Hi again,

On Wed, Sep 5, 2012 at 5:50 AM, Rugxulo <rugx...@gmail.com> wrote:
>
> On Wed, Sep 5, 2012 at 2:14 AM, Felix Miata <mrma...@earthlink.net> wrote:
>>
>> Is FreeDOS HD access as slow as PC or MS DOS? IIUC, the latter use slow 16
>> bit BIOS code, which is what makes it painful for me to use compared to
>> running DOS apps in an OS/2 VM.
>
> Yes, probably just as slow as it also uses the BIOS.
>
>> Is FreeDOS disk I/O in the same class as 32 &
>> 64 bit operating systems speed-wise?
>
> No, FreeDOS is pure 16-bit, but with Ultra DMA enabled and a software
> cache (e.g. UIDE) can help a lot. That's about the best you can do
> outside of just running under DOSEMU or similar (NTVDM).
>
> BTW, things like DOSLFN slow down file accesses a lot, so avoid them
> if possible.

Just for the record, I don't know why it's faster under DOSEMU (or
similar), probably just because the file system is slightly more
efficient or multithreaded, dunno. Or maybe these new-fangled
computers are just slow at old 16-bit code (probably). But honestly,
faster than even DOSEMU is to just use a cross compiler (which I
really hate to admit because I prefer native building). "make -j4"
atop Linux will definitely run faster than under native FreeDOS (which
can't multitask).

Anyways, here's a concrete example:   building p7zip 9.20.1 (7za.exe
only) via G++ 4.7.1 (DJGPP 2.04 host and target) on this particular
machine:

(N.B. p7zip doesn't really build under 8.3 SFNs without some fairly
minor source patching. I did upload the changes, but I doubt most
people care. Somewhat tedious and painstaking to solve that but
nothing too too bad. Anyways ....)

1). native FreeDOS, no LFNs, XMGR + UIDE, built atop RDISK, HDPMI32 -r
2). native FreeDOS, same as above but with DOSLFN loaded
3). DOSEMU + FreeDOS (with its own LFNs, XMS, DPMI, etc.) atop Lucid
PuppyLinux 5.18

1). (SFN) Elapsed time: 354.050 seconds (0:05:54.050)
2). (LFN) Elapsed time: 430.840 seconds (0:07:10.840)
3). (EMU) Elapsed time: 303.190 seconds (0:05:03.190)

So, for the record, fastest to slowest is DOSEMU, native FreeDOS, and
LFN-enabled FreeDOS. But we're only talking 5 vs 6 vs 7 mins. here,
indeed quite noticeable here but nothing too horribly different.

--
"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

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