Hello
Thanks Jim and Eric for your replies. On DOSEMU2, FreeDos's MEM command
reports 633K free on my Linux PC. Same for DRDOS's MEM command. 4DOS's
MEMORY command reports 648K free. For FreeDos under QEMU, the DRDOS MEM
command crashes, FreeDos's MEM command reports 612K free and the MEMORY
command reports 626K. DOSEMU2 runs about 4.5 to 6.5 times slower
compared to MS DOS 5 on an ancient XP PC (VDM). FreeDos 1.2 under Qemu
runs 5.6 to 8.6 times slower. 4DOS is present on all installations.
Available memory and speed have no impact on my applications.
The reason I have moved to DOSEMU2 is the ease of transferring files to
and from the DOS drive. As I previously alluded, my experience mounting
the QEMU DOS drive image and copying files, resulted in the original
file timestamps being replaced with the time of the copy. The file
timestamps are crucial for my application. (The way around this was to
copy files to the access drive (D:) and then use XCOPY to move them to
the C: drive - this taking 20 minutes or longer)
John
On 2025/03/09 18:11, Eric Auer via Freedos-user wrote:
Hi!
Apologies, please disregard my first question in my previous mail.
I did a second clean install of dosemu2 and had failed to edit the
fdppauto.sys file.
John
Dosemu2 defaults to using a special kernel and shell, partly
living in the Linux memory space of Dosemu2 afair. But when
you use classic FreeCOM and FreeDOS kernel, you will have
other config files active than in a default Dosemu2. You also
want to load some *Dosemu2 specific drivers* even if you are
going to use another DOS than the one bundled with Dosemu2.
In related news, ECM compared several DOS versions in Dosemu2:
https://retrocomputing.stackexchange.com/questions/31384/whats-the-86-dos-system-with-the-smallest-low-memory-area-footprint/
With MS DOS 5.0 and FreeCOM, you get 617 kB free for running apps.
With FreeDOS and FreeCOM as SHELLHIGH using UMB, you reach 628 kB.
FreeDOS also uses UMB "high" FILES, BUFFERS, LASTDRIVE and STACKS.
With the lDOS variant of EDR-DOS, you reach 632 kB and finally
with the lDOS variant of MS DOS 4, even 636 kB are possible, the
kernel based on Microsoft's MIT source release, modified by ECM.
Of course this is all a bit academic, because you can configure
Dosemu2 to give you unrealistically large amounts of UMB space
and HMA and the EMS and CDROM drivers only have small parts in
DOS memory space, the rest residing in Dosemu2 Linux land.
Now I wonder what the DOS apps with the largest amount of DOS
memory needed would need :-) Probably much less than 640 kB.
Cheers, Eric
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