Wednesday, May 18, 2011

dual channel ram does not exist

Strictly speaking, there is, AFAIK, no such thing as dual channel ram. Or stated differently, AFAIK dual channel ram does not exist. Strictly speaking of course.

Lets use an analogy. I'll use RAID for hard drives. Although SLI and CrossfireX for video cards will also work. Lets keep it simple by limiting the examples to 2 drives.

  1. You have a PC with one hard drive. You want to upgrade to raid. Do you need to discard your old hard drive and buy a matched pair of RAID hard drives? No
  2. You have a RAID setup on another PC. You have another PC with a motherboard that does not support RAID. Can you reformat and transfer the pair of hard drives to the second PC? Yes
  3. You have PC with a motherboard that does not support RAID and it has a single hard drive which is obviously not in RAID. You have a second PC with no hard drives yet but the motherboard supports RAID. Can you reformat and transfer the pair of hard drives to the second PC?Yes
    Now lets  apply the analogy to ram. 

    1. You have a PC with one ram stick and the motherboard does support dual channel. You want to have dual channel ram. Do you need to discard your old ram and buy a boxed pair of so called dual channel ram sticks? No. See the wikipedia quote below for an explanation. 
    2. Can you use so called dual channel ram sticks in a motherboard that is single channel only? Yes. You can either use one or both of the ram sticks. Of course they will run in single channel mode.
    3. Can you use a single ram stick which is not part of a matched set of dual channel rams in a dual channel motherboard? Yes   

    This wiki article explains a lot


    Operation
    Dual-channel architecture requires a dual-channel-capable motherboard and two or more DDR, DDR2 SDRAM, or DDR3 SDRAM memory modules. The memory modules are installed into matching banks, which are usually color coded on the motherboard. These separate channels allow each memory module access to the memory controller, increasing throughput bandwidth. It is not required that identical modules be used, but this is often recommended for best dual-channel operation. It is possible to use a single-sided module of 512 MB[1] and a double-sided module of 512 MB in dual-channel configuration, but how fast and stable it is depends on the memory controller.
    If the motherboard has two pairs of differently colored DIMM sockets (the colors indicate which bank they belong to, bank 0 or bank 1), then one can place a matched pair of memory modules in bank 0, but a different-capacity pair of modules in bank 1, as long as they are of the same speed. Using this scheme, a pair of 1 GB memory modules in bank 0 and a pair of matched 512 MB modules in bank 1 would be acceptable for dual-channel operation.[2]
     Modules rated at different speeds can be run in dual-channel mode, although the motherboard will then run all memory modules at the speed of the slowest module. Some motherboards, however, have compatibility issues with certain brands or models of memory when attempting to use them in dual-channel mode. For this reason, it is generally advised to use identical pairs of memory modules, which is why most memory manufacturers now sell "kits" of matched-pair DIMMs. Several motherboard manufacturers only support configurations where a "matched pair" of modules are used. A matching pair needs to match in:
    • Capacity (e.g. 1024 MB). Certain Intel chipsets support different capacity chips in what they call Flex Mode: the capacity that can be matched is run in dual-channel, while the remainder runs in single-channel.
    • Speed (e.g. PC5300). If speed is not the same, the lower speed of the two modules will be used. Likewise, the higher latency of the two modules will be used.
    • Number of chips and sides (e.g. 2 sides with 4 chips on each side).
    • Matching size of rows and columns.
    Dual-channel architecture is a technology implemented on motherboards by the motherboard manufacturer and does not apply to memory modules. Theoretically any matched pair of memory modules may be used in either single- or dual-channel operation, provided the motherboard supports this architecture.
     Link


    AFAIK there is no special factory line that produces so called dual channel rams. There is only one factory line and it produces ram sticks. Those ram sticks are of course tested individually (in single channel mode of course) to see if they work. To make a so called pair of dual channel rams, the manufacturer merely gets 2 ram sticks from the same batch and tests them in dual channel mode. If they pass, they get placed in special packaging. This further testing and special packaging makes them a bit more expensive.

    The analogy can be extended to hard drives and crossfireX/SLI. They usually don't sell hard drives or video cards in matched pairs.

    Summary: so in the end, is there a benefit in buying a more expensive set of so called "dual channel" rams? Yes there is. You get the peace of mind knowing that its 100% guaranteed to work in dual channel mode and there will be no problems. But IMHO, if you just buy 2 sticks of the same brand and specs, your chances of it working are already near or over 99% anyway.

    The end

      replacable ink nozzles are better than fixed ink nozzles

      Inkjet printers work by firing ink through very small holes or nozzles. A small hole is easy to clog.

      There are 2 things that can clog a nozzle: lumps and hardened ink. Lumps can be either ink ingredients that did not dissolve properly in the manufacturing process or foreign contaminants.

