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  Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU? 
 
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ZR RIFLE Dec 10, 2003, 12:54pm EST Report Abuse
Have a question: Just slapped together a new Asus A7N8X motherboard with a new Athlon 2500+ (1.83 Ghz) CPU that has a bus speed of 333 MHz. I'm using the old PC2100 DDR memory (1 Gig) from my old system to save a few bucks. My question is, is using that old 266 MHz RAM bottlenecking or slowing down the processor capabilities? I know a similar issue was addressed in another thread, but it was concerning an opposite scenario (faster RAM vs slower CPU bus speed). Will upgrading to PC2700 DDR make much of a difference?

Thanks - RN.


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Moody Woody Dec 10, 2003, 01:23pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
PC2100 is meant to be run at 266Mhz, so either you will be overclocking the RAM up to 333Mhz (not sure this will be possible with your motherboard, even when your cooling proves sufficient), or effectively underclock the CPU, if you motherboard supplies you with enough multiplier-options. Obviously, both options have 'some' disadvantages.

AMD 955
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ZR RIFLE Dec 11, 2003, 08:04am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Thanks -

Do you or anyone else know if upgrading to PC2700 DDR will be worth it? I'm thinking of just going to 512Mb at this time, compared to my 1 Gig of PC2100 I'm currently using.


Omniscient Dec 11, 2003, 08:31am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
First of all to Woody - no dis-respect but what u said was incorrect to my knowledge.

The Mobo uses a ratio to control the FSB frequency to RAM frequency. The old SDRAM used to use common ones of 3:4, 1:1, and 4:3.

Here's on old example to illustrate.

FSB = 100
Ratio = 3:4
RAM Speed = (100/3)*4 = 133.33Mhz

Using memory that operates at a lower frequency to your FSB will NOT cause a bottleneck. Of course upgrading to faster ram will mean better system performance overall. But slower RAM will not affect the speed of your FSB.

The mobo will according to CMOS settings use the respective ratio. I suggest setting your RAM frequency in the CMOS settings to SPD (Serial Presence Detect) most DDR Chips support SPD which tells the BIOS the optimum frequency.

The A7N8X-DLX (same board I currently own) supports SPD, it also supports manual selection of both the FSB and RAM frequency.
So got to Advanced Chip configuration in CMOS and set the RAM frequency to what you desire. (remember to times it by two which is the FSB multiplier)

For your PC2100 you want to either select SPD or 133Mhz for the RAM frequency.

Jason Maxfield Dec 11, 2003, 08:45am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
if you are gonna up your RAM to PC2700, might as well get yourself 2 sticks of Corsair XMS, to make it really worth your while! Your mobo supports dual channel, so you should get 2 256 sticks, and your system will blaze, not only because of the RAM being faster, but the XMS line runs 2.0 cas latency, which makes it even faster, and with dual channel, you can see upto a 50% improvement over using one stick alone! it will kill your PC2100 data transfer times!

Jason

Moody Woody Dec 11, 2003, 11:50am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
AJ, you're RIGHT. I should have remembered that from one of my old mobos, an MSI I thought it was. And even then, my current A7NX-X mobo may not have the exact options you mentioned, a quick glance in the setup made me clear it has a whole range of options to get the CPU on speed! (This reminds me not to reply when I should be in bed.....) Thank you for not flaming!

AMD 955
Gigabyte 790FX UD4
WD 500 + 2x1TB Raid
ATI 5770
Win7 SP1
+
Atari 800XL 256Kb + BlackBox + 20Mb etc etc

ROY G Dec 11, 2003, 12:14pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Simple answer : NO

ZR RIFLE Dec 11, 2003, 05:20pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Thanks for the input, guys, it's been immensely helpful. And Jason, I've decided to take your advice - I'm gonna go ahead and dish out a few bucks ($120 to be exact) and by a twin-pack of Corsair XMS PC3200 sticks (512Mb). They look like a good investment, and they were actually cheaper than the PC2700 modules.

Guess I'll just stick the old PC2100 memory in my old MSI board and build it for the wife or something. :)

deadkenny Dec 11, 2003, 06:50pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
I guess it depends how you define 'bottleneck'. I would say, YES, to some extent it will limit performance. Or at least, I would say on a single memory channel m/b it would. However, with dual channel DDR there's usually more memory bandwidth than the processor can effectively utilize (in other words the FSB is the bottleneck). So, if you're running dual channel PC2100, then it might not be bottlenecking the system. Async may be inherently less efficient, but it's an interesting offsetting situation in this case. How about you bench mark the memory and tell us how it compares to dual channel PC2700 in various reviews. In any case, I don't believe it's worth while replacing 1GB of PC2100.

Outlaw 77 Dec 11, 2003, 07:35pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
No, but your memory will be overclocked right out of the box.

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ZR RIFLE Dec 12, 2003, 11:32am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
So you don't think it's worth upgrading from 1 GHz of DDR266? I already placed an order from Newegg for the DDR400 (512Mb), so guess I'm stuck. Couldn't hurt anyway, and I'm eager to try out the "twin" sticks with the dual-memory channels. I'll see how it compares to the 1 GHz of PC2100 ram.

Funny, I had to reorder like 3 times, until I finally got the exact item right (Corsair TWINX512-3200LL). There's so many friggin' types/models of PC3200 Corsair RAM of 512 Mb, even in the twin sets - gets quite confusing.

