DOS ain't dead

comment on flushing predecode queue (pre-Pentium) (DOSX)

posted by Japheth , Germany (South), 23.04.2008, 21:04

> Hey! This is not a theory, it's one of the few things consistently and
> correctly documented in Intel manuals; and it's not just the 386, the 486
> as well needs it - I used to have the printed Intel manual.

I have several working 486 which don't need it...

> Mind you, I'm
> not sure whether it even is not still officially recommended, or required,
> for some later processors (not just Intel's).

No. Pentium and above will always "serialize" certain opcodes, including moves to control registers.

> When doing a mode switch, in
> general you'll need both : a near jump (to flush the queue) and a far
> transfer (to fully load CS and its attributes). Of course, in this
> particular piece of code, you don't want the far jump, since you're only
> setting up "big real" mode, but you need the short jmp.
>
> I'm really surprised you are not aware of this point, considering the
> depth of your experience.

I AM aware of this, indeed, I had some rather longish discussions with someone calling himself Eric (Auer) about this topic. Amazing how one can waste time about a piece of code approc. 6 lines long ...

---
MS-DOS forever!

Complete thread:

• comment on flushing predecode queue (pre-Pentium) - Ninho, 23.04.2008, 10:06 (DOSX)
  • comment on flushing predecode queue (pre-Pentium) - Japheth, 23.04.2008, 19:54
    • comment on flushing predecode queue (pre-Pentium) - Ninho, 23.04.2008, 20:22
      • comment on flushing predecode queue (pre-Pentium) - Japheth, 23.04.2008, 21:04
        • comment on flushing predecode queue (pre-Pentium) - Ninho, 23.04.2008, 23:32
          • comment on flushing predecode queue (pre-Pentium) - Rugxulo, 24.04.2008, 19:18
            • comment on flushing predecode queue (pre-Pentium) - RayeR, 24.04.2008, 22:34
              • comment on flushing predecode queue (pre-Pentium) - Ninho, 25.04.2008, 08:11
                • comment on flushing predecode queue (pre-Pentium) - Japheth, 25.04.2008, 08:58
                  • comment on flushing predecode queue (pre-Pentium) - Ninho, 25.04.2008, 09:23
                    • comment on flushing predecode queue (pre-Pentium) - Japheth, 25.04.2008, 09:31
                      • comment on flushing predecode queue (pre-Pentium) - Ninho, 25.04.2008, 09:52
                        • comment on flushing predecode queue (pre-Pentium) - rr, 25.04.2008, 10:00
                          • comment on flushing predecode queue (pre-Pentium) - Ninho, 25.04.2008, 10:09
                          • comment on flushing predecode queue (pre-Pentium) - Steve, 25.04.2008, 11:05
                        • comment on flushing predecode queue (pre-Pentium) - Steve, 25.04.2008, 11:04
                          • comment on flushing predecode queue (pre-Pentium) - rr, 25.04.2008, 11:11
                            • comment on flushing predecode queue (pre-Pentium) - Japheth, 25.04.2008, 11:18
                              • comment on flushing predecode queue (pre-Pentium) - rr, 25.04.2008, 11:21
                                • comment on flushing predecode queue (pre-Pentium) - Japheth, 25.04.2008, 11:24
                                  • comment on flushing predecode queue (pre-Pentium) - rr, 25.04.2008, 11:41
                                    • comment on flushing predecode queue (pre-Pentium) - Japheth, 25.04.2008, 13:57
                                      • comment on flushing predecode queue (pre-Pentium) - rr, 25.04.2008, 14:34
                            • comment on flushing predecode queue (pre-Pentium) - Ninho, 25.04.2008, 11:34
                              • comment on flushing predecode queue (pre-Pentium) - Steve, 25.04.2008, 11:55
                                • comment on flushing predecode queue (pre-Pentium) - Ninho, 25.04.2008, 13:09
                                  • comment on flushing predecode queue (pre-Pentium) - Steve, 25.04.2008, 14:18
                      • comment on flushing predecode queue (pre-Pentium) - Rugxulo, 25.04.2008, 20:55
                • comment on flushing predecode queue (pre-Pentium) - RayeR, 26.04.2008, 00:54
                  • comment on flushing predecode queue (pre-Pentium) - Japheth, 26.04.2008, 09:49
                    • comment on flushing predecode queue (pre-Pentium) - Ninho, 26.04.2008, 10:29
                      • comment on flushing predecode queue (pre-Pentium) - Rugxulo, 26.04.2008, 20:57
                    • comment on flushing predecode queue (pre-Pentium) - RayeR, 27.04.2008, 01:52
                      • comment on flushing predecode queue (pre-Pentium) - Rugxulo, 27.04.2008, 05:36
                        • comment on flushing predecode queue (pre-Pentium) - RayeR, 27.04.2008, 13:20
                          • comment on flushing predecode queue (pre-Pentium) - Rugxulo, 27.04.2008, 20:20
                            • comment on flushing predecode queue (pre-Pentium) - flox, 27.04.2008, 22:08
                              • comment on flushing predecode queue (pre-Pentium) - Steve, 28.04.2008, 02:44
                        • comment on flushing predecode queue (pre-Pentium) - marcov, 27.04.2008, 15:46
                      • comment on flushing predecode queue (pre-Pentium) - Ninho, 27.04.2008, 10:10
                        • comment on flushing predecode queue (pre-Pentium) - Japheth, 28.04.2008, 11:50
                    • comment on flushing predecode queue (pre-Pentium) - tom, 27.04.2008, 14:46
                    • HIMEMX bug - DOS386, 01.05.2008, 05:48
                      • HIMEMX bug - Japheth, 01.05.2008, 09:20