Synchronization of RAM and CPU

DriveEuro · Dec 4, 2002, 10:28 PM

So I'm gonna build a new computer for Christmas. I'm trying to pick out all of the components that I want. I see the Athlon XP 2600 333. So what are the benefits of synchronizing the CPU and RAM? I don't think I can really afford that processor, so I may just go with a Athlon XP 2200 or 2100. I am definetly getting a MOBO with a 333 chipset for my 333mhz RAM.

What I'm trying to see is if I get the 2200 or 2100 with 333 RAM will the RAM run slower than 333? What is the point of running the CPU and RAM at the same speed? I know, better performance. But what will happen with a 2200 and 333 RAM?

I'm kinda puzzled by all of this.

Vingen · Dec 7, 2002, 01:35 AM

dont buy those kt400 mobo wait for the kt400A then, kt400 mobo have trubble with higher than 202 fsb

Vampyromaniac · Dec 7, 2002, 10:15 AM

OK here's how it goes as fas as I understand, (if I'm wrong, someone will correct me):

Your RAM is 333MHz (PC2700), so the memory bus can run at 333MHz

If you get the xp2100 or xp2200, your FSB will be 266MHz

If you run the RAM at 333, and the FSB is 266, the FSB will be a bottleneck, and only allow 2100 MB/s of bandwidth from you CPU to the RAM (not the 2700 that the RAM can handle)

If you had the xp2600 333 version, then you'd have a 333MHz FSB, and get the full 2700 MB/s bandwidth from CPU to RAM.

Now, as far as I know, running RAM syncronously with FSB is a little faster.
So what you could do is: set your RAM at 266MHz (so it is synchronous,) and since your RAM is now running slower than it is rated, you can probably set aggressive memory timings (CAS, RAS, precharge, etc, whatever) and get some performance boost.

. . . I think

bottom line: when you have a CPU with a 266MHz FSB, having RAM at 333, 400, anything faster than 266 . . . your memory bandwitdh will always be limited by the FSB's 2100 MB/s of bandwidth.
Sure, DDR400 RAM will have 3200 MB/s of bandwidth from the RAM to the memory controller (in the Northbridge of the chipset), but from there to the CPU, it's limited to 2100 MB/second.

DriveEuro · Dec 7, 2002, 05:31 PM

Gotcha. That's all I needed... Thanks.

bocybo · Dec 19, 2002, 02:23 PM

Actually, with a true 333FSB motherboard such as the Nforce2, you can have a 333MHZ memory bus AND 333MHz CPU bus. The new athlons(2600 and up) are all capable of running a syncronized 333MHz bus.

Zarathustra · Dec 19, 2002, 04:50 PM

Vamp is correct. The AMD system bus isn't wide enough to warrant running the memory at a faster speed than the FSB. Intel is different though, it has enough bandwidth to benefit from faster memory. So the moral of the story is to run AMD synced Intel asynced

Vampyromaniac · Dec 19, 2002, 10:49 PM

Heh, and I just learned about this stuff recently

and bocybo, I did say that

bocybo · Dec 20, 2002, 04:18 PM

Sorry didnt see it at first. But you still have to make sure to get a motherboard that will support the 333MHz FSB. Some will some wont. I would reccomend the Asus A7N8X.

Matth · Dec 20, 2002, 08:41 PM

If you have a "Throughbred unlock" BIOS (no idea how they do that), then maybe you could lower the multipler, and run a slower version at 333 FSB, and lower the multipler to aviod a 25% overclock unless it really can take it

With an AGP 8x card, running memory async at 333, FSB 266 might be worthwhile, for an increase in RAM-AGP throughput if AGP textures are ever used.

schmegma · Dec 20, 2002, 08:54 PM

Maybe the theory of it all says one thing, but I can attest to the 4:5 ratioing to get 333 RAM bus on a 266 FSB processor does increase performance.

I have a 2100+ locked, running 266(133) with 333 running 333 and it does increase over running the DDR at 266.

Granted, yes I agree I would be better off running a lower multiplier and getting the 333 FSB and then dropping to the 1:1 mem:cpu ratio and having sync operation. All I am saying is there are gains to be had running 333 DDR bus in a 266 FSB system, even if the XP shouldn't benefit from the additional bandwidth in theory.

I can post Sanda info later once I get home if folks want it.

Matth · Dec 20, 2002, 11:11 PM

In some cases, you NEED to clock the ram faster.....

DDR-sync transfers as fast as the FSB can handle ONCE IT STARTS, but the setup time of DDR is ridiculous!

So unless you can use "aggressive" timings at 266 sync, and have to back out of them at 333 async, you may be gaining from faster setup cycles.