Jason Maxfield Dec 14, 2003, 11:42am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Rich,

Let me know how that turns out, as I'm running a single stick of 512 PC2700 right now, that get's data read rates of 2300 mb/s using Aida32's memory benchmark.

Jason

ZR RIFLE Dec 15, 2003, 11:52pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Well I installed it and with used the Aida32 benchmark, I'm getting a stock reading of 2477 Mb/s, write speed at 902 Mb/s. Is that good? I'm not overclocking anything. I have to say I sympathize with all these others who have boot problems concerning the memory modules. I had to reinstall the RAM about 10-15 times until it finally booted normal. Something about the A7N8X modules - very finicky. Resetting CMOS and battery doesn't seem to help. Just trial and error I guess....sheesh.

But I have to say there is quite a difference, at least to me, even over 1 GHz of DDR266 ram (one 512 Mb stick in the single module and two 256 Mb sticks in the dual-channel modules). This Corsair RAM rocks.

Any suggestions on getting the most out of this memory would be appreciated - I'm pretty much a novice at this stuff.

ZR RIFLE Dec 16, 2003, 12:03am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Well I just ran another test and now I'm getting a reading of 2504 Mb/s.

ROY G Dec 16, 2003, 12:22am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
512ddr is plenty for just about any application.AJ gave you some good info. SPD is usually the most efficient setting to use ,let`s face it the PC knows what is best to use most of the time. But that 3to4 setting is right. If you have good ram it will be ok or maybe I should say TRUE ram ,you have to watch buying ram .A lot of the time they will sell you say 333mhz or 2700 ram and it is 2100 OC`d to 2700. So when you buy ram be sure you ask or be sure to order ram that say`s TRUE ram .Then there is space to OC. Good luck

ZR RIFLE Dec 17, 2003, 01:27pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Well now the system appears to keep rebooting by itself every now and then. I've been doing alot of research, and may downgrade to PC2700, as alot of folks are saying if my CPU speed (333MHz) and my RAM speed (400MHz) don't corrolate, then I'll end up with a pretty unstable system - especailly with this A7N8X mobo. I don't plan to do any OC'ing right now, and want something stable. I was originally going to go with the PC2700 anyway, so maybe I shoulda stuck to that decison.

Omniscient Dec 19, 2003, 01:51am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Rich, I'm running a Thoroughbred 2600+ with a 333FSB with DDR 400 RAM on the A7N8X Mobo and the motherboard hasn't given me a hard time at all.
There should be no practical reason why the machine reboots itself at different frequency levels.

You said you don't want to overclock, but have you checked your temp as it sits now?

If you'd like to test the different frequencies theory, set the system settings to user defined in advanced chip configurations. Set your FSB then at 200MHz, change your clock multiple to 10 and set your RAM frequency at 100% and the RAM timings to Optimal. Now your RAM and CPU are running at the same frequency if the machine doesn't reboot then u got me stumped except to say upgrade to BIOS Rev 1007.

If it does reboot then I'd start fiddling with RAM and stuff until it stopped rebooting
For instance my 400 RAM doesn't mind booting at a speed of 210 (resultant 420) but if I set the frequency to say 191 (382) then the RAM bitches like hell and hangs my machine, however if i underclock it to different levels it works. That justs raises an eyebrow on me as being weird. But the point - tweak and fiddle and faff until you get a nice working pc if you can't achieve it get another PC :>

ZR RIFLE Dec 20, 2003, 01:51pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Thanks AJ -

Actually I already swapped the DDR400 for the DDR333. Wished I saw your post earlier... :)

However, and this is strange, the memory readings I'm getting off this PC2700 (dual setup) are actually faster than when I was using the PC3200....! I'm getting readings between 2550 and 2560 Mb/s, and memory write is 950 Mb/s. This is stock settings, no OC'ing. Funny though, I was getting random reboots with this DDR333 as well, and tried upping the Vcore CPU setting a couple notches in the BIOS.

I do have the v2.0 of the A7N8X mobo, with the 1.007 BIOS update, so I don't know why it's been happening. But taking out and reseating the RAM seems to take care of it, and it will boot up. Weird.....

But I will try your some of your settings (tuned to the DDR333 that is), and see if it runs more stable. But upping the voltage of the CPU seems to have helped a lot.

ROY G Dec 20, 2003, 02:49pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
You said that you had 2x256ddr corsair 3200 sticks and 1 512ddr stick !! What was the 512 stick ? was it 3200 ddr also . And to be truthful you should never run 1 single stick of anything ,with dual channel memory. If you take the 512ddr?? out you will get better results.

ZR RIFLE Dec 20, 2003, 07:56pm EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
Roy -

Actually the single 512 stick is PC2100 leftover from the old system I had. I was running that plus two 256Mb sticks, making a total of 1 Gig. I was using the single leftover 512Mb stick in the meantime until the new shipment of the twin Corsairs arrived, which took only 2 days. When RAM prices go down, I will probably buy a 512Mb stick of PC2700 and combine that with the twin 256Mb sticks I have now. I just gotta make sure I insert it in the right slot, right?

Rodger Hylton Dec 23, 2003, 06:46am EST Report Abuse
>> Re: Will using PC2100 (266MHz) DDR ram slow down a 333 MHz bus speed CPU?
I'm looking to upgrade from a single stick of 512 PC2100 as well. I have a MSI KT6 Delta-LSR, XP 2500+ Barton @ 2.04. Does anyone know if this board supports Dual Channel Mode for memory? If so do I just pop two 256 PC 3200s in or do I need to change things in the BIOs? Thank for any help,


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