2GB Z3 RAM, /3GB boot option and 32-bit Windows

mark_k · 08 December 2012, 22:27

One of the changes for WinUAE 2.5.0 was
- 64-bit build supports 2.5G address space, allowing up to 2G of Z3 expansion memory.

I'm just wondering if there's a reason why only the 64-bit build has support for that? Maybe a performance impact or something?

According to this page on the Microsoft site using the /3GB boot parameter can allow 3GB user-mode address space for programs which were linked with the /LARGEADDRESSAWARE option. When running large-address-aware 32-bit programs under 64-bit Windows, the program gets 4GB of address space. The Microsoft page mentions Windows Server 2003 SP1 providing up to 4GB; I guess the same applies to 64-bit Vista, 7, 8 too???

The advantage of having the 32-bit build able to support that much memory would be (apart from being useable on 32-bit OS) that JIT is supported.

Toni Wilen · 09 December 2012, 10:00

Not worth the trouble again. Just use 64-bit Windows, "every one" uses it since Windows 7.

Remember that everything that WinUAE needs to see must fit in that 2G or 3G address space. That includes _every_ DLL that program uses (Only memory mapped if already loaded by other programs), all buffers, all driver allocated buffers, WinUAE itself, buffers allocated by WinUAE.

Under 32-bit Windows too much reserved memory caused all kinds of strange and random errors when starting emulation, for example display failed initialize because lack of memory. (Slightly under 1G seems to be the max)

32-bit program running under 64-bit Windows: VirtualAlloc() seems to have 2G contiguous allocation size restriction. JIT requires that all Amiga memory can be addressed simply by adding offset to start of RAM. (Address zero of Amiga address space): 2G Amiga address space is the max. (which leaves ~1.7G left for Z3 space)

WinUAE has LARGEADDRESSAWARE option set.

08 December 2012, 22:27	#1
mark_k Registered User Join Date: Aug 2004 Location: Posts: 3,343	2GB Z3 RAM, /3GB boot option and 32-bit Windows One of the changes for WinUAE 2.5.0 was - 64-bit build supports 2.5G address space, allowing up to 2G of Z3 expansion memory. I'm just wondering if there's a reason why only the 64-bit build has support for that? Maybe a performance impact or something? According to this page on the Microsoft site using the /3GB boot parameter can allow 3GB user-mode address space for programs which were linked with the /LARGEADDRESSAWARE option. When running large-address-aware 32-bit programs under 64-bit Windows, the program gets 4GB of address space. The Microsoft page mentions Windows Server 2003 SP1 providing up to 4GB; I guess the same applies to 64-bit Vista, 7, 8 too??? The advantage of having the 32-bit build able to support that much memory would be (apart from being useable on 32-bit OS) that JIT is supported.

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09 December 2012, 10:00	#2
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,517	Not worth the trouble again. Just use 64-bit Windows, "every one" uses it since Windows 7. Remember that everything that WinUAE needs to see must fit in that 2G or 3G address space. That includes _every_ DLL that program uses (Only memory mapped if already loaded by other programs), all buffers, all driver allocated buffers, WinUAE itself, buffers allocated by WinUAE. Under 32-bit Windows too much reserved memory caused all kinds of strange and random errors when starting emulation, for example display failed initialize because lack of memory. (Slightly under 1G seems to be the max) 32-bit program running under 64-bit Windows: VirtualAlloc() seems to have 2G contiguous allocation size restriction. JIT requires that all Amiga memory can be addressed simply by adding offset to start of RAM. (Address zero of Amiga address space): 2G Amiga address space is the max. (which leaves ~1.7G left for Z3 space) WinUAE has LARGEADDRESSAWARE option set.

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