Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
Paul, could you please explain to me the ##Mx## thing? I mean, for
instance, is a 64Mx8 mean there there is 8 chips of 64 Meg capacity? And
then, does that description skip showing the X1 or X2 banks. Why then
isn't memory described as, for instance 64Mx8x1 to designate a 512Meg stick
and 64Mx8x2 used to describe a 1Gig stick? Why do they omit that last
number?
Am I correct in understanding what you are saying?
Also, I know that DDR memory runs on both the rise *and* fall time of the
clock cycles, but how does DDR3 of the latest Video RAM work?
On Sat, 26 Mar 2005 12:54:58 -0500, Paul wrote:
> In article <1or91nmf92fl9$.i7si8vc1pwwi$.dlg@40tude.net>,
> signmeuptoo@earthlink.net wrote:
>
>> How do I know, by vendor description, if a RAM stick is single sided (chips
>> only on one side) vs. double sided?
>>
>> Are there advantages to getting single sided vs. double sided?
>>
>> TIA
>>
>> ~signmeuptoo
>
> In most cases, there is too little info available, to know what
> you are buying. Especially with the cheaper generic RAM.
>
> With Crucial, you take the Crucial part number, find a picture of
> the Crucial module on Newegg, get the Micron part number off the
> picture of the sticker, and then download a datasheet from Micron
> (they have a section devoted to their modules and to the chips
> they make). I have never seen a cross reference table, that
> converts a Crucial part number, into the Micron module used
> for that purpose.
>
> With Kingston, datasheet download links are available on the
> product description page.
>
> For Corsair, you can go to corsairmicro.com and download a
> datasheet from their product listings.
>
> Samsung also has datasheets:
>
http://www.samsung.com/Products/Semiconductor/common/product_list.aspx?family_cd=DRM030202
>
> Those are all the ones I know of, or have searched for.
>
> Crucial gives a hint, by putting "-8T" or "-16T" on the end
> of the part number, but not all adverts include that info.
>
> In terms of construction, a bank of RAM is any number of
> chips put side-by-side, to build a 64 bit wide array of memory.
> The most popular widths of memory chips are 8 bits and 16 bits.
> That means you could construct an array with four or eight
> chips. (It is irrelevant, but I believe I've seen 2,4,8,16, and
> 32 bit wide chips, but some of those are used for more obscure
> purposes. I have a x32 chip, for example, on a Xilinx development
> board.) When you find 8 chips on a module, it could be (8) (x8)
> chips or it could be two groups of (4) (x16) chips.
>
> So, what is relevant about banks of RAM ? In the case of FPM, EDO,
> SDRAM, DDR, DDR2, all the chips on the module load down the address
> bus. A module with 16 chips puts 16 loads on the address bus.
> A module with 8 chips puts 8 loads on the address bus. Each load
> has a certain input capacitance. A capacitor stores
> electrical charge, and the more you've got, the harder it is to
> wiggle the signal on the line up and down. What that means, is
> a DIMM with fewer chips on it, can be run at a higher speed if you
> are overclocking. So, what you really want, is a module with as
> few chips as possible, for the highest operating speed. But of
> course, a module with few chips on it, gives you less total memory.
> For overclockers, two single sided 256MB DIMMs, run in dual
> channel, is a typical overclocking config, but few people
> are really happy with only 512MB total RAM. If RAM chips of
> 32Mx16 were used, you could build that module with four chips.
>
> Registered memory gets around this, as a register (buffer) chip
> on the DIMM, forms an intermediate stopping point for the signals.
> The address bus from the motherboard only drives the register chip,
> then the register chip drives the 8 or 16 or 32 memory chips. The
> register chip increases the latency in getting to the module, so
> peformance drops due to that, but the advantage is, that many more
> DIMMs can be driven, before the address bus runs out of drive
> strength. That is why server boards can have larger arrays of
> DIMMs. But, as an overclocker, I doubt a registered DIMM would
> make a good candidate for overclocking, as the register chip
> has frequency limits to it that are likely tighter than
> a memory chip.
>
> At the densities most people are interested in, modules will
> have eight or sixteen chips. Now that larger chips are available,
> it is possible to find single bank eight chip 512MB modules,
> which cause less loading than a double bank sixteen chip 512MB
> module (that is the commodity configuration). Usually the
> price will be an indicator of what you are getting.
>
> For example, the first Crucial module here, uses 64Mx8 chips,
> and the second module uses 32Mx8 chips. Per 512MB worth of
> memory, the first module is 50% more expensive. If the first
> (1GB) module was half populated, with only eight chips, it
> would give 512MB of RAM, with half the electrical load on
> the address bus, of the second module.
>
> 1GB ‹ CT12864Z40B DDR PC3200 CL=3 NON-ECC UNBUFFERED $181.99
> 512MB ‹ CT6464Z40B DDR PC3200 CL=3 NON-ECC UNBUFFERED $ 59.99
>
> In order to buy and use 512MB single sided DIMMs, your motherboard
> manual has to claim support for 1GB modules. This has to do with
> support for the memory chip size, rather than the module itself.
> As the chips are the same 64Mx8 on a 512MB single sided and a 1GB
> double sided DIMM, the row and column address signals are the
> same.
>
> I hope that isn't too confusing. With all the rows, columns,
> banks, and ranks on DIMMs, it is hard to keep track of all
> the issues.
>
> Paul