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nc_mike
June 12th, 2016, 12:45 PM
I'm working on a 40MHz PC AT clone (a DTK DATA 1000), and it has 640K conventional RAM and 16MB of extended. It has no shadow RAM. I was down to around 480K after installing a lot of apps in DOS, so I thought I'd give 386MAX R7.2 a whirl to see what it could do. It did pretty well, freeing up enough to make about 590K or so available after loading a fairly packed system (it looks like it recovered some of the monochrome adapter area). One thing I didn't expect is that in Windows 3.1 on the same machine there are not 386MAX DOS icons for running either a DOS full screen session or a DOS windowed session. Each session shows 641K available for running DOS programs - nice! I was wondering two things 1) why is the total available ram 641K vs 640K? and 2) Where is getting the memory? Is it virtualizing the extended memory in those sessions?

Regards,
Mike

krebizfan
June 12th, 2016, 01:09 PM
That sounds about right. I think the extra free memory under Windows 3 enhanced mode is just 386MAX not loading as many EMS handles for a DOS session as it does with real mode DOS.

ftp://ftp.nars2000.org/support/max/ has some support text files. All the 386 EMM products have some tricky compatibility issues so forewarned is forearmed.

GiGaBiTe
June 12th, 2016, 02:05 PM
Each session shows 641K available for running DOS programs - nice! I was wondering two things 1) why is the total available ram 641K vs 640K? and 2) Where is getting the memory? Is it virtualizing the extended memory in those sessions?

Regards,
Mike

Microsoft introduced Virtual DOS Machines (VDMs) in Windows/386 2.01, which allowed real mode and most protected mode DOS programs to be virtualized. Since the DOS instance was virtual, Windows could emulate a full megabyte of conventional memory from EMS/XMS memory (assuming there was enough system memory available.) The amount of emulated conventional left over (in your case 641k) is because Windows is emulating all of the memory regions that would be present in a real DOS memory map (CGA, EGA, VGA, BIOS, etc.)

I've had FreeDOS get up to 736k of free conventional memory with no TSRs or drivers loaded, presumably it detects which regions of conventional memory aren't being used and reclaims them.

nc_mike
June 12th, 2016, 03:15 PM
Microsoft introduced Virtual DOS Machines (VDMs) in Windows/386 2.01, which allowed real mode and most protected mode DOS programs to be virtualized. Since the DOS instance was virtual, Windows could emulate a full megabyte of conventional memory from EMS/XMS memory (assuming there was enough system memory available.) The amount of emulated conventional left over (in your case 641k) is because Windows is emulating all of the memory regions that would be present in a real DOS memory map (CGA, EGA, VGA, BIOS, etc.)

I've had FreeDOS get up to 736k of free conventional memory with no TSRs or drivers loaded, presumably it detects which regions of conventional memory aren't being used and reclaims them.

Thanks for the good explanation!! So far I haven't experienced any instability with a few dozen DOS and Win apps - fingers crossed.

Mike

Shadow Lord
July 4th, 2016, 10:40 PM
That sounds about right. I think the extra free memory under Windows 3 enhanced mode is just 386MAX not loading as many EMS handles for a DOS session as it does with real mode DOS.

ftp://ftp.nars2000.org/support/max/ has some support text files. All the 386 EMM products have some tricky compatibility issues so forewarned is forearmed.

Is this site still up? I tried accessing it but didn't get far (i.e. the FTP site is running but no permission to list files or do anything...)

modem7
July 5th, 2016, 12:05 AM
Is this site still up? I tried accessing it but didn't get far (i.e. the FTP site is running but no permission to list files or do anything...)
No problem for me. I am able to click on various .txt files in the list and have the contents display. In case its is relevant, I am using Firefox.

Shadow Lord
July 5th, 2016, 12:23 AM
No problem for me. I am able to click on various .txt files in the list and have the contents display. In case its is relevant, I am using Firefox.


Okay weird. If I log in at the root level (ftp.nars2000.org) and then drill down the directory listing it works for me but if I try to go directly using ftp.nars2000.org/support/max it fails both on IE and CuteFTP. Thanks for letting me know it was up!