I also read somewhere that KT333 (and KT400) handles async RAM/FSB exceptionally well, while the nForce 2 recommends sync mode

Dec 4, 2002, 10:28 PM	#1
DriveEuro HardwareHeaven Extreme Member Join Date: Jul 2002 Location: Gurnee Illinois Posts: 4,677 Rep Power: 0	Synchronization of RAM and CPU So I'm gonna build a new computer for Christmas. I'm trying to pick out all of the components that I want. I see the Athlon XP 2600 333. So what are the benefits of synchronizing the CPU and RAM? I don't think I can really afford that processor, so I may just go with a Athlon XP 2200 or 2100. I am definetly getting a MOBO with a 333 chipset for my 333mhz RAM. What I'm trying to see is if I get the 2200 or 2100 with 333 RAM will the RAM run slower than 333? What is the point of running the CPU and RAM at the same speed? I know, better performance. But what will happen with a 2200 and 333 RAM? I'm kinda puzzled by all of this. __________________ [color=orange]ASUS P4P800 Deluxe [color=black]-[/color] 2.4C --> 3300mhz [color=black]-[/color] Mushkin PC3200 at 220 5-2-2-2 (cpu limited) [color=black]-[/color] BBAti 9800Pro at 430/375 [/color] [color=black]3[/color][color=gray]D[/color]M[color=black]a[/color][color=gray]r[/color]k[color=yellow]01[/color] [color=black]3[/color][color=gray]D[/color]M[color=black]a[/color][color=gray]r[/color]k[color=yellow]03[/color] 16001200 12801024

Dec 7, 2002, 01:35 AM	#2
Vingen DriverHeaven Newbie Join Date: Dec 2002 Location: Sweden Posts: 13 Rep Power: 0	dont buy those kt400 mobo wait for the kt400A then, kt400 mobo have trubble with higher than 202 fsb __________________ [color=blue]16227 3dmark[/color]....

Dec 7, 2002, 10:15 AM	#3
Vampyromaniac confutatis maledictis Join Date: May 2002 Location: somewhere dark Posts: 5,974 Rep Power: 77 System Specs	OK here's how it goes as fas as I understand, (if I'm wrong, someone will correct me): Your RAM is 333MHz (PC2700), so the memory bus can run at 333MHz If you get the xp2100 or xp2200, your FSB will be 266MHz If you run the RAM at 333, and the FSB is 266, the FSB will be a bottleneck, and only allow 2100 MB/s of bandwidth from you CPU to the RAM (not the 2700 that the RAM can handle) If you had the xp2600 333 version, then you'd have a 333MHz FSB, and get the full 2700 MB/s bandwidth from CPU to RAM. Now, as far as I know, running RAM syncronously with FSB is a little faster. So what you could do is: set your RAM at 266MHz (so it is synchronous,) and since your RAM is now running slower than it is rated, you can probably set aggressive memory timings (CAS, RAS, precharge, etc, whatever) and get some performance boost. . . . I think bottom line: when you have a CPU with a 266MHz FSB, having RAM at 333, 400, anything faster than 266 . . . your memory bandwitdh will always be limited by the FSB's 2100 MB/s of bandwidth. Sure, DDR400 RAM will have 3200 MB/s of bandwidth from the RAM to the memory controller (in the Northbridge of the chipset), but from there to the CPU, it's limited to 2100 MB/second. __________________ *Digitalis 3.3* Athlon 64 3000 // ASUS K8V SE Deluxe // 1024MB PC3200 (2-2-2-10 1T) ATI All-In-Wonder 9700 Pro // 20" Dell 2005FPW (DVI) M-Audio Revo 7.1 + Philips Acoustic Edge // Klipsch ProMedia 2.1 320/16 Western Digital WD3200KS + 120/8 Seagate 7200.7 NEC ND-3550A 16x DVD±RW + Lite-On 52x24x CD-RW Antec Sonata case // 480W Antec TruePower personal bests \|\| Aq'3: 46796 \| 3D'01: 20461 \| 3D'03: 6336 \| 3D'05: 2677 \| PC'04: 4605 \| PC'02: 7691,9092,1250

Dec 7, 2002, 05:31 PM	Thread Starter #4
DriveEuro HardwareHeaven Extreme Member Join Date: Jul 2002 Location: Gurnee Illinois Posts: 4,677 Rep Power: 0	Gotcha. That's all I needed... Thanks. __________________ [color=orange]ASUS P4P800 Deluxe [color=black]-[/color] 2.4C --> 3300mhz [color=black]-[/color] Mushkin PC3200 at 220 5-2-2-2 (cpu limited) [color=black]-[/color] BBAti 9800Pro at 430/375 [/color] [color=black]3[/color][color=gray]D[/color]M[color=black]a[/color][color=gray]r[/color]k[color=yellow]01[/color] [color=black]3[/color][color=gray]D[/color]M[color=black]a[/color][color=gray]r[/color]k[color=yellow]03[/color] 16001200 12801024

