RAM question - One 256MB or two 128MB?

[Robor]

Looking to purchase 256MB of "Mushkin High Perf REV2 PC133 222" and can't decide on going with two 128MB sticks or a single 256MB. Price is not a factor as the difference is only a buck.

Question: Which is faster and/or which would be more stable? Is there any difference at all?

Thanks!

Rob

 

[Noriaki]

There might be a slight edge to the 2x128MB because it could have more open pages than the 1x256MB...but I seriously doubt you'd notice it...
Personally I'd get 1x256MB to save a RAM slot. But there would be at least a slight psychological edge for the 2x128MB
I think SDRAM is fast enough at page switching that the edge is really only theory, not practice, but like I said Psychological edge

 

[Robor]

Thanks. I've never read a big discussion on one or the other so I didn't think there was much difference either way. I order a 256MB for my Bro...

Rob

 

[paulerdos]

there shouldn't be any performance difference. the only factor here would be future expansion: with 1x256, you have more slots; with 2x128, you could later split them up (put 128 in another box, for example) for convenience. it's up to you to weigh these two options and pick the one that works for you.

 

[pillage2001]

Why waste two slots for 256 where you can have 512 with 2X256Mb??

 

[X14]

Actually there is a performance increase of about 5-10% when using 2 sticks v.s 1 stick. With 1 stick of 256mb ram you can only use 2-way interleaving. With 2 sticks of 128mb ram you can use 4-way interleaving.

Here are some benchmarks I ran using Sandra 2000.

interleaving diabled
ALU/Memory Bandwidth 405
FPU/Memory Bandwidth 457

2-way interleaving enabled
ALU/Memory Bandwidth 436
FPU/Memory Bandwidth 519

4-way interleaving enabled
ALU/Memory Bandwidth 454
FPU/Memory Bandwidth 567

 

[Linh]

x15,

how does this apply to games and apps?

 

[Shockwave]

x14, are you sure? I have 1 128 meg stick using 4 way interleave. I thought that @ 64 med, you could only use 2 way, anything above that you could use 4 way...But! On to the subject...What about reliability...If you not looking to increase above the 256 ram point for a long time, I would get 2 128, just in case one craps out....But then again, there is some braggin rights to 1 256 and if you decide to upgrade, you still have 2 free slots....

 

[X14]

Here's some 3DMark2000 benchmarks I just ran.

interleaving disabled
5983

2-way interleaving enabled
6025

4-way interleaving enabled
6046

The performance increase as measured by 3DMark2000 seem to be quite insignificant but nonetheless are quantifiable.

 

[X14]

Hey Shock, I think you're right. It looks like 1 stick above 64mb can use 4-way interleaving, I didn't know that. Maybe someone can run some benches using 1 stick at let us know. I'm pooped out and don't feel like opening up my puter to take out one stick re-run all the benches.

This is from Adrian's Rojak Pot which explains interleaving.

SDRAM Bank Interleave

Options : 2-Bank, 4-Bank, Disabled

This feature enables you to set the interleave mode of the SDRAM interface. Interleaving allows banks of SDRAM to alternate their refresh and access cycles. One bank will undergo its refresh cycle while another is being accessed. This improves performance of the SDRAM by masking its refresh time of each bank.

Each SDRAM DIMM consists of either 2 banks or 4 banks. 2-bank SDRAM DIMMs use 16Mbit SDRAM chips and are usually 32MB or less in size. 4-bank SDRAM DIMMs, on the other hand, usually use 64Mbit SDRAM chips though the SDRAM density may be up to 256Mbit per chip. All SDRAM DIMMs of at least 64MB in size or greater are 4-banked in nature.

If you are using a single 2-bank SDRAM DIMM, set this feature to 2-Bank. But if you have two 2-bank SDRAM DIMMs, you can use 4-Bank as well. If you are using 4-bank SDRAM DIMMs, you can set either 2-Bank or 4-Bank interleave.

Naturally, 4-bank interleave is better than 2-bank interleave so if possible, set it to 4-Bank. Use 2-Bank only if you are using a single 2-bank SDRAM DIMM. Note, however, that Award (now part of Phoenix Technologies) recommends that SDRAM bank interleaving be disabled if 16Mbit SDRAM DIMMs are used.

 

[Shockwave]

I know that with SiSoft Sandra in memory, using PC-133 @ 100 CAS 3 no interleave I get somewhere around a 290 / 300, in the reference systems it lists a Duron with 128 at like 367 / 400...When I jack up to 4 way interleave, pc 133, cas 2 FBS increase to around 150 mhx for the RAM, I get...cant rmemebr exactly....around 530 / 600 or 610. But I do know that with just pc-133 and 4 way i get something like 500 or 550 / 553 or so....So i think the biggest difference would be running @ pc-133 and CAS timing of 2....But the pc-133 is a givin right? Thats why we get it...

 

[X14]

Shock, the reason I thought 4-way didn't work with 1 stick is because that's what the Crucial tech support guy told me. I talked to them before I bought my memory and asked if I could run 4-way with just 1 stick and they told me that I couldn't, that's why I went with 2x128 instead of 1x256.

 

[peemo]

I thought it was better to get one stick if you were hoping to overclock at a low latency settings (CAS2). This is from the tech info on Mushkin's site:

Why can't I run CAS 2 with multiple memory modules installed?

Unregistered SDRAM limits the maximum frequency you can run SDRAM reliably with out having to introduce latencies, the reason is that more chips connected to the memory bus the greater the capacitance load.
Higher capacitance loads require more current to drive the signals to the valid voltage levels. So for the best memory bus performance, the less DIMMS the better (we've seen numerous examples of this, where a board will run stable with one DIMM, but lose stability once more DIMMs are added). Of course, less memory may result in better ?benchmark performance? for your memory subsystem, but if you don't have enough memory for your applications then there will be an even bigger performance hit on the performance of your whole system than just running your memory at CAS 3.
So if you need more and better memory performance it?s best to select a DIMM with the highest memory density supported by your motherboards chipset (check your motherboard manual). This results in less chips connected to the memory bus, therefore your memory bus will see less capacitance load.
Some of you may be thinking that Registered memory is a solution to this possible performance inhibitor, but it isn't. While Registered Memory will not significantly load the bus capacitatively because Registered Memory represents a smaller load on the memory bus, Registered Memory incurs an extra clock delay in your memory cycle. This makes CAS 2 registered memory perform like CAS 3 memory!. Registered memory should only be used if you need to install the maximum amount of memory possible. Many motherboard chipsets only allow a total of 384MB (or 128MB modules) of unregistered memory while allowing 1GB (256MB modules of registered memory, although each motherboard chipset varies as to the total and maximum module size it will allow.
There is a new solution to this problem that we are seeing on some newer motherboards. While most motherboards memory settings revolve around timing issues, a few motherboard are now offering extended BIOS settings, which allow users to change the voltage that feeds DIMM slots. This is feature is called VIO voltage, and if I were going to get a new motherboard I would make sure that it has the VIO voltage feature and that this feature allows you to tweak the voltage fed to the DIMM slots, not just the AGP/PCI bus and chipset voltages. Being able to tweak the voltage for the DIMM slots will allow you optimize the memory bus so you get it to run reliably depending on how loaded with DIMMS the memory bus is.