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GeForce GT 640 DDR3 vs GeForce GTX 650

Intro

The GeForce GT 640 DDR3 comes with a clock frequency of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also makes use of a 128-bit bus, and uses a 28 nm design. It is comprised of 384 SPUs, 32 Texture Address Units, and 16 ROPs.

Compare those specs to the GeForce GTX 650, which features a core clock speed of 1058 MHz and a GDDR5 memory speed of 1250 MHz. It also features a 128-bit bus, and makes use of a 28 nm design. It features 384 SPUs, 32 TAUs, and 16 ROPs.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GTX 650 64 Watts
GeForce GT 640 DDR3 65 Watts
Difference: 1 Watts (2%)

Memory Bandwidth

In theory, the GeForce GTX 650 is 40% faster than the GeForce GT 640 DDR3 overall, because of its greater data rate. (explain)

GeForce GTX 650 80000 MB/sec
GeForce GT 640 DDR3 57024 MB/sec
Difference: 22976 (40%)

Texel Rate

The GeForce GTX 650 will be a little bit (approximately 18%) faster with regards to AF than the GeForce GT 640 DDR3. (explain)

GeForce GTX 650 33856 Mtexels/sec
GeForce GT 640 DDR3 28800 Mtexels/sec
Difference: 5056 (18%)

Pixel Rate

The GeForce GTX 650 is a little bit (approximately 18%) faster with regards to AA than the GeForce GT 640 DDR3, and capable of handling higher screen resolutions more effectively. (explain)

GeForce GTX 650 16928 Mpixels/sec
GeForce GT 640 DDR3 14400 Mpixels/sec
Difference: 2528 (18%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

Price Comparison

GeForce GT 640 DDR3

Amazon.com

GeForce GTX 650

Amazon.com

Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

Specifications

Model GeForce GT 640 DDR3 GeForce GTX 650
Manufacturer nVidia nVidia
Year June 2012 September 2012
Code Name GK107 GK107
Fab Process 28 nm 28 nm
Bus PCIe 3.0 x16 PCIe 3.0 x16
Memory 2048 MB 2048 MB
Core Speed 900 MHz 1058 MHz
Shader Speed 900 MHz 1058 MHz
Memory Speed 1782 MHz (3564 MHz effective) 1250 MHz (5000 MHz effective)
Unified Shaders 384 384
Texture Mapping Units 32 32
Render Output Units 16 16
Bus Type DDR3 GDDR5
Bus Width 128-bit 128-bit
DirectX Version DirectX 11.0 DirectX 11.0
OpenGL Version OpenGL 4.2 OpenGL 4.3
Power (Max TDP) 65 watts 64 watts
Shader Model 5.0 5.0
Bandwidth 57024 MB/sec 80000 MB/sec
Texel Rate 28800 Mtexels/sec 33856 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 16928 Mpixels/sec

Memory Bandwidth: Memory bandwidth is the max amount of data (counted in MB per second) that can be transported across the external memory interface within a second. It is calculated by multiplying the card's interface width by its memory clock speed. In the case of DDR type RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This figure is worked out by multiplying the total amount of texture units of the card by the core speed of the chip. The better this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly record to the local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the number of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on lots of other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.

Comments

3 Responses to “GeForce GT 640 DDR3 vs GeForce GTX 650”
RTh says:
woow... look @ the TDP
Johnny says:
Certainly going for the GTX 650 is a better choice if you are choosing between these two cards. Why to chhoose:
The higher bandwidth & GDDR5 bus (over the outdated DDR3 bus)
And even the Power consuption is lower in the GTX 650 with much better performance.
I have both cards.
Step 3 says:
I have both , the MSI GTX650 with 1gb ddr5 and an OEM HP GT640 with 4gb ddr3 . Passmark scores for the GTX650 is only 30 or so points higher then the GT640. BUT, I can use MSI's Afterburner to push the score to about 200 points higher then the stock out of the box settings. So overclocking the GTX yields greater results, but the stock settings are very similar between the two cards.
HOWEVER ! Both needed MORE power to achieve full performance. They both worked with the factory Dell 760 305w PSU, but both achieved much higher Passmark scores when a higher output PSU (Thermaltake 700w) was installed. Approx. 600 + - points higher, which is a HUGE improvement. This is not due to Dell limiting the PCI-E slots power, as the GT640 does not use a PCI-E power cable, as does the GTX650. The GT640 gets all of it's power through the PCI-E slot. So if you think you can run a GT640 with a lower powered PSU, you might miss out on a major part of the cards abilities. SO don't let the low TDP fool you, you still need a decent PSU to properly power these two cards to achieve their full potential. What the low TDP does allow, is the ability to use the cards with a smaller PSU to start off, which will let you determine if you are able to run the card fully with your current PSU. Don't assume you're getting all of it's capabilities, you'll need to run some benchmark tests and compare your cards score vs other average scores. If you are WAY off, you'll probably benefit with a PSU upgrade. This way, you can see if the PSU you have will get the job done before spending the coin on a larger PSU. To give an example, I still have the DEll supplied HD3450, which achieves approx. the same Passmark score as the GT640 when using the stock Dell PSU. The GT640 smokes the HD3450 when the larger PSU is installed.

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