?
Computer Doctor:Putting the chipset into ECC mode does slow down memory access by a very small (i.e. imperceptible) amount due to the time added for the ECC generation and checking. I still use ECC memory on all of my systems where it is an option. The small additional cost is worth the fewer hassles and less crashes. Everything I do on a computer is a "data critical application". After all, I don't play games: computing is my business. And, as memory densities and capacities increase, so does the possibility of soft (i.e. cosmic-ray induced) errors. That's why I continue to purchase and install ECC memory for my systems which support it (i.e. my laptop doesn't). I am into 'overkill' - being better safe than sorry. That's why I also install much larger power supplies than the minimum required (such as a 450 watt where a 250 watt would be adequate).
17. Virtual Channel Memory (VCC-133) - is it really faster and more energy efficient than PC-133?Reader: I recently bought an Asus A7V motherboard which supports either PC-133 or VC-133 SDRAM modules. The VC-133 SDRAM is 50% faster and 30% less power hungry, but I haven't heard very much about this Virtual Channel Memory. Is it really better?
Computer Doctor: VC (Virtual Channel) memory is a form of SDRAM developed by NEC (now Elpida Memory) in 1998 that incorporated high speed registers called channel buffers to allow a higher transfer rate than standard SDRAM. Unfortunately, this type of memory never really caught on, and is only supported by a few motherboard chipsets (none from Intel or AMD), and only one company largely makes all the VC memory (NEC). It has already been superceded by newer and faster memory technologies such as RDRAM or DDR SDRAM. Because it's rare and the fact that RDRAM and especially DDR have much greater performance and are supported by many more motherboards, I wouldn't recommend VC memory at this point.
18. I'm trying to upgrade my SIMM memory but can't get the PC to recognize the new chips, why not?Reader: I tried to upgrade my memory by installing a 64MB SIMM module; my PC already has two 32MB SIMMs. The PC did not detect the additional RAM. I was advised to remove the SIMMs altogether and install a 128MB DIMM. The PC still did not detect it. What am I doing wrong?
Computer Doctor:On Pentium and later systems using SIMMs, SIMMs need to be installed in matched pairs. DIMMs can be used one at a time, but most systems don't allow mixing SIMMs and DIMMs. Some of the early motherboards with DIMM sockets are very picky about the type of DIMMs you install, so even if you remove all the SIMMs, you probably don't have the correct type of DIMM for your system.
I recommend you visit http://www.crucial.com and use their on-line system to locate the proper memory for your specific system. All you need to do is input the system make and model, or if you know the motherboard make and model you can use that too.
Note that with most older Pentium systems, adding more than 64MB will dramatically slow the system down since memory past that point can't be cached. In most cases with a system as old as yours, I'd recommend you either leave only 64MB of RAM in the system or upgrade the motherboard, processor and memory all at the same time.
19. So many types of RAM, what's the best?Reader: AMD supports SDRAM and DDR SDRAM, while Intel currently supports SDRAM and RDRAM, and will soon be supporting DDR SDRAM. There is another RAM called SLDRAM which is also protocol-based (as is RDRAM) and is an open architecture. Its performance is as good as any DDR SDRAM and RDRAM. When will this RAM will come to market? Which RAM types are best?
Computer Doctor: Both RDRAM and DDR SDRAM are better than SDRAM (up to twice as fast). Currently RDRAM is 3 to 5 times more expensive than DDR SDRAM. That makes DDR SDRAM clearly the best value.
I believe DDR SDRAM will be the prevailing standard unless the price of RDRAM falls considerably. At least until QDR (Quad Data Rate) SDRAM debuts. QDR will be the likely successor to DDR in a couple years.
As for SLDRAM, if you check the SLDRAM website at http://www.sldram.com, you'll see they stopped issuing press releases after it was supposed to be released in 1998. Apparently this type of memory 'died' before it was ever born, and no motherboard chipsets support it either.
20. Can I add a DIMM chip in addtion to my SIMM chips on my Microstar International motherboard?Reader: I have a Microstar International motherboard MS-5145 ver 2.1 and its memory configuration includes 2 SIMM banks (each with 16 MB) and 2 DIMMS (currently empty). Can I add a 32 MB DIMM and leave the SIMMS thus giving me 64 MB or do I have to only use DIMMS or only SIMMS?
Computer Doctor:According to the documentation on the MSI site http://www.msi.com.tw/support/manual/oldmanual.htm, you can't use SIMMs and DIMMs together. If you do dispose of your SIMMs and switch to DIMMs you'll also have to reset the memory voltage jumpers J1 from 5V (SIMM voltage) to 3.3V (DIMM voltage). You do this by moving the two jumpers from 1-3 to 3-5 and from 2-4 to 4-6.
Note that virtually all boards with both SIMM and DIMM sockets can use only one or the other at a time. I recommend you purchase your memory from , they are the memory vendor I recommend the most. Note that your motherboard uses the Intel 430TX chipset which only supports caching up to 64MB of RAM. This means that if you install more than 64MB you will slow the system down dramatically.
Rather than throw away 32MB worth of SIMMs just so you could purchase a single 64MB DIMM (which will be somewhat of a waste of money as you'll only gain 32MB in the process), I would recommend trashing this board and instead getting a new Socket 370 or Socket A motherboard, Celeron or Duron processor, and 128MB of SDRAM or DDR DIMMs. You could upgrade to 700MHz and 128MB of RAM with a new board for a total of $300 or so (including the board, processor, and RAM). See http://www.tccomputers.com or http://www.aberdeeninc.com for more information.
21. What kind of DIMM should I look for to accomodate my Pentium Motherboard/133MHz CPU?Reader: I have a Pentium Motherboard with a Pentium 133MHz CPU (Not MMX) Intel i430VX PCI Chipset. The system reads PC100 64MB DIMM as 16MB and reads PC100 128MB DIMM as 32MB. As a result my 192MB of actual RAM is being read as a total of just 48MB. Can you recommend the kind of DIMMs that I should be looking for? This motherboard has 2 DIMM slots & 4 72 pin SIMM slots.
Computer Doctor:The 430VX chipset was the first chipset on the market that even supported SDRAM at all, and that support was problematic at best. Among other things it required DIMMs with a special clocking requirement, and couldn't use high capacity versions, which is why it's incorrectly reading your large DIMMs as the smaller DIMMs it was designed to use. See http://www.crucial.com; Crucial's web site should have the type you need and will know what works in that board.
Note that you cannot use SIMMs and DIMMs simultaneously (remove any SIMMs when you install the DIMMs), and I doubt that the 430VX chipset will handle 128MB DIMMs at all and may not work with even 64MB DIMMs.
Also note that the 430VX won't cache any memory past 64MB, which means if you install any more memory than 64MB, you will dramatically slow down your system because the cache will be partially disabled. Bottom line, I'd recommend you NOT upgrade the memory in that board, since it will be expensive and you'll get little benefit. With hardware that obsolete you should be thinking about either replacing the motherboard, processor and RAM as a unit, or possibly the entire system with something new. |
