Recently, I upgraded my PC’s RAM to 1.5 GB (Previously, it had been 512 MB). Before upgrading, there had been one stick of 512 MB RAM (not two 256 MB ones). So, I bought another RAM stick, a 1GB one. When I had installed this RAM stick alongside my old RAM, I booted up the computer.
At boot-up, a black screen with a message appeared, saying:
‘The firmware has detected that the amount of memory in Channel A is unequal to the amount in Channel B. For maximum performance, make sure that the amount of memory in both channels in equal.
Press Enter to continue.’
I pressed Enter to boot up the OS. Anyway, the computer ran fine. It was noticeably faster than before, especially when multitasking. But the black message that I had seen on bootup still bugged me.
I just wanted to know: was it a good idea to let a 512 MB RAM stick be installed alongside a 1 GB stick? Or, to make the question simple: would it be in any way better if I removed the 512 MB RAM stick and left myself with one chip of 1GB RAM instead of two different ones? Since with 1.5 GB RAM, hardly 30% of RAM is used when I’m normally working, 1 GB RAM wouldn’t be so less that swap would have to be used; so I suppose performance would be more or less the same.
(Sorry if this question contains non-hardware comments, I just couldn’t find anywhere else to post it)
What you are saying is quite common. Many motherboards exhibit strict rules about memory. Usually when 2 memories are used they must be identical size and speed and must also match the specs for the MBO. Some MBO’s allow a single stick but this too must match with the specs required for the MBO. Combining different sizes is very bad as how can the system properly deside on the matched size of memory. Using different speeds can be disastrous as information from one bank will arrive at a different time than the other.
:\
Does that mean it would be better if I removed the 512MB stick? If my PC’s performance won’t suddenly reduce drastically if I do that, (which I expect it won’t 
) then that’s not a good choice. But I guess 1GB is also good enough for me.
BrownieCat wrote:
> At boot-up, a black screen with a message appeared, saying:
> ‘The firmware has detected that the amount of memory in Channel A is
> unequal to the amount in Channel B. For maximum performance, make sure
> that the amount of memory in both channels in equal.
> Press Enter to continue.’
Is it a recent motherboard? Most surely you are facing a dual-channel
configuration:
http://en.wikipedia.org/wiki/Dual-channel_architecture
“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.”
So unless you get some glitches (random system restarts or shutdowns) I will
keep that 512 MB module on.
Greetings,
–
Camaleón
Some mobos require for single channel operation for you to put these modules on specific banks. F.ex my ASUS mobo requires modules to be put on Bank B (which has two channels so I can place two modules) for single-channel mode only. Since you mix a Gig module with a 512MB one, you’ll be operating in single-channel only (double channel requires modules of identical sizes) so check the docs of your mobo where modules for single-channel only need to be placed
Also, what techwiz03 said that using different speeds will be “disastrous” is a lie. Memory controllers will automatically detect the speeds of modules and if they are not the same, will automatically clock all modules to the speed of the slowest module. F.ex you can mix DDR333 with DDR400 but the controller will downclock the DDR400 to DDR333 speed (200 MHz -> 166 MHz). On the other side, and note I’m only talking here about older DDR1 memory, is that all DDR1 chips can operate at higher speeds, i.e. DDR333 and even DDR266 can operate just fine at 200MHz (DDR400) as there’s absolutely no difference between a DDR266 chip and a DDR400 chip. The reason modules are sold with a DDR<speed> stickers on them is to tell at which speed that module is guaranteed to operate (ie, the factory has tested this module only at this speed and thus markets it only for this speed and can guarantee it’ll operate correctly at it).
Oops… I removed the 512 MB RAM stick before I read the new posts…
Anyway, I’m not noticing any difference between the performance of my PC with 1 GB RAM and with 1.5 GB RAM. Right now, as I’m typing this in Firefox (the only application running), only 24 % of my total 1GB RAM is being used, and that’s a pretty good sign. Since 1.5 GB RAM isn’t going to give me any benefit as compared to 1GB, I’ll stick with it. Besides, I don’t really need so much RAM; I upgraded because I experienced slowdowns when I began multitasking on 512MB.
