Hi, On Sat, Jul 2, 2016 at 2:19 PM, Abe Mishler <a...@mishlerlabs.com> wrote: > > I'm interested in learning how games like DOOM (requires 3MB available) > were able to work. I know I know, read the source code.
AFAIK, Doom was originally compiled with Watcom using a DOS extender (DOS4G Professional). So it's 386 pmode code. All the open source ports (since late 1997?) started with the so-called Linux sources (thus no DOS soundcard support), so pretty much all of the newer DOS-based ports used DJGPP v2 (DPMI) and Allegro (sound, gfx). This was before OpenWatcom was officially released (2003). See here: ftp://ftp.idsoftware.com/idstuff/source/doomsrc.txt > I'm getting there. I'm also reading "MS-DOS Beyond 640K" by James Forney. > Interesting to note that Id says not to use memory managers or disk caching > programs with Doom. Even back in the DOS days, I don't think anyone was naive enough to expect everyone to (always) run without any memory managers. DOS extenders usually went out of their way to support multiple environments (raw, EMS/VCPI, XMS, DPMI). Certainly running under Windows wasn't always forbidden, and that won't let you disable everything. Yes, some DOS games needed a fairly clean setup, but most of them (by design) could handle themselves gracefully in multiple environments. E.g. Quake (DJGPP-based) was explicitly debugged and tested so that it could run under Win95 with (I think?) only 16 MB of RAM. > Doom and other games must do their own memory management which makes sense > for performance. Doom may allocate everything up front and privately manage it all itself, but that's all. It's not overriding the OS (or APIs). And yes, that was probably faster for 1993, back when the best you had was a fast 386 or slow 486. Although technically the Intel Pentium (586) first came out in 1993, but it wasn't common. Even when Quake came out in 1996 (and was heavily optimized for Intel's pipelined 587 FPU), the Pentium wasn't universal. ------------------------------------------------------------------------------ Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San Francisco, CA to explore cutting-edge tech and listen to tech luminaries present their vision of the future. This family event has something for everyone, including kids. Get more information and register today. http://sdm.link/attshape _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