      Hardened ink is usually caused by ink that stays in the nozzles when the printer is left unused for too long. How long? Its hard to say. I usually like to print something at least once a week, or at least power cycle the printer once a week. A printer when turned on usually squirts a small amount of ink into the waste pad to clean out the stale ink. That might be enough. The ink nozzles are covered by a cap whenever the printer is properly powered off to minimize exposure to the air which causes the solvent to evaporate and the ink to harden but it still happens. <source>

      The frequency of lumps and foreign contaminants is determined by the quality of the manufacturing process both for original inks and for refills. Almost all original inks are of high quality while for refill inks, the quality is more variable. Also, for refills, there is a theoretical chance of foreign contaminants like dust entering the system unless you use a refill system that is not exposed to air.

      If you do get a clogged nozzle, you can use your printer's cleaning utility. If that doesnt work you can get more aggressive like emptying the cartridge of ink, flushing it with cleaning fluid and filling it with cleaning fluid and running a clean cycle on the printer. If the nozzles are replacable you can try soaking the nozzles in cleaning fluid. There are several commercial cleaning fluids available but distilled water sometimes works.

      If however, cleaning doesnt work, then you have no choice. You have to replace the nozzles. If you have a fixed nozzle then you have to replace the printer. If you have replacable (also known as disposable) nozzles, then you can merely buy a new cartridge. This is the big advantage of replacable nozzles.

      wiki article on nozzles

      So yes, its possible that by chance, your nozzles wont clog. However ...


      If it doesnt, then you're ok. But if you are not lucky, then having replacable nozzles is an insurance policy. So the bottom line is :
      All nozzles will probably eventually clog so the best policy is to have replaceable nozzles.

      note: that to be fair, I did not mention any printer brand. My own personal printer is one of those major brands which favors replacable ink heads.

      the end

      Sunday, May 15, 2011

      verifying smart money on paypal - new for may 2011

      As of may 2011, the procedure has changed a bit. Read the notes at the end of the post

      I'm doing a step by step guide on how to link your smart money card to paypal and how to verify a smart money card on paypal. I assume you already have a paypal account and you have no credit cards linked to paypal yet.


      • If you use a prepaid smart cellphone, make sure your smart cellphone has enough load for several messages. PhP 10-20 should be enough
      • Make sure your smart money account has at least 100 pesos
      • Log into pay pal
      • Go to the My Account tab
      • Under my account, you should see: Overview, Add Funds, Withdraw, History, Resolution Center and Profile. Go to Profile
      • Select add/edit credit card
      • Note: I do not know if the name listed should be the same as the one on the credit card
      • Select mastercard
      • Type the card number. Do not type in any spaces or dashes, just the 16 digit number
      • type in the expiration date
      • type in the card verification number, the last 3 digits on the back of the card
      • check the billing address
      • Get your cellphone and go to the simcard menu. Select smart money then internet txns then unlock then choose the name of the smart money card then press OK to answer the question " unlock for internet?"
      • enter the w-PIN on the cellphone
      • You will get 2 text messages. They both come from Smart money and the first one says " 1/2 ". The second one says " 2/2 Unlocking your account signifies that u agree to the SmartMoney Terms & Conditions for internet purchase. For details please go to www.smart.com.ph/money "
      • Once you get both text messages, go back to your web browser and press the Add Card button
      • You will get a text message saying The php 43.xx may change depending on the exchange rate.
      • Paypal should display "You have successfully added a credit card. Please note that this credit card is now your primary card. For more information on your primary card, please refer to your Profile."
      • The 43.xx peso charge AFAIK will no be refunded
      That should be it.

      As of may 2011, paypal and/or smart changed something. It used to be there was no 43.xx charge. Adding a card was a free act. After adding a card you would need to verify your credit card in a separate step. Now, the 2 steps of adding and verifying a card are condensed into one step. How do I know? I tested it!!  Before the changes, around march 2011, I replaced my card due to physical damage. Since its a new card with a new number I had to ADD it to paypal and VERIFY it, using the old procedure (see below) and I was able to . However for testing purposes I removed the card and tried to add and verify it again. I was surprised when my card was charged 4x.xx pesos and there was no verify link visible. Thats what led me to write this blog entry.

      Also of note, you previously needed to enter a 4 digit code which you would get via text. That step is not present anymore.

      There are rumors that the amount you can buy with paypal is limited if you do not verify. However since I have been able to buy stuff online (albeit low value stuff) and I cannot find any link or way to verify my card, I'm assuming that this rumor is not true or was true until the change.





      For records purposes, I am repeating the old procedure which of course you cannot do anymore:
      After adding your card, you would verify it. This involves  a refundable 100 peso charge. You should see an option to verify the card. After the 100 pesos is charged, paypal will ask you to enter a 4 digit code. For a credit card, it should be in your credit card bill. For smart money, you can find the code in the bill you receive via text message. It should arrive in a few minutes.


      The end

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