Currently I’m happy with 1GB. My system’s become really snappy as compared to before. lol!
If your system is at some limit for ram usage or your motherboard is particularly picky then having identical modules can be helpful. Most people wouldn’t notice any speed difference from using mismatched modules. Having enough ram is much more useful than having matched modules.
All that said, most linux systems will run very well with 1GB of ram with not much improvement after that. I’ve noticed significant improvements with upgrades to 1GB of ram from 512mb or less.
A 1GHz P3 with 1GB of ram will have no trouble with opensuse 11.1. The same system would choke on Vista.
microchip8 wrote:
> Some mobos require for single channel operation for you to put these
> modules on specific banks. F.ex my ASUS mobo requires modules to be put
> on Bank B (which has two channels so I can place two modules) for
> single-channel mode only. Since you mix a Gig module with a 512MB one,
> you’ll be operating in single-channel only (double channel requires
> modules of identical sizes) so check the docs of your mobo where modules
> for single-channel only need to be placed
Does it not follow that having a single module implies single channel
operation in the initial configuration? That being the case, adding a
second module that forces single channel operation is a wash - you gain
performance via increased cache and reduced swapping - but you don’t
really “lose” anything by not using the dual channel, you just don’t
realize the potential gain hardware.
–
Will Honea
if you are using single channel memory now then adding a second module to your system will increase it’s performance, whether it is a different capacity or speed. I just pulled a pc 2100 128mb stick (one of two matched sticks that came with the machine) out of an old dell dimension 2400 this morning and added a pc3200 512mb stick in and its a huge difference. the pc3200 is down clocks to 266mhz, but it’s still a 512mb increase in memory.
No, it does not follow. This is a chipset limitation and is even mentioned in the manual. If you place a single module on Bank A and boot this mobo, it won’t fire up as it’ll think there’s no memory installed. If you place that module in Bank B (either channel 1 or 2) it’ll happily boot 
Excerpt from PC magazine archives 2007
The “problem” is simply that different computer motherboards can accept memory in different, but specific, combinations. Some examples:
* Some require that all memory sticks in the computer be identical. So if you have four slots, you can have 4x256meg, or 4x1gig, but you can't mix the 256meg and 1gig sticks.
* Some allow you to mix, but you must mix in pairs. Meaning you might be able to have 2x1gig and 2x256meg.
* Some require that if you mix, you must do so in a certain sequence. So you might be able to put 1gig in slot 1, and 256meg in slot 2, but not the other way around.
* Some single channel boards don't support memories of differing speeds but are quite OK with mixed sizes.
* Some dual channel boards don't care about speed and will simply degrade to the slowest but often this is done by limiting the variance of size per slot and or order of placement.
* Many require that if you mix (according to whatever other rules there might be), the memory sticks share certain other characteristics, such as speed or others.
As you can see it’s not a simple yes you can, or no you cannot. It really does depend on the machine you’re dealing with. Before making changes your first line should be to review the memory requirements from the manufacturer of the motherboard. Just because a certain combination of memory seems to work does not mean it will work over an extended period of time.
hope this helps
Rick
microchip8 wrote:
>
> Will Honea;2045704 Wrote:
>> microchip8 wrote:
>>
>> > Some mobos require for single channel operation for you to put these
>> > modules on specific banks. F.ex my ASUS mobo requires modules to be
>> put
>> > on Bank B (which has two channels so I can place two modules) for
>> > single-channel mode only. Since you mix a Gig module with a 512MB
>> one,
>> > you’ll be operating in single-channel only (double channel requires
>> > modules of identical sizes) so check the docs of your mobo where
>> modules
>> > for single-channel only need to be placed
>>
>> Does it not follow that having a single module implies single channel
>> operation in the initial configuration? That being the case, adding a
>> second module that forces single channel operation is a wash - you
>> gain
>> performance via increased cache and reduced swapping - but you don’t
>> really “lose” anything by not using the dual channel, you just don’t
>> realize the potential gain hardware.
