X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=dosdemo;a=blobdiff_plain;f=README.md;h=b3a41a1e2e394608b01c718de18a05340b331d35;hp=ec9721ffe1b7f3d968d3c3b318c81da521b9e704;hb=7cffbf057545fb303ad8f53e432ef42f7708e16d;hpb=68f89fa06ae5cfacde9cf8310e97220e5fc05260

diff --git a/README.md b/README.md
index ec9721f..b3a41a1 100644
--- a/README.md
+++ b/README.md
@@ -129,3 +129,21 @@ U-only pairable instructions:
  - adc, sbb
  - shr, sar, shl, sal with immediate
  - ror, rol, rcr, rcl with immediate=1
+
+Notes about DJGPP & CWSDPMI
+---------------------------
+Can't use the `hlt` instruction for waiting for interrupts, because we're
+running in ring3 by default. I surrounded all the `hlt` instructions with a
+`USE_HLT` conditional, which is undefined when building with DJGPP.
+
+It's possible to arrange for our code to run on ring0 by changing the DPMI
+provider from `cwsdpmi.exe` to `cwsdpr0.exe` by running:
+`stubedit demo.exe dpmi=cwsdpr0.exe`, but I haven't tested under win9x to see if
+it still works if we do that.
+
+Our fucking segments don't start at 0 ... to access arbitrary parts of physical
+memory we need to call `__djgpp_nearptr_enable()` and use the following macros I
+defined in `cdpmi.h`:
+
+    #define virt_to_phys(v)	((v) + __djgpp_base_address)
+    #define phys_to_virt(p)	((p) - __djgpp_base_address)