Sideport memory and shared system memory in RS780 IGP

[PingSpike]

I never really paid much mind to integrated chipsets, but I just picked up a cheapo little notebook/netbook and opted for the an amd solution with hd3200 in the end.

However, I noticed that some motherboards using this chipset include separate memory for the IGP. I believe its called sideport memory. I don't think the little msi lappy I bought has it but after looking at the amd gpu comparison wiki it suggests that this uses a 32-bit memory bus for the sideport. I don't understand how this would be advantageous. With the IGP I understand the system memory runs at 64-bit and 128-bit in dual channel.

So system memory bandwidth with DDR2800 should be (400x2x64) / 8 = 6.4GB/s, or 12.8GB/s with dual channel.

I can't figure out what the sideport memory runs at (I've seen GPU-Z with 266 and 333 listed but the fields for memory generally looked missed/messed up for these chips so who knows?) but it would have to be pretty high a rate to make up for the 32-bit memory bus.

But this sideport option is listed as a performance boosting addition? Am I missing something? Latency when accessing the system ram perhaps?

 

[Phil1977]

You are correct, sideport does very little...

In benchmarks you might gain a few fps that's it...

You are much better off picking are more basic mainboard (like a AMD 770) and getting a dedicated graphics card.

 

[VirtualLarry]

You are correct, sideport does very little...

In benchmarks you might gain a few fps that's it...

You are much better off picking are more basic mainboard (like a AMD 770) and getting a dedicated graphics card.

In a notebook?

OP, sideport memory helps to reduce the performance drop experienced by having the onboard video access main memory. It is not to speed up the IGP faster than main memory can handle.

 

[Phil1977]

I have not come across a notebook with sideport yet...

You mentioned notebooks specifically. Which one are you refering to?

Most notebooks have intel chipset graphics (90%?). Spend a bit more and you allready get a dedicated ATI or Nvidia graphics chip...

AFAIK sideport is found on 780/785 chipset desktop mainboards.

There are only very few notebooks / netbooks that even have AMD chipsets. And the few I have come across at work did not have sidport. Doesn't make sense anyway as at that level every penny counts, so why put sideport in a budget notebook.

 

[PingSpike]

I asked for some benchmarks from people that had HD3200 on laptops. Some one responded who had an acer 5534. It lists 256mb onboard on acer's website. I agree it seems rare, but since he was the only one to respond with the HD3200 I got to wondering about what kind of effect the sideport had on performance.

I don't really know the breakdown, but most amd based notebooks now available have the HD3200 that comes with the RS780 chipset. It is true that AMD doesn't have as competitive offerings for notebook cpus and since intel has shut the door on nvidia chipsets new notebooks are mostly stuck with at best the 4500hd.

 

[Kuzi]

For people that are happy playing older games at low res/settings, sideport memory would give them a noticeable boost, something around 25%. Yeah it is still only a few fps difference, for example going from 20fps to 25fps.

I believe the memory bus for sideport memory is 64bit not 32bit.