>>
>> –
>> Will Honea
>
> No, it does not follow. This is a chipset limitation and is even
> mentioned in the manual. If you place a single module on Bank A and boot
> this mobo, it won’t fire up as it’ll think there’s no memory installed.
> If you place that module in Bank B (either channel 1 or 2) it’ll happily
> boot
AH! The old master/slave conundrum. Good to know as I have to replace a
couple of boards shortly and was unaware of this issue.
–
Will Honea
I don’t know what PC Magazine “knows” but I have yet to see a memory controller that will not downclock modules if one module runs at a lower speed than the others. Heck, even older mobos still using ancient SDRAM do that automatically, ie place a 66MHz and a 100MHz module on an old mobo and see for yourself and this isn’t very different for older first gen DDR mobos. I’ve worked with many many different mobos and chipsets from Intel, AMD, SiS, VIA, ALi with different types of memory (SDRAM, DDR1/2 SDRAM, RDRAM, etc) and all downclock. I certainly don’t know which are those “many” they speak of as I have not encountered one during the past 11 years
[QUOTE=Will Honea;2045887
>
> No, it does not follow. This is a chipset limitation and is even
> mentioned in the manual. If you place a single module on Bank A and boot
> this mobo, it won’t fire up as it’ll think there’s no memory installed.
> If you place that module in Bank B (either channel 1 or 2) it’ll happily
> boot ;)[/color]
AH! The old master/slave conundrum. Good to know as I have to replace a
couple of boards shortly and was unaware of this issue.
–
Will Honea[/QUOTE]
Note that this is only true for if you only use one module. The mobo is fine if you place modules of different speeds and sizes and it will downclock them to lowest one and put them all in single channel mode. But if you only have one module to use in combination with this mobo, you’ll have to place it in Bank B, either channel 1 or 2.
I have seen so many systems which contained mismatched modules and frankly, most of them have suffered premature failures. I guess if what you do on your machine holds no value, you can do what you want. I have experience spanning over 35 years including integrated design principals where pico-volts make or break the mold. The manufacturers take enormous care and strict type cast testing. I presume you do more than just grab a chipset and play assuming because you tried something and it worked it theoretically means you did things correctly.
As for PC magazine and many other PC publications, they all do various tests albeit some tests are questionable. They pride themselves on getting the answers straight from the horses mouth sort of speak.
Thusly, I stand by the time tested tradition of using authoritative published results from the manufacturers. If these results state do not mix different speeds, or sizes or adhere to specific placement I am sure they had good reason to state so.
I guess while were on the topic of what is right or wrong, The underlying overture heard all over the Linux community sites involves stability of systems and the abundance of problems faced with this or that piece of hardware. Yes the lack of manufacturers releasing controlling specs for their devices plays a major role.
As an engineer myself, I would like specs to be freely available but understand that there are reservations especially in regards to someone adversely using my product by not following the specs and thereby effecting the ROR (rate of returns). As consumers we want what we buy to work and there to be reasonable support if it
doesn’t.
So in conclusion, I just ask that people also check the specs as the developers more often than not took the time to lay out what is proper consideration for their product.
I don’t get it. How will downclocking a module will result in premature failure? I’m not talking about sizes here but speeds. I certainly have never seen or heard such things to happen. A module will be more than happy to run at lower speeds which can’t be said for higher speeds as one stresses it out - downclocking can even improve stability in a lot of cases (and this is not only valid for memory but for GPUs, CPUs, etc) and decreases heat dissipation, reduces power requirements and increases lifespan… Yes, what I do on my machines holds a lot of value to me and I’ve been mixing different speeds modules for many years now on different mobos and have yet to encounter “premature failures” just because certain modules get downclocked to match the speed of the others. If downclocking was such a bad idea and not recommended at all, certainly memory controllers will not have that feature and instead refuse to boot if modules of different speeds are installed