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DRAM Frequency to CPU Freq. Ratio?

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Name: zcubed
Date: November 16, 2005 at 22:47:57 Pacific
OS: Win XP Pro w/SP2
CPU/Ram: 2.6 GHz OC to 2.9 P4/ 1 G
Comment:

The overclocking utility on my motherboard has a feature which lets me decide the CPU to DRAM Freq. Ratio. There are 4 settings. 2:1, 3:2, 6:5, 1:1. I have a P4 2.6 @2.9 800FSB and 512MBx2(1GB) of DDR400 PC3200. The frequency ive overclocked the CPU to is 222(originally 200). Could someone please explain what this ratio does? Also which one ud recommend.

Zo



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Response Number 1
Name: jam
Date: November 17, 2005 at 08:40:02 Pacific
Reply:

The ratio helps when running lower bus speed RAM with a higher FSB CPU, or to help with overclocking.

Ideally, you should run 1:1 ratio so that the RAM & CPU are in sync.

At 2:1 ratio, your RAM bus would be running at 50% of the CPU bus, but you'd be able to run PC1600 (DDR200) RAM with your 200MHz (800FSB) CPU...at 3:2 it would be running at 66.66% for PC2100 (DRR266)...at 6:5 it would be at 83.33% for use with PC2700 (DDR333).

When overclocking, your RAM may hold your CPU back, so if you were to change the ratio to 6:5, you could raise the CPU bus up to 240MHz & your PC3200 RAM would still be running at 200MHz.

ASUS A7N8X-X
Athlon XP 1800+
8.5 x 200MHz
1024MB PC3200 2.5-3-3-7
Asus A9550GE/TD 128MB
WinME/WinXP Pro SP2


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Response Number 2
Name: zcubed
Date: November 17, 2005 at 09:38:41 Pacific
Reply:

so which ratio should i choose for my specific RAM?

Zo


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Response Number 3
Name: pr3d
Date: November 17, 2005 at 09:39:39 Pacific
Reply:

1:1 is the perfect ratio for all ram

Why can't we put questions here?


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Response Number 4
Name: zcubed
Date: November 17, 2005 at 10:17:05 Pacific
Reply:

thanks a lot.

Zo


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Response Number 5
Name: jam
Date: November 17, 2005 at 10:29:32 Pacific
Reply:

Yes, 1:1 is what you should always strive for, but since you have your CPU o/c'd to 222MHz, your PC3200 RAM may not be able to handle that speed. So you'd either have to back off on the o/c, or change the ratio to 6:5. That will put your RAM at 185MHz & should allow for an even higher CPU FSB (240MHz+).

ASUS A7N8X-X
Athlon XP 1800+
8.5 x 200MHz
1024MB PC3200 2.5-3-3-7
Asus A9550GE/TD 128MB
WinME/WinXP Pro SP2


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Response Number 6
Name: zcubed
Date: November 17, 2005 at 16:24:19 Pacific
Reply:

thanks guys. 1:1 seems to be working fine. ill try o/cing it more once i get a new psu.

Zo


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Response Number 7
Name: roofrat
Date: December 27, 2005 at 10:22:37 Pacific
Reply:

So what would you suggest in this case? Overclock the cpu?

Number of CPUs 2 (1 Physical)

CPU#1 APIC ID = 0
Name Intel Pentium 4 640
Code Name Prescott
Specification Intel(R) Pentium(R) 4 CPU 3.20GHz
Family / Model / Stepping F 4 3
Extended Family / Model 0 0
Package LGA775
Core Stepping N0
Technology 0.09 µ
Supported Instructions Sets MMX, SSE, SSE2, SSE3, x86-64
CPU Clock Speed 2800.0 MHz
Clock multiplier x 14.0
Front Side Bus Frequency 200.0 MHz
Bus Speed 800.0 MHz
L1 Data Cache 16 KBytes, 8-way set associative, 64 Bytes line size
L1 Trace Cache 12 Kµops, 8-way set associative
L2 Cache 2048 KBytes, 8-way set associative, 64 Bytes line size
L2 Speed 2800.0 MHz (Full)
L2 Location On Chip
L2 Data Prefetch Logic yes
L2 Bus Width 256 bits

CPU#2 APIC ID = 1
CPU Name Intel Pentium 4 640 (logical unit)


Mainboard and chipset
Motherboard manufacturer ASUSTeK Computer INC.
Motherboard model P5ND2-SLI, 1.XX
BIOS vendor Phoenix Technologies, LTD
BIOS revision ASUS P5ND2-SLI ACPI BIOS Revision 0605
BIOS release date 05/06/2005
Chipset nVidia nForce4 SLI Intel Edition rev. A1
Southbridge nVidia nForce4 MCP rev. A3
Sensor chip IT 8712

Memory
DRAM Type DDR2-SDRAM
DRAM Size 4096 MBytes
DRAM Frequency 166.7 MHz
FSB:DRAM 6:5
CAS# Latency 4.0 clocks
RAS# to CAS# 5 clocks
RAS# Precharge 5 clocks
Cycle Time (TRAS) 15 clocks
Bank Cycle Time (TRC) 19 clocks
# of memory modules 4
Module 0 Corsair DDR2-SDRAM PC5300 - 1024 MBytes
Module 1 Corsair DDR2-SDRAM PC5300 - 1024 MBytes
Module 2 Corsair DDR2-SDRAM PC5300 - 1024 MBytes
Module 3 Corsair DDR2-SDRAM PC5300 - 1024 MBytes

Software
Windows version Microsoft Windows XP Professional Service Pack 2 (Build 2600)
DirectX version 9.0c



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Results for: DRAM Frequency to CPU Freq. Ratio?

How to change FSB:DRAM frequency? www.computing.net/answers/cpus/how-to-change-fsbdram-frequency/14546.html

o/c P4 www.computing.net/answers/cpus/oc-p4/12870.html

CPU/DRAM frequency www.computing.net/answers/cpus/cpudram-frequency/8122.html