I've got an Asus Radeon 6450 (512 mb DDR3). It's silent, but it seems too slow for Aero. Windows Experience Index for Aero is 3.0 while for Games it's 5.6. What's happening?

Seems pretty odd to me. Ignoring the benchmark, are you having any problems?

The slowest, bottom feeding Intel HD graphics on a Pentium can run Aero smoothly. So, you shouldn't have issues with a current gen discrete card.

It's fine now, but the entire desktop appeared to act in slow motion at some point. Not sure what was happening.

It's more likely some process or processes decided to bog down the CPU and ground all other actions to a halt. To you, it might have just looked like a slow display refresh.

It's a Q9450 that I've used for years, so that seems unlikely.

How long you've owned the cpu is irrelevant. I'm talking about software/processes running in the background that may be the cause of the bog down. Maybe a recent revision/update of some antivirus software, a browser update, an incompatible plug-in for a browser, a Catalyst update, etc...that is causing these wtf moments.

Try running the process monitor in the background and take a look at cpu utilization when things bog down.

Say, your card doesn't happen to have a 32-bit memory bus does it? There are apparently some non-reference 6450s out there using a 32-bit interface, and people have reported performance issues with them. It looks like ASUS offers two silent 6450s, one with 1GB of 64-bit DDR3 memory, and another with 512MB of 32-bit DDR3. I can not fathom why they would cripple an otherwise decent modern graphics card with a 32-bit memory interface, but they apparently decided it was a good idea. I don't imagine it saved them all that much in production costs. The user reviews at Newegg for the 32-bit version don't seem to appreciate it all that much.

If that's the case, it might be your best bet to replace the card with a different 6450 that hasn't been gimped, or some other card. I actually have an ASUS card and it works great, but it's an HD 4670 with 128-bit DDR3. It's generally a good idea to look over the detailed specs of a card when buying it to make sure it hasn't been significantly crippled compared to the reference design. The amount of memory probably isn't going to make much of a performance difference on these lower-power cards, but the type of memory and its interface could.

It does.

I know. I did check 6450 benchmarks, but I did not expect someone to halve the memory bandwidth.
I knew it had 512 mb memory, but I didn't know it had only a 32 bit bus. It isn't even mentioned on the box.

Sometimes the desktop feels sluggish. It's a bit hard to quantify. Things like scrolling, window switching.

Wow 32bit ddr3 memory what a disaster. The ddr3 versions of the HD 6450 are pretty bad to begin with, and this one has only 1/3 the bandwidth of the reference ddr3 version, which should pretty much directly translate to only 1/3 the performance. Any half-current IGP will easily beat this (intel hd, hd2000, brazos...).
You could try overclocking if that works (don't even bother with the core clock, just memory) - I think chances of overclocking ddr3 memory on such cards should be pretty decent, with some luck you might get that 550Mhz up to the reference 800Mhz. This should result in linear if not superlinear increase in performance corresponding to the memory clock increase.
For HTPC, it is pretty well known not even the 64bit ddr3 HD6450 cards can do all the video features though, so it probably won't help all that much.
(btw the reason the 512MB ddr3 cards are only 32bit is most likely because the cheapest ddr3 memory chips you can get nowadays are the 2 gbit ones. And for 512MB that works out to be 2 chips, and since you can only get the chips with 8 or 16bit interface width that means 32bit interface for 2 chips.)

What R6450s have non-DDR3 memory?
Anyway, I've returned it and got a R6570. Didn't try it yet though.

Only the review edition . A shame really since the performance difference is rather large. But I guess they think everybody wanting faster-than-IGP performance opts for higher end cards anyway.

That should solve all problems even if it only has low-clocked ddr3 - it should have definitely 128bit memory interface .

Sounds like fraud...

I'm a bit confused with GDDR5 vs DDR3.
DDR1 is 2x data rate. DDR2 is 4x. DDR3 is 8x, right?
Isn't GDDR5 also 8x?
If so, why is it so much faster?

Hi, ref memory speeds, the original SDR RAM could only transfer once per clock cycle, hence the term retrospectively applied, Single Data Rate.
In the quest for memory bandwidth they came up with DDR, Double Data Rate, that can make two data transfers per clock cycle, once on the rising clock signal and once on the falling.
As I understand it GDDR2, GDDR3 and GDDR4 are more-or-less faster standards for DDR, same idea and operation just revised timing / voltage to allow faster operation.
I think GDDR5 is able to transfer 4 times per clock, I.E. 900MHz base clocked ram will be advertised as 3600MHz. This will give GDDR5 twice to memory bandwidth for a given baseclock/interface width over GDDR2/3/4. Do often need to check what the given memory frequency is, if is the base clock or the effective clock, usually they give the effective clock as bigger numbers = better!

There is a table on this page on Anandtech that lists some cards with interface widths, memory clocks and effective clocks and the bandwidth this translates to, might help.

Regards, Seb

Just installed the R6570. Windows Experience Index for Aero (and games) is now 6.7. Haven't noticed any issues so far. Memory bandwidth is 21.3 gbyte/s (1333 mbit/pin).