Is my system using only half of a VRAM?

[Zead]

$ lspci -v -s 01:00.0
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV516/M64 [Mobility Radeon X2300] (prog-if 00 [VGA controller])
Subsystem: ASUSTeK Computer Inc. Device 1449
Flags: bus master, fast devsel, latency 0, IRQ 16
Memory at d0000000 (32-bit, prefetchable) [size=128M]
I/O ports at a800 [size=256]
Memory at fa9f0000 (32-bit, non-prefetchable) [size=64K]
Expansion ROM at fa9c0000 [disabled] [size=128K]
Capabilities: <access denied>
Kernel driver in use: radeon

Some websites say X2300 has only max 128MB, but some says 256MB... Windows told me I have 256MB too.

Maybe Windows detected wrong memory size?