Dark Savant found an interesting article on Nerdly Pleasures about the version, release and demo history of Baldur's Gate:
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Baldur's Gate Version, Release and Demo History
Baldur's Gate is one of my most favorite games and has a surprisingly complex patching, release and demo history. I have written this blog article to help enlighten people on the version and patches available for the original game, significant physical releases and localization changes and finally the three demos of the game which were sold at some point. I will not discuss any unofficial patches (such as the Baldurdash and Dudleyville fixpacks), engine conversions (such as BG1Tutu or Baldur's Gate Trilogy) or Baldur's Gate: Enhanced Edition.
Version Number History
1.0.4309 - December 14, 1998: This is the original retail release of Baldur's Gate, which came on five CD-ROMs. If you want to obtain a physical copy of the original unpatched release, US Disc 1 must have the text "CD-C95-625-0" on its label. This version would only be released as 5 CDs.
1.1.4312, January 16, 1999 : Beta patch, presumably this was released to the public but due to a crash bug with save games it was problematic and quickly replaced. This patch has probably been lost to time.
1.1.4315, February 1, 1999 : Finalized version of the previous patch. The 5 CD release was updated with this patch, and all DVD releases will have this patch applied. Generally only disc 1 will differ between 1.0.4309 and 1.1.4315 with US releases of Baldur's Gate. The patch is available in an "English Version" and an "International Version". This version is notable for allowing the player to adjust the pathfinding nodes from a fixed 4000 to anything between 2000 and 32000.
1.3.5508, April 28, 1999 : The original release of the Tales of the Sword Coast Expansion on one CD-ROM. May be installed over an unpatched install of Baldur's Gate. If you want to obtain a physical copy of the original unpatched release, the US disc must have the text "CD-C95-898-0" on its label. The Expansion brings several improvements to the base game when it is installed.
1.3.5512, June 22, 1999 : The patch for Baldur's Gate with the Tales of the Sword Coast Expansion. The Expansion Pack's retail CD release was updated with this patch. The patch is available in a "North American English Version", an "International English Version" and an "International Non-English Version"
1.3.5521, August 8, 2001 : This patch came separately for Baldur's Gate and Baldur's Gate with with the Tales of the Sword Coast Expansions. The Baldur's Gate only patch came in an "English Version" and an "International Version", the Tales of the Sword Coast patch came in an "North American English Version", an "International English Version" and an "International Non-English Version". The patch is an executable replacement (BGMain.exe or BGMain2.exe) for fixing an issue with DirectX 7 or 8 and not being able to join a multiplayer game. Baldur's Gate was designed for DirectX 6, and this patch is not necessary or helpful if you are not using multiplayer.
1.3.5521, August 16, 2001 : The version was released as "Baldur's Gate: The Original Saga" and includes the Tales of the Sword Coast Expansion on three CD-ROMs. The version renumbering was due to changes in the engine to allow the game to decompress the resource files stored as compressed .BIFs on the CDs. Compressing the .BIF files was necessary to fit six discs worth of content onto three. As a result, The Original Saga will not be found on any US retail DVD, a single-layer DVD has more than enough space to fit the whole game plus the expansion without the need to resort to compression. The game can still be played partially from CDs, but loading times could be longer due to the need to decompress the .BIF files compared to the prior 6 CDs or the 1 DVD + 1 CD methods of playing Baldur's Gate with the Tales of the Sword Coast Expansion. A full hard drive installation will result in decompressed .BIF files being made available to the game. I understand this was the version gog.com was offering before the Enhanced Edition was released in 2012. I used to think this version was more prone to crashing than the versions with non-compressed .BIF files, but if anything crashes are only more likely to occur when decompressing .BIF files off the CDs.
1.0.430X - This mysterious version number has been encountered only twice to my knowledge. It can be found in the readme of the Japanese-translated release of the game and in the readme of an obscure DX7 multiplayer beta patch. The 1.0.430X readme has less text in it than the 1.0.4309 readme, suggesting it was a leftover of a near-final pre-release version whose readme somehow got included with much later files.
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