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  1. #1
    IT Consultant johcar's Avatar
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    Default New RAM not recognised

    HP Pavilion A1555A, running XP Media Centre, SP3.

    Original RAM: DDR PC2-4200U @ 1GB

    New RAM: DDR2 800Mhz PC6400 @ 1GB

    (The guy at PB Tech said that PC2-4200 and PC6400 were compatible - please confirm)

    Hmm - think I've just answered my own question.

    DDR and DDR2 don't mix, do they?

    Anyway the question was going to be about the fact that the increased memory does not display.

    Thanks in advance...

    I assume I'm going to need another stick of DDR2 and throw away the original DDR stick???? Or find another 1GB stick of DDR memory??

    It is impossible to defeat an ignorant man in argument. -William G. McAdoo, lawyer and politician (1863-1941)

  2. #2

    Default Re: New RAM not recognised

    Quote Originally Posted by johcar View Post
    DDR and DDR2 don't mix, do they?
    No. They are physically different so you should not have been able to put them both in the same motherboard unless the motherboard is one of the rare ones that has slots for both types.

  3. #3
    Computer Technician wainuitech's Avatar
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    Default Re: New RAM not recognised

    DDR and DDR2 are completely different RAM - the slots on the Mother Board are different as well.

    You cant install DDR2 RAM into DDR Slots and vise versa - they simply wont fit. You HAVE to get the correct RAM for your board.

    Some boards have the ability to take both types,they have both DDR & DDR2 slots, BUT you cant mix them- you either use DDR OR DDR2.

  4. #4
    IT Consultant johcar's Avatar
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    Default Re: New RAM not recognised

    Interesting - I am posting this after removing the original RAM stick and replacing with the new DDR2 (in the same slot).

    When held beside each other they look identical (except the original has chips on both sides of the stick) - the wee notch to ensure it goes in the right way around is in exactly the same spot, so perhaps I have DDR2 memory in fact (despite what the Crucial scan says).

    Which would bring me back to my original query - why is the extra stick not being recognised??

    It is impossible to defeat an ignorant man in argument. -William G. McAdoo, lawyer and politician (1863-1941)

  5. #5
    IT Consultant johcar's Avatar
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    Default Re: New RAM not recognised

    PS. with the new stick, the Computer Properties is showing 1GB RAM.

    It is impossible to defeat an ignorant man in argument. -William G. McAdoo, lawyer and politician (1863-1941)

  6. #6
    IT Consultant johcar's Avatar
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    Default Re: New RAM not recognised

    Quote Originally Posted by wainuitech View Post
    DDR and DDR2 are completely different RAM - the slots on the Mother Board are different as well.

    You cant install DDR2 RAM into DDR Slots and vise versa - they simply wont fit. You HAVE to get the correct RAM for your board.

    Some boards have the ability to take both types,they have both DDR & DDR2 slots, BUT you cant mix them- you either use DDR OR DDR2.
    Or is what you are saying that I have to get another 1GB stick of the same RAM I just bought and chuck out the old stick?

    It is impossible to defeat an ignorant man in argument. -William G. McAdoo, lawyer and politician (1863-1941)

  7. #7
    Computer Technician wainuitech's Avatar
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    Default Re: New RAM not recognised

    To answer Both Questions - Its IMPOSSIBLE for DDR to fit in DDR2 Slots and vise versa, the alignment slots are in different places, one reason for this is so you cant install the wrong sort, IF you did manage to get them in it would break the Board or at least damage it.

    I was going to take a Picture but Found this one instead as you can see the slots are in different locations - SO the original RAM you have is NOT DDR, its actually DDR2 - or vise versa. One way to tell is the gold contacts on DDR2 that run along the bottom are smaller and more of them than on DDR.


    Second question - why it wont work -

    Not all RAM works in HP /Compaq Computers - you cant just throw in any old name brand, some dont accept it, even if its the correct configuration (DDR or DDR2) - you dont have to get HP RAM - the ones that some times work are A-Data or Kingston or Corsair. Corsair works most of the time, but not always.

    Edited: just looked up the spec's for a HP Pavilion A1555A - it says its DDR2 Assuming this is the PC
    Last edited by wainuitech; 01-10-2008 at 04:27 PM.

  8. #8
    IT Consultant johcar's Avatar
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    Default Re: New RAM not recognised

    Quote Originally Posted by wainuitech View Post
    To answer Both Questions - Its IMPOSSIBLE for DDR to fit in DDR2 Slots and vise versa, the alignment slots are in different places, one reason for this is so you cant install the wrong sort, IF you did manage to get them in it would break the Board or at least damage it.

    I was going to take a Picture but Found this one instead as you can see the slots are in different locations - SO the original RAM you have is NOT DDR, its actually DDR2 - or vise versa. One way to tell is the gold contacts on DDR2 that run along the bottom are smaller and more of them than on DDR.


    Second question - why it wont work -

    Not all RAM works in HP /Compaq Computers - you cant just throw in any old name brand, some dont accept it, even if its the correct configuration (DDR or DDR2) - you dont have to get HP RAM - the ones that some times work are A-Data or Kingston or Corsair. Corsair works most of the time, but not always.

    Edited: just looked up the spec's for a HP Pavilion A1555A - it says its DDR2 Assuming this is the PC
    Yup, that's the beast alright!

    OK I can accept that I have DDR2 and that maybe the HP's can be a bit fussy.

    But what I can't understand is that the original Samsung 1GB stick works fine when installed by itself, as does the new Hynix Strontium 1GB stick, but when you put them both in, the machine only recognises one stick (who knows which one it's recognising - probably the stick in the primary slot)...

    It is impossible to defeat an ignorant man in argument. -William G. McAdoo, lawyer and politician (1863-1941)

  9. #9
    Computer Technician wainuitech's Avatar
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    Default Re: New RAM not recognised

    Quote Originally Posted by johcar View Post
    Yup, that's the beast alright!

    OK I can accept that I have DDR2 and that maybe the HP's can be a bit fussy.

    But what I can't understand is that the original Samsung 1GB stick works fine when installed by itself, as does the new Hynix Strontium 1GB stick, but when you put them both in, the machine only recognises one stick (who knows which one it's recognising - probably the stick in the primary slot)...
    yep - DDR2 by the looks of it.

    Regarding the Two Memory Sticks - just dont want to play together, yet they will run OK on their own - seen that happen a few times with HP/ Compaq - and some Dells as well.

  10. #10
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    Default Re: New RAM not recognised

    DDR2 800Mhz does not work on H P machines that max out at 667Mhz.

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