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high density vs. low density

 
 
mm
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      09-27-2007, 10:06 PM
Thank you all, especially Paul, for the very helpful answers in my
last thread.

I have an A7M266 mobo. Since my last post, I've been reading a lot
about memory, but I still don't get the difference between high and
low density memory, and which will work in my Asus mobo.


I have 512M** and I wanted to buy another 1G of memory,

I'm not going to do any overclocking (whatever that is. :-) )

P.P.S. If I get one more gig, should I move the 512 to the second
slot and put the 1 gig in the first slot? Or does it matter?

Thanks a lot.

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for some reason, remove NOPSAM :-)
 
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Paul
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      09-28-2007, 01:31 AM
mm wrote:
> Thank you all, especially Paul, for the very helpful answers in my
> last thread.
>
> I have an A7M266 mobo. Since my last post, I've been reading a lot
> about memory, but I still don't get the difference between high and
> low density memory, and which will work in my Asus mobo.
>
>
> I have 512M** and I wanted to buy another 1G of memory,
>
> I'm not going to do any overclocking (whatever that is. :-) )
>
> P.P.S. If I get one more gig, should I move the 512 to the second
> slot and put the 1 gig in the first slot? Or does it matter?
>
> Thanks a lot.
>
> If you are inclined to email me
> for some reason, remove NOPSAM :-)


A memory chip has row, columns, and internal banks, to make up the
memory array. The memory controller presents a row address and a
column address, during separate RAS and CAS cycles. The memory
address bus carries the information.

Say that your chipset has a 14 bit address bus. You decide to buy
a memory which needs 15 bits of address to carry the bigger of the
row or column address. If that happens, only half of the memory
will be visible.

A memory which causes that to happen, is referred to as a "high
density" memory. In previous cases, you might buy 16 chip DIMMs
which worked, or an 8 chip DIMM which didn't work. So since 8 chips
is "more dense" than 16 chips, people called it "high density".
But the chip count is not the only hint or indicator.

In the case of the 1GB DIMMs, you can make a DIMM with (16) 64Mx8
chips or with (16) 128Mx4 chips. The same number of chips are involved,
so it "looks like the same density". But the rows and columns needed
to address the "128M" part, is different than when addressing "64Mx8".
On some chipsets, this results in half the memory being detected.

If you want a guarantee it is going to work, buy from a
respected supplier with a warranty. I specifically mention Ebay
as a place to avoid, because of the danger of buying from someone
who won't help you when the memory is the wrong kind.

http://www.crucial.com/store/listpar...x?model=A7M266

This one looks fine. Install in whatever order works for you. Test
with memtest86+ from memtest.org, before booting into Windows with
the new memory in place.

http://www.crucial.com/store/mpartsp...0742B9A5CA7304

Paul
 
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mm
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      10-01-2007, 10:45 PM

Thanks again, Paul.

On Thu, 27 Sep 2007 21:31:51 -0400, Paul <(E-Mail Removed)> wrote:

>mm wrote:
>> Thank you all, especially Paul, for the very helpful answers in my
>> last thread.
>>
>> I have an A7M266 mobo. Since my last post, I've been reading a lot
>> about memory, but I still don't get the difference between high and
>> low density memory, and which will work in my Asus mobo.
>>
>>
>> I have 512M** and I wanted to buy another 1G of memory,
>>
>> I'm not going to do any overclocking (whatever that is. :-) )
>>
>> P.P.S. If I get one more gig, should I move the 512 to the second
>> slot and put the 1 gig in the first slot? Or does it matter?
>>
>> Thanks a lot.
>>
>> If you are inclined to email me
>> for some reason, remove NOPSAM :-)

>
>A memory chip has row, columns, and internal banks, to make up the
>memory array. The memory controller presents a row address and a
>column address, during separate RAS and CAS cycles. The memory
>address bus carries the information.
>
>Say that your chipset has a 14 bit address bus. You decide to buy
>a memory which needs 15 bits of address to carry the bigger of the
>row or column address. If that happens, only half of the memory
>will be visible.
>
>A memory which causes that to happen, is referred to as a "high
>density" memory. In previous cases, you might buy 16 chip DIMMs
>which worked, or an 8 chip DIMM which didn't work. So since 8 chips
>is "more dense" than 16 chips, people called it "high density".
>But the chip count is not the only hint or indicator.
>
>In the case of the 1GB DIMMs, you can make a DIMM with (16) 64Mx8
>chips or with (16) 128Mx4 chips. The same number of chips are involved,
>so it "looks like the same density". But the rows and columns needed
>to address the "128M" part, is different than when addressing "64Mx8".
>On some chipsets, this results in half the memory being detected.
>
>If you want a guarantee it is going to work, buy from a
>respected supplier with a warranty. I specifically mention Ebay
>as a place to avoid, because of the danger of buying from someone
>who won't help you when the memory is the wrong kind.
>
>http://www.crucial.com/store/listpar...x?model=A7M266
>
>This one looks fine. Install in whatever order works for you. Test
>with memtest86+ from memtest.org, before booting into Windows with
>the new memory in place.
>
>http://www.crucial.com/store/mpartsp...0742B9A5CA7304
>
> Paul



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