dmccunney schreef op 8-1-2014 12:43:

> I did not miss his point.  I suggested a technique he could use to
> soak up *some* of his system memory.  I'm quite aware DOS and DOS apps
> can't use *all* of it, and that 4GB is the most he can use..

DOS drivers work within a single 4GB memory section, and lots of stuff 
gets taken out of it by memory-mapped hardware. For example my current 
machine only seems to find 1506MB in DOS and ReactOS. Perhaps system 
memory for integrated graphics takes away quite a bit of the 1st 4GB area.

With DOS drivers out of the question, you're left with bootloaders that 
can work above 4GB. Syslinux's MEMDISK can load disk images, but only 
below 4GB. a modified (by Chenall) GRUB bootloader can load disk images 
above 4GB. It would require a contiguous 4GB memory area somewhere in 
the above-4GB memory. Also coming into play is the disk image itself, as 
on disk it's only allowed to be 4GB due to FAT32 filesystem limitations. 
Perhaps decompression works, loading a compressed 20GB harddisk image 
into system memory.

Loading speed can be troublesome if BIOS is involved rather than some 
native full-speed accelerated mechanism. I've succesfully loaded the 
entire KNOPPIX (Linux) DVD (4GB size) to system memory by typing
"KNOPPIX 64 toram". Still not sure I could eject/remove the physical 
load device though or if it's still expected to be present.

> I have a 2GB partition allocated to FreeDOS on the machine where it
> lives, and I'm not coming close to using all of it.  I could put the
> entire FreeDOS drive on a ramdisk if the machine had that much ram to
> spare.

I don't know what to fill up DOS systems with either, not using them 
exclusively enough I'm afraid.

Bernd

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