Graphics IGPs and shared memory question

Was wondering whether modern IGPs use up all the memory you allocate to it in the bios or whether it gets allocated on the fly UP TO the amount set in the bios. Essentially if I set Shared memory in bios to 256MB would that amount be exclusive to the IGP or can some of it be used as system ram if the IGP does not require the whole 256MB? Does it depend on the specific IGP or do all the latest ones allocate memory on the fly e.g. 690G, 7050, G35 etc.

Renoir

 

Sorry to be be more helpful, but I'll I know is that it depends on the video card.

 

I *think* that it will use it all the time. As it seams that people with an IGP complain about the system not reporting its full amount of memory and asking if they have bad ram. and that happens at times when the system is not under a load of some kind.

 

It depends on the Igp, the 7050,7025 can be set to use 256 mb of the ram and can use anther 256 mb of ram with out telling you. but thr ati igp i think has memory built in.

 

It'll preallocate a memory partition in the BIOS so there's no overlap. It's not clever enough to share it on the fly.

 

From what I've read Bindi that's not always the case. For example the intel website says it's newer IGPs support Dynamic Video Management Technology (DVMT) which means some memory is fixed while some is allocated dynamically by the graphics driver. TechARP's bios guide backs this up by recommending selecting 8MB of pre-allocated memory while letting the rest be allocated on the fly by the graphics driver if the IGP supports DVMT. I'm not sure if AMD or Nvidia's chipsets support similar technologies but DVMT sounds basically the same as Hypermemory or turbocache does it not? I assume I've read this all right but perhaps I'm missing something?