Really dumb FSB Question

Kemal · Jun 16, 2005, 09:49 PM

So, I just got this AMD Athlon XP 3000+ Socket A Processor to last me through the summer until my next 'big' upgrade in the fall. One of the reasons I purchased it is so that I can take advantage of its 400mhz FSB, which my ASUS A7N8X-Revision 2.0 supports.

I have two 512mb PC3200 sticks of ram running in dual-channel, and an additional 256mb stick as well.

Here's a summary of the cpu-configuration screen in my bios:

CPU External Freq. (mhz) = 200mhz
CPU Frequency Multiple = 10.5x
Memory Frequency = 100%
Resulting Frequency = 200mhz

When I start up the computer, it displays that my FSB is 200.

So I guess my question is, how do I get my FSB to be 400mhz?

Zelig · Jun 16, 2005, 10:02 PM

FSB is 200 MHz, RAM is running at DDR400... everything's fine.

Kemal · Jun 16, 2005, 10:09 PM

Quote:

Originally Posted by Zelig

FSB is 200 MHz, RAM is running at DDR400... everything's fine.

Something just doesn't make a whole lot of sense to me, the motherboard box says "400mhz FSB" the CPU page says "400mhz fsb".....yet, 200mhzfsb=400mhz fsb?

riles9262 · Jun 16, 2005, 11:09 PM

Athlon cpu's are double pumped, in other words bringing the fsb to 400mhz. Speedwise, it's still 200mhz, it's just a matter of when the cpu is able to access data during its clock cycle. Take a look at this guide in the double, quad pump and ddr explanation http://www.directron.com/fsbguide.html#part3

**dj_stick** · Jun 17, 2005, 12:09 AM

athlon CPUs and DDR (daul data rate) ram work at effectively twice the speed of the FSB clock, so 200mhz FSB = 400mhz effective
p4 cpus work at 4 times the FSB clock, 200mhz fsb = 800mhz effective

Matth · Jun 17, 2005, 04:19 PM

Yes, Double pumped, transferring on leading and trailing edges in full burst mode, though DDR is generally only something like 30% faster than SDR in real terms, as the latency is not reduced (typically, it may eve be increased compared to the best that SDR could do)

So the old Athlons and Durons ran at 200FSB (100 clock), and while the could handle 200FSB with a DDR chipset, the early chipsets used SDRAM, so the DDR capability was not realized.

With the 266FSB (133 clock), there came a mix of SDRAM (PC133) operation, and DDR.

From 333FSB to 400FSB, it was exclusively DDR, with the actual clocks at 166 or 200.

Of course, extra cation is now needed in quoting either the clock speed (200) or the FSB (400), as it can result in confusion with the older 200FSB (100 clock)

Jun 16, 2005, 09:49 PM	#1
Kemal DriverHeaven Lover Join Date: Nov 2002 Posts: 166 Rep Power: 0	Really dumb FSB Question So, I just got this AMD Athlon XP 3000+ Socket A Processor to last me through the summer until my next 'big' upgrade in the fall. One of the reasons I purchased it is so that I can take advantage of its 400mhz FSB, which my ASUS A7N8X-Revision 2.0 supports. I have two 512mb PC3200 sticks of ram running in dual-channel, and an additional 256mb stick as well. Here's a summary of the cpu-configuration screen in my bios: CPU External Freq. (mhz) = 200mhz CPU Frequency Multiple = 10.5x Memory Frequency = 100% Resulting Frequency = 200mhz When I start up the computer, it displays that my FSB is 200. So I guess my question is, how do I get my FSB to be 400mhz? __________________ ASUS A7N8X Rev 2.0 AMD Athlon XP 3000+ 1gb PC3200 DDR (512mb PC3200x2) + 256mb Radeon X800 Pro Sound Blaster Audigy 2 Windows XP SP 2

Jun 16, 2005, 10:02 PM	#2
Zelig HardwareHeaven Extreme Member Join Date: Jun 2003 Location: Canada Posts: 3,187 Rep Power: 71 System Specs	FSB is 200 MHz, RAM is running at DDR400... everything's fine. __________________ --

Jun 16, 2005, 11:09 PM	#4
riles9262 Driverheaven brewmaster Join Date: Oct 2002 Location: British Columbia, Canada Posts: 4,842 Rep Power: 72 System Specs	Athlon cpu's are double pumped, in other words bringing the fsb to 400mhz. Speedwise, it's still 200mhz, it's just a matter of when the cpu is able to access data during its clock cycle. Take a look at this guide in the double, quad pump and ddr explanation http://www.directron.com/fsbguide.html#part3 __________________ A beer a day keeps the doctor away.

Jun 17, 2005, 04:19 PM	#6
Matth Flash Banner Hater Join Date: Jun 2002 Location: UK Posts: 3,426 Rep Power: 93 System Specs	Yes, Double pumped, transferring on leading and trailing edges in full burst mode, though DDR is generally only something like 30% faster than SDR in real terms, as the latency is not reduced (typically, it may eve be increased compared to the best that SDR could do) So the old Athlons and Durons ran at 200FSB (100 clock), and while the could handle 200FSB with a DDR chipset, the early chipsets used SDRAM, so the DDR capability was not realized. With the 266FSB (133 clock), there came a mix of SDRAM (PC133) operation, and DDR. From 333FSB to 400FSB, it was exclusively DDR, with the actual clocks at 166 or 200. Of course, extra cation is now needed in quoting either the clock speed (200) or the FSB (400), as it can result in confusion with the older 200FSB (100 clock)