DOS ain't dead

DOS copy command (Developers)

posted by ecm  , Düsseldorf, Germany, 28.09.2010, 01:16
(edited by cm on 28.09.2010, 01:27)

> Also, according to MS-DOS 6.2 HELP, you can give BUFFERS two different
> numbers:
>
> BUFFERS=n[,m]
>
> where m is the size of the secondary cache. Does anybody have any idea how
> MS-DOS uses a two-stage cache? HELP doesn't really explain it, but
> indirectly refers to the secondary buffer cache in the context of SMARTDRV
> (and possibly double-buffering?).

I've seen sites that state the "secondary cache" is only useful for 8086 CPUs - however, that might be related to SMARTDRV (is it unable to run on 8086?). It is apparently recommended to leave the "secondary cache" unused if SMARTDRV (or another cache) is used. Apparently the setting is limited to 0..8, or at least that's what some sites say.

I vaguely remember it to be some kind of look-ahead cache, but I don't remember where I read that and didn't find any source supporting that claim right now. So that might be wrong.

EDIT: Also here's some stuff Eric sent us per mail for whatever reason:

> Hi, a comment on the dos copy command threat: Try first setting
> the file to the right size (seek to end-1, write a byte, close)
> and then reopen the file and start writing data, for example in
> 32k blocks, taking care that the 32k buffer does not wrap around
> a multiple of 64k in terms of linear address / DMA boundary. The
> idea is that setting the final size immediately avoids having to
> update the FAT again later: The file size does not change later,
> while it would change all the time if starting with an empty file
> and appending data to it until all content is there...
>
> Eric

Good call, at least setting the size initially. Does COPY do this? It should. (What about FreeCOM's COPY, and FD's XCOPY?)

EDIT:

Ah well Bret. Try this (search for "secondary cache"). Though I'd guess Richard doesn't know more than that either.

---
l

Complete thread:

• DOS copy command - georgpotthast, 26.09.2010, 21:37 (Developers)
  • DOS copy command - ecm, 26.09.2010, 23:46
  • DOS copy command - Japheth, 27.09.2010, 02:06
  • DOS copy command - georgpotthast, 27.09.2010, 21:28
    • DOS copy command - ecm, 27.09.2010, 21:40
      • DOS copy command - georgpotthast, 27.09.2010, 22:46
        • DOS copy command - bretjohn, 28.09.2010, 00:15
          • DOS copy command - ecm, 28.09.2010, 01:16
            • DOS copy command - Rugxulo, 28.09.2010, 05:37
            • DOS copy command - Rugxulo, 28.09.2010, 22:40
              • DOS copy command - Rugxulo, 30.09.2010, 06:51
                • DOS copy command - georgpotthast, 30.09.2010, 19:59
                  • DOS copy command - tom, 01.10.2010, 15:12
                    • DOS copy command - georgpotthast, 02.10.2010, 22:56
                      • DOS copy command - RayeR, 08.10.2010, 10:10
            • DOS copy command - nidud, 03.10.2010, 17:17
          • DOS copy command - georgpotthast, 28.09.2010, 21:04
            • DOS copy command - ecm, 29.09.2010, 14:05
  • DOS copy command | FATPLUS.EXE - DOS386, 13.10.2010, 04:02