Feedback needed on BOOTING, CACHING and some HELPER TOOL

Hi, in reply to: Re: MetaKern / ... suggestions revisited
(from Bart), I have some questions.

Bart writes that the BIOS only calls the boot sector or MBR with DL set to
either 0 or 0x80 (A: or C:). I wonder what happens with modern BIOSes that
allow booting from D: ? Do they change the order of drives, so that 0x80 and
0x81 get swapped? Bart also writes that autoexec.bat is only read from A:
or C: when boot drive is "any floppy" or "any harddisk" (at least for hard-
disks, this is very useful, because one cannot know which drive letter the
"currently active partition of drive 0x81" and so on corresponds to normally,
especially when boot managers are involved). Also, he writes that the MBR
may set the drive number to an arbitrary value before starting the boot
sector. I think for FreeDOS this means you can load the KERNEL from any
drive, but the autoexec.bat / config.sys issue remains (you know, config.sys
can point to autoexec.bat at arbitrary position using /P=x:\foo\bar.bat or so).

Bart also reminded me that FreeDOS -does- have a "prompt for path to the
command.com" which gets active when the shell is not found or exits un-
expectedly. I was accidentally requesting the feature again :-). MS DOS
has this as well. You can enter any program that can stand not having a
parent process as your new shell at that kernel prompt, I would say.

Finally, if some of you still have SMARTDRV: Yes, I know, most of the
performance comes from the ability to pool/delay writes. But could you
please benchmark two other things for me?
- smartdrv defaults to an element size of 8k (1..8k possible), even though
  this increases the resident size. I am planning to change the element
  size of LBAcache from 2k to 4k, which will actually DECREASE the amount
  of DOS memory used :-). The problem is that an element size which is
  smaller than the cluster size could decrease performance, I believe. The
  reason is that all sectors in a cache element must be from the same region
  of the disk, so the cache gets less flexible in chosing which sectors to
  cache with bigger element sizes. Please tell me what happens with different
  element sizes for SMARTDRV (please disable write caching with the /X option)
  for your favourite benchmark application.

- Smartdrv allows the use of a read-ahead buffer. SMARTDRV reads by default
  16k more when you do large reads, in anticipation of successive reads. You
  can give other sizes with the /B:size option (must be a multiple of element
  size), for example 0. Adding read-ahead to LBAcache would mean - like with
  SMARTDRV - an extra buffer in DOS memory to be required. In SMARTDRV, the
  buffer is as big as the read-ahead, but with LBAcache, it could be as small
  as 1/2k. Please tell me if read-ahead is worth the effort after doing tests
  with your favourite benchmark application (yet again with /X. Try e.g. values
  of /B:0, the default 16k and /B:64k - not sure about the "64k" syntax here
  but you get my point).


Finally, I would need some special extra for batch file processing:
something like "dir > @foo" which would store the output of dir in the
environment variable FOO would be nice. However, I currently only need
one SIMILAR tool:

thingy x:\foo\bar\baz.com

would set %DRV% to X (preferably not X:), %DIR% to \foo\bar (or \foo\bar\)
and %NAME% to baz and %EXT% to com (preferably not .com).

cd | thingy

would set %DRV% and %DIR% (would need to detect that "bar" is a directory
and not a file, because "cd" does not print the trailing "\").

echo x:\%DEST%\file%NUMBER%.com | thingy

would set %DRV% and %DIR% and %NAME% and %EXT% in a way which you already
guess by now :-). A bonus option could allow:

echo x:\%DEST%\file*.com | thingy /new

which would fill the "*" area in a way that makes the resulting file
name the name of a not yet existing file, for example by filling in a
number.

Do you know such a tool? Or do you feel like writing one? I think it would
not be too hard. Thanks for your efforts!
Feel free to virtually kick me to force me writing that tool myself...

Cheers, Eric


PS: Bart usually uses Dosemu to compare kernels. Anybody else that could
need a "prompt for KERNEL name" feature in MetaKern? Anybody that could
use some "boot from B:" or "D:" menu entries there (see discussion above)?

I think the only useful addition to the current version would be a "boot
from A:" menu entry. Comments?

PPS: SMARTDRV is part of MS DOS and incompatible to most of our memory
drivers, so please test it with MS DOS. At your option, use the DR-DOS
cache to do similar tests as the suggested ones above. All other mentioned
software like LBAcache and the MetaKern boot menu can be found either at
http://www.coli.uni-sb.de/~eric/stuff/soft/ somewhere or at some other
place in the FreeDOS universe :-). The "thingy" cannot be found anywhere yet.