Dec 19, 2002, 10:49 PM	#7
Vampyromaniac confutatis maledictis Join Date: May 2002 Location: somewhere dark Posts: 5,974 Rep Power: 77 System Specs	Yay Heh, and I just learned about this stuff recently and bocybo, I did say that __________________ *Digitalis 3.3* Athlon 64 3000 // ASUS K8V SE Deluxe // 1024MB PC3200 (2-2-2-10 1T) ATI All-In-Wonder 9700 Pro // 20" Dell 2005FPW (DVI) M-Audio Revo 7.1 + Philips Acoustic Edge // Klipsch ProMedia 2.1 320/16 Western Digital WD3200KS + 120/8 Seagate 7200.7 NEC ND-3550A 16x DVD±RW + Lite-On 52x24x CD-RW Antec Sonata case // 480W Antec TruePower personal bests \|\| Aq'3: 46796 \| 3D'01: 20461 \| 3D'03: 6336 \| 3D'05: 2677 \| PC'04: 4605 \| PC'02: 7691,9092,1250

Dec 19, 2002, 02:23 PM	#5
bocybo DriverHeaven Junior Member Join Date: Jul 2002 Posts: 89 Rep Power: 0	Actually, with a true 333FSB motherboard such as the Nforce2, you can have a 333MHZ memory bus AND 333MHz CPU bus. The new athlons(2600 and up) are all capable of running a syncronized 333MHz bus.

Dec 19, 2002, 04:50 PM	#6
Zarathustra Elite Bastard Join Date: May 2002 Location: The Confederacy Posts: 841 Rep Power: 0	Vamp is correct. The AMD system bus isn't wide enough to warrant running the memory at a faster speed than the FSB. Intel is different though, it has enough bandwidth to benefit from faster memory. So the moral of the story is to run AMD synced Intel asynced

Dec 20, 2002, 04:18 PM	#8
bocybo DriverHeaven Junior Member Join Date: Jul 2002 Posts: 89 Rep Power: 0	Sorry didnt see it at first. But you still have to make sure to get a motherboard that will support the 333MHz FSB. Some will some wont. I would reccomend the Asus A7N8X. __________________ Barton 2500 @ 11.0x215 Epox 8RDA+ 1GB Corsair PC3200 ATI Radeon 9800 Pro @ 420/380 SB Audigy Lite-on 52x32x52 Maxtor 120GB ATA133

Dec 20, 2002, 08:41 PM	#9
Matth Flash Banner Hater Join Date: Jun 2002 Location: UK Posts: 3,426 Rep Power: 93 System Specs	If you have a "Throughbred unlock" BIOS (no idea how they do that), then maybe you could lower the multipler, and run a slower version at 333 FSB, and lower the multipler to aviod a 25% overclock unless it really can take it With an AGP 8x card, running memory async at 333, FSB 266 might be worthwhile, for an increase in RAM-AGP throughput if AGP textures are ever used.

Dec 20, 2002, 08:54 PM	#10
schmegma DriverHeaven Newbie Join Date: Nov 2002 Posts: 3 Rep Power: 0	Maybe the theory of it all says one thing, but I can attest to the 4:5 ratioing to get 333 RAM bus on a 266 FSB processor does increase performance. I have a 2100+ locked, running 266(133) with 333 running 333 and it does increase over running the DDR at 266. Granted, yes I agree I would be better off running a lower multiplier and getting the 333 FSB and then dropping to the 1:1 mem:cpu ratio and having sync operation. All I am saying is there are gains to be had running 333 DDR bus in a 266 FSB system, even if the XP shouldn't benefit from the additional bandwidth in theory. I can post Sanda info later once I get home if folks want it.

Dec 20, 2002, 11:11 PM	#11
Matth Flash Banner Hater Join Date: Jun 2002 Location: UK Posts: 3,426 Rep Power: 93 System Specs	In some cases, you NEED to clock the ram faster..... DDR-sync transfers as fast as the FSB can handle ONCE IT STARTS, but the setup time of DDR is ridiculous! So unless you can use "aggressive" timings at 266 sync, and have to back out of them at 333 async, you may be gaining from faster setup cycles. I also read somewhere that KT333 (and KT400) handles async RAM/FSB exceptionally well, while the nForce 2 recommends sync mode