GAMS is available in a 32 bit and a 64 bit version for Windows. The 64 bit version requires the presence of a 64 bit version of Windows to operate properly - just having a 64 bit processor is not sufficient. The 32 bit version of GAMS will work on both versions of Windows, but the operating system limits the GAMS process to ~ 1.7 GB (Windows 32 Bit) or ~ 4 GB (Windows 64 Bit).

In general, you should not expect a performance improvement from the 64 bit version. The benefit will be in being able to solve larger models. Please note that the 64bit version of GAMS may require up to 35% more RAM than the 32 bit version. Sometimes it may be advantageously to run the 32 bit version of GAMS on a 64 bit version of the operating system.

If you are not sure, which version of the operating system is installed on your machine, click on:

• (Vista:) Start → Computer → System Properties (right mouse tab) and check the information about the System type

• (Windows XP and 2003:) My Computer (right mouse tab) → Properties → General: The 64 bit versions have an entry there, which reads: “ .. x64 Edition” → Shortcut: Just click on the 'Windows-key' and 'Break' to get to System Properties

The command line tool systeminfo, which is included in XP and more recent versions of Windows, provides an exhaustive snapshot about important system parameter. Below is an example outout:

Microsoft Windows [Version 5.2.3790]
(C) Copyright 1985-2003 Microsoft Corp.

X:\temp>systeminfo

Host Name:                 XYZ
OS Name:                   Microsoft(R) Windows(R) Server 2003, Standard Edition

OS Version:                5.2.3790 Service Pack 2 Build 3790
OS Manufacturer:           Microsoft Corporation
OS Configuration:          Member Server
OS Build Type:             Uniprocessor Free
Registered Owner:          XYZ
Registered Organization:   GAMS Development Corp.
Product ID:                69712-XXX-YYYYYYY-ZZZ
Original Install Date:     7/6/2006, 12:44:48 PM
System Up Time:            N/A
System Manufacturer:       Microsoft Corporation
System Model:              Virtual Machine
System Type:               X86-based PC
Processor(s):              1 Processor(s) Installed.
                           [01]: x86 Family 15 Model 33 Stepping 2 AuthenticAMD~1994 Mhz
BIOS Version:              A M I  - 9000520
Windows Directory:         C:\WINDOWS
System Directory:          C:\WINDOWS\system32
Boot Device:               \Device\HarddiskVolume1
System Locale:             en-us;English (United States)
Input Locale:              en-us;English (United States)
Time Zone:                 (GMT-05:00) Eastern Time (US & Canada)
Total Physical Memory:     1,023 MB
Available Physical Memory: 700 MB
Page File: Max Size:       2,473 MB
Page File: Available:      2,202 MB
Page File: In Use:         271 MB
...