compatibility of old sdram: pc133, 100, 66

[afeasfaerw23231233]

i think it is right to post this here: i find out there's an interesting phenomenon on old box [pII, pIII] -- if you insert different brand of SDRAM with the same speed, it is very likely the speed will drop. e.g. my pIII 933mhz box have 3 stick of ram: 2 x hynix PC133 128MB and 1 x NEC[?] PC133 128MB. but if you put them together they would run at PC100. if you put only two of them they would run at pc133. would it be even better if i just install 2 of them? the trade-off is losing 1/3 memory for 1/3 faster speed. i wonder if you guys encounter similar problem

[tnseditor]

I haven't had any problem with ram speeds with the older computers I have worked with. I am not an expert, but I would rather have more ram than faster. Especially today I think that more ram is better.

[koleoptero]

I've had issues with sdram in the past. I had 2x128mb and when I tried to install another one (pc133 too) they just wouldn't work.

In your case though I'd go with using them all. The drop in performance will be greater if ram fills up and the system starts swapping.

[BDNiner]

I have had problems in the past with old motherboards that have 3 memory slots. You have less performance with 3 sticks installed as opposed to 2.

[sp0nge]

Greater performance in what way? And how noticable is this? I have a box with this 3rd slot and I've been thinking about filling it. I'd like to know more about how much effect (negative or positive) this could have on the machine.

[futureproof]

I know with DDRII memory that if you use both channels the overall speed of the ram drops. I don't think many motherboards support all DIMM slots being used at full speed. Try a google search for more answers but I'm sure it's a common thing.

[Iam138]

Faster bandwidth does not always equal better performance. In your case the speed difference b/t PC100 and 133 is neglible (33Mhz obviously). So you gain 33MHz @ the expense of 128MB which in the case of your PIII you need all the RAM you can get as it will take load off the CPU as well as reducing the need for the system to resort to your swap which will definitely give you performance hit.

In short you will likely notice better performance by adding more MB but unlikely you'll see any difference b/t 100 & 133MHz.

[afeasfaerw23231233]

Faster bandwidth does not always equal better performance. In your case the speed difference b/t PC100 and 133 is neglible (33Mhz obviously). So you gain 33MHz @ the expense of 128MB which in the case of your PIII you need all the RAM you can get as it will take load off the CPU as well as reducing the need for the system to resort to your swap which will definitely give you performance hit.

In short you will likely notice better performance by adding more MB but unlikely you'll see any difference b/t 100 & 133MHz.

yes, i think so. so my mobo is now running 3 x 128MB PC133 at PC100 speed

I know with DDRII memory that if you use both channels the overall speed of the ram drops. I don't think many motherboards support all DIMM slots being used at full speed. Try a google search for more answers but I'm sure it's a common thing.

this box is using sdram so it doesn't support dual channel, speed should not drop even i fill up all 3 slots. i am sure if i use the same brand of ram [e.g. kingston pc133 128mb x 3] then i can run at pc133. however i only have mixed brands of ram stick in hand.

[Iam138]

yes, i think so. so my mobo is now running 3 x 128MB PC133 ad PC100 speed

this box is using sdram so it doesn't support dual channel, speed should not drop even i fill up all 3 slots. i am sure if i use the same brand of ram [e.g. kingston pc133 128mb x 3] then i can run at pc133. however i only have mixed brands of ram stick in hand.

Maybe,maybe not, some old boards will indeed reduce the bandwidth if all the slots are filled ( I had an old MSI socket A board that did the same thing). This is true even today with some boards utilizing DDR2 as mentioned by futureproof. Regardless it's always a better idea to run matched DIMMS if possible.

[ssam]

how can you tell what speed you ram is running at?