DDR2 Ratios and AM2 Processors

New DDR2 Memory Ratios

One interesting aspect that turned up during our testing and initial information about the AM2 processors from AMD was their change in the way the memory multipliers are handled.  While DDR2-800 speeds are only officially support on two models (the FX-62 and X2 5000+), you can expect users to be setting the memory dividers differently if they can find a way to do so in the motherboards BIOS’.  What we found though was that not all DDR2 memory speeds are created equally.

The basic formula for finding the final DDR2 memory speed on a system configuration is as follows: Reference clock x Multiplier = Processor speed / Memory Divider = Memory DIMM Speed

So, for a 2.8 processor, like our FX-62 sample we have here, the math is: 200 MHz x 14 = 2800 MHz / 7 = 400 MHz DDR2 or DDR2-800.  However, for the 5000+ processor, which runs at 2.6 GHz, it also uses a 7x memory divisor, resulting in a slightly lower 371.42 MHz clock or DDR2-742 speed.  This table below offers a few other examples:

CPU Speed

Multiplier

Memory Divisor

Resulting DDR2 Speed

2.0 GHz

10x

5

400 MHz

2.2 GHz

11x

6

366.66 MHz

2.4 GHz

12x

6

400 MHz

2.6 GHz

13x

7

371.42 MHz

2.8 GHz

14x

7

400 MHz

3.0 GHz

15x

8

375 MHz

3.2 GHz

16x

8

400 MHz

You can see that some of the AM2 processors will have DIMM speeds below what the motherboard BIOS settings are actually telling them they are getting and this will likely cause some confustion among users.  We will have to wait and see how the performance numbers show this difference will affect the end user. 

The Rest of the AM2 Lineup

As I mentioned before, though we only have the FX-62 processor for testing, a total of 15 different AM2 processors are launching today under the FX, X2, Athlon 64 and Sempron brands.  This handy-dandy table below details their specs, cache sizes, voltages, transistor count and prices. 

Model Number

Freq

L2 cache

DDR2 Spec

Voltage

Max TDP

Die Size

Transistors

Price $

FX-62

2.8 GHz

1MB x 2

DDR2-800

1.35-1.40v

125W

230 mm^2

227.4 M

1031

X2 5000+

2.6 GHz

512KB x 2

DDR2-800

1.30-1.35v

89W

183 mm^2

153.8 M

696

X2 4800+

2.4 GHz

1MB x 2

DDR2-667

1.30-1.35v

89W*

230 mm^2

227.4 M

645

X2 4600+

2.4 GHz

512KB x 2

DDR2-667

1.30-1.35v

89W*

183 mm^2

153.8 M

558

X2 4400+

2.2 GHz

1MB x 2

DDR2-667

1.30-1.35v

89W*

230 mm^2

227.4 M

470

X2 4200+

2.2 GHz

512KB x 2

DDR2-667

1.30-1.35v

89W*

183 mm^2

153.8 M

365

X2 4000+

2.0 GHz

1MB x 2

DDR2-667

1.30-1.35v

89W*

230 mm^2

227.4 M

328

X2 3800+

2.0 GHz

512KB x 2

DDR2-667

1.30-1.35v

89W**

183 mm^2

153.8 M

303

A64 3800+

2.4 GHz

512KB

DDR2-667

1.30-1.35v

62W

103 mm^2

81.1 M

290

A64 3500+

2.2 GHz

512KB

DDR2-667

1.30-1.35v

62W**

103 mm^2

81.1 M

189

Sempron 3600+

2.0 GHz

256KB

DDR2-667

1.30-1.35v

62W

103 mm^2

81.1 M

123

Sempron 3500+

2.0 GHz

128KB

DDR2-667

1.30-1.35v

62W

103 mm^2

81.1 M

109

Sempron 3400+

1.8 GHz

256KB

DDR2-667

1.30-1.35v

62W**

103 mm^2

81.1 M

97

Sempron 3200+

1.8 GHz

128KB

DDR2-667

1.30-1.35v

62W**

103 mm^2

81.1 M

87

Sempron 3000+

1.6 GHz

256KB

DDR2-667

1.30-1.35v

62W**

103 mm^2

81.1 M

77

* = Available in a Energy Efficient model @ 65W TDP
** = Available in Energy Efficient / Small Form Factor model @ 35W TDP

AM2 CPUs will be available in prices ranging from $77 all the way up to over $1000!  This all encompassing strategy will surely mean an end to the S939 platform rather quickly, though AMD of course is promising to support it as long as their partners demand.  That being said, there will be no more S939 processor releases period; all users looking for a new system will want to put the AM2 option at the top of their list if upgradability is a concern at all. 

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