Вообще, я думаю, больше 2 гб не получится завести.
А так в BIOS параметр "Memory Remap Feature " ставится Enable и для правильного определения памяти включаются функции S/W Memory Hole Remapping и H/W Memory Hole Remapping.

Нет, не знал о данном параметре в БИОС. Попробую. А это ничем не чревато в последствии?

Все телодвижения с BIOS или реестром системы пользователь совершает на свой страх и риск.
(С) из неопубликованной библии юзера

На никсе для данной платы увидел ссылку "в зависимости от типа процессора". показалось забавным, однако кроме Ссылка >> ничего по теме не увидел...

If you're only running a 2800+ or Sempron, it may be worthwhile to spend $200 to $300 for a faster processor, but ultimately, the platform is going to be the limiting factor. No dual core processors are planned for 754, and although PCIe may appear in a few motherboards, we have a hard time recommending such an option. It's also worth noting that the maximum supported RAM on Socket 754 motherboards is 3GB, meaning that true 64-bit support is somewhat debatable. For most Socket 754 owners, we'd say stick with what you have until you're no longer satisfied with the performance, and then upgrade to a new platform. For those who are looking to buy a new computer, we'd urge you to stay away from Socket 754 unless budget is the overriding concern. It's not necessarily a bad platform, but $50 more would allow you to upgrade to Socket 939, which we feel is the better choice.

Особенно понравилась фраза:

For those who are looking to buy a new computer, we'd urge you to stay away from Socket 754 unless budget is the overriding concern.