athlon xp question

ShadowBlade

Diamond Member
Feb 11, 2005
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i am building a low-budget PC for my mom and was thinking of going with AXP
the only ones newegg still has around is the 333MHz FSB ones, does this mean the fastest ram i can use is PC2700 (aka DDR333)(ive never dealt with non-a64 systems)
 

sangyup81

Golden Member
Feb 22, 2005
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right, the mobo sets the RAM speed unless it's set on AUTO
the only time you won't be able to use PC3200 is when your mobo can't handle it but most socket A mobos can
 

Fern

Elite Member
Sep 30, 2003
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Originally posted by: ShadowBlade
but it will always run at PC2700, correct even if i get (i wouldnt do this) PC4200

You wanna keep the ram and CPU insynch. That is, running at the same FSB for best performance.

I'd prolly just get some PC3200 Corsair Value Select and run it at 166/333.

Fern
 

BitByBit

Senior member
Jan 2, 2005
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That XP with a 333FSB was designed to be used with PC2700 RAM, and can only utilise the bandwidth of a single PC2700 Module.
If you can get PC3200 to run at 400MHz in your board, there will only be a very slight performance boost as a result of the slight decrease in latency from the increased clock speed.
IMO, get some CAS2.5 PC2700.
 

Fern

Elite Member
Sep 30, 2003
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Originally posted by: BitByBit
That XP with a 333FSB was designed to be used with PC2700 RAM, and can only utilise the bandwidth of a single PC2700 Module.
If you can get PC3200 to run at 400MHz in your board, there will only be a very slight performance boost as a result of the slight decrease in latency from the increased clock speed.
IMO, get some CAS2.5 PC2700.

No performance boost in running ram at 200/400 with a cpu at 166/333 on the XP platform.

The reason I suggested PC3200 (200/400) is if it and PC2700 costs the same, I'd take the faster everytime. Running PC3200 at PC2700 speeds may allow you tighten its timings as it's already underclocked.

BTW: Since you're shopping for CPU's, why not consider a mobile XP?. They'll run @ FSB 200 even though stock is 133/266.
 

BitByBit

Senior member
Jan 2, 2005
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Originally posted by: Fern
No performance boost in running ram at 200/400 with a cpu at 166/333 on the XP platform.

Increasing a module's clock speed also serves to reduce its latencies in terms of ns.

 

Fern

Elite Member
Sep 30, 2003
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It's been pretty well shown that for this platform asynch operation has a detrimental effect on performance. All the benchies that were posted on this have faded away since the advent of the 64bit platform.

Now, I understand that the reverse is true for Intel platforms. So, the diff is attributable to the diff CPU architectures.

Fern
 

Pederv

Golden Member
May 13, 2000
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My 3Dmark2001 scores drop 700 points when I run my Barton 2800 @ 333 and the memory @ 400. So even though my memory is 3200 I run it as 2700 (Barton @ 333, memory @ 333).

Killed my motherboard with a bad X800XT AIW got a NF7-S2G, now I can't run my Barton @ 400.
 

BitByBit

Senior member
Jan 2, 2005
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I haven't seen any benchmarks that show a performance hit when increasing the memory clock while keeping the FSB constant.
Just because the memory's effective speed is the same as the FSB, doesn't mean they're in perfect phase, especially when you consider RAM timings and also the fact that DDR modules actually run at half the effective clock speed natively.

Now, I understand that the reverse is true for Intel platforms. So, the diff is attributable to the diff CPU architectures.


I seriously doubt that difference in CPU architecture could account for this, assuming it is true.
More likely it's the fact that the P4's FSB is quad-pumped, and is able to utilise much more bandwidth than the XP's double-pumped FSB.
Actually, taking the 333FSB XPs as an example; they were only able to utilise the bandwidth of a single PC2700 module (333MHz * 8 ~ 2700MB/s), so they were bandwidth saturated from the start.