Why does the SK-7 perform worse than SLK-800?

Let's see, they both look alike, have the same thin-fin construction, in fact the SK-7 is wider than the SLK-800, and are made by the best heatsink company in the world

Why does the SLK-800 outperform the SK-7? Is it a better soldering job on the fins, thinner base, tighter clips, what??

I don't think that they do a better soddering job on one model verus another. I guess its just the weight of the copper (484g against 550g) that can make the diff. Else the 800 does probably have more surface, therefore more dissipation.

A.

I believe Ange is right. The SLK800 has more total surface area.

Ange said:

I don't think that they do a better soddering job on one model verus another. I guess its just the weight of the copper (484g against 550g) that can make the diff. Else the 800 does probably have more surface, therefore more dissipation.

A.

Click to expand...

I think the mass of copper is 485 g for SK7 and 505 g for SK-800.

Their dimensions are different, althought they may look similar, and that difference means a difference in surface area and cooling ability. There is only a slight difference in performance too.

hitechjb1 said:

Some analysis between the SK7 and SK-800:

The mass of the copper:
SK7 = 485 g
SK-800 = 505 g (4% more)

Both have 34 copper fins.

SK7 L W H = 85 65.5 42 mm
SK-800 L W H = 87 56.4 48 mm

Total surface area of copper fins just based on L x H estimate:
SK7 = 34 x 2 x 85 x 42 = 242760 mm^2
SK-800 = 34 x 2 x 87 x 48 = 283968 mm^2 (17% more)

Actual area should be about 20% smaller taking into account of tapering shape and central cut out for the clamp. But both have similar shape, so comparison seems to be fair.

So physically in term of Cu mass and surface area, the SK-800 has more.

The main difference in terms of air design between the two is that:

The SK-800 has a narrow solid base much smaller than the CPU die holder (more than half of the base is open), so the fan can suck the hot air around the CPU away through the fins.

The Sk7 has a larger solid base that covers a bigger area of the CPU die holder, I suspect the hot air around the CPU is not sucked out as effectively as the SK-800.

Click to expand...

Thanks, IMOG

...

But anyway, the difference between the two is only 0.02 C/W. I.e. a temperature difference of 0.02 C per Watt of the CPU power.

For a TBred B 2100-2600+, the power is around 50-70W. So the die temperature difference between the two is less than 1.4 C.

So I think the air cool overclockablitly between the two is not that significant since there are many other factors such as higher fan speed, acceptable noise, case cooling, ... that would override the small die temperature difference.

The price of a SK7 is 60% of a SK-800.