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Topic Title: HTT vs. RAM Speed
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Created On: 06/29/2004 10:28 AM
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 06/29/2004 10:28 AM
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marausch
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In the spirit of "the only dumb question is the one you don't ask":

If HTT runs at an effective 800MHz, why are BIOS memory frequencies "choked" at 200MHz?

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 06/29/2004 12:26 PM
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Greyhound
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QUOTE If HTT runs at an effective 800MHz, why are BIOS memory frequencies "choked" at 200MHz?
800MHz is actually the HT-links' physical clockspeed - it's effective speed is 1600MHz

The memory has NOTHING to do with the processors' Hypertransport-link(except maybe for the fact that it can be accessd by another processor via HT on an Opteron 2xx/8xx multiprocessor setup).
The Athlon 64 has an integrated(on-die) memory-controller with its own dedicated 64-bit(or 128-bit on Socket 939) path which is completely independent from the HT-link.

The processors' Hypertransport-link solely serves as a connection between the processor and the chipset/rest of the system, excluding the memory.

As far as clockspeeds are concerned, the HT-links clock is derived from the processors' 200MHz base-clock while the memory frequency is derived from the CPU's core-clockspeed:

Base-clock(200MHz)---[core-clock multiplier]--->CPU core-clock---[memory divider]--->Memory-clock
I
I>[Hypertransport-multiplier]
I
Hypertransport-clock

For your system(A64 3200+, model 4):

Base-clock(200MHz)---[x10.0]--->2000MHz---[/10](for DDR400 memory)--->200MHz(400MHz effectively - it's DDR, remember?)
I
I>[x4.0]
I
800MHz(1600MHz effectively - DDR strikes again )

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 06/29/2004 01:43 PM
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marausch
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Thanks, Grey, for the usual cogent reply.

I feel like I stayed at a Holiday Inn®

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"Faster, faster, faster, until the thrill of speed overcomes the fear of death!"

Hammerhead

Gigabyte K8VNXP (BIOS F10), Clawhammer F4 3200+ (OC=210x10)
2 x 120GB Seagate SATA RAID-1
ATI Radeon X800,
Ultra 512MB PC3200 DDR400 (x2) (2.7v)
Plextor 708A DVD +R, Plextor 716 DL DVD
Antec 400W ATX PSU, Planar 19" FP moni
MS Wireless KB, Logitech MX510 Mouse
Logitech Extreme 3D Pro Joystick
XP Pro OS, SP2
 06/30/2004 12:06 AM
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Sephiroth311
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Every time he relies to a post I feel like the hand of God has touched my mind...

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