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RDRVSX32: FAT32 RAM drive for HimemSX (Announce)

posted by Richard, 17.03.2022, 05:04

> > @Jason
> >
> > My results so far
> >
> >
> > [image]
> >
> >
> >
> >
> >
> https://www.dropbox.com/s/s3ro7z074lkqia0/FAT32_28G.png?dl=1
>
> Very interesting.
>
> How did you create / copy those 4095 MiB files on the ramdrive in DOS? The
> best I can do is 2047 MiB since my DOS (MS-DOS 7.1) doesn't support
> unsigned long integer seek / create. Which DOS are you using? How did you
> get it to support long unsigned file seeks? I assume you're on bare metal
> DOS?
>
> It appears that you have 32 GiB total system RAM and the the new Ramdrive
> has problems with accessing beyond 24 (?) GiB.


I created a USB BOOT stick using Rufus with the image file from FreeDOS RC5 (full usb image). Note RC5 has just recently been replaced with FreeDOS 1.3. As per guidelines from FreeDOS two partitions on the USB stick were created (the C:\ partition is only 512 Mbyte total (of which ~~400 MByte is used by FreeDOS).

I used the FreeDOS default FDCONFIG.SYS and FDAUTO.BAT as the framework for my configuration (and did some adjustments to suit my needs).

So with the laptop BIOS setup for "Legacy Mode", I boot up from the USB stick and the USB stick is C:\, D:\, E:\ drives of capacity 512 MB, 12 GB, 2 GB respectively (for my 16 GB USB stick). The hard drive of my laptop is not "visible" to the FreeDOS environment. Also (still having to sort things out), drive F:\ is the built-in DVD drive. So to answer your question - YES, working in bear metal mode (no virtual machine (VM) stuff at all).

The laptop has 32 GByte RAM (which is the maximum allowed for the INTEL i7 4th generation 4810MQ processor). Note that my laptop has a Q3 display (3200 x 1800) and because of this, I think that a big "chunk" of XMS (i.e. the first 4 GB of standard Extended Memory) is reserved for the display. When actually running FreeDOS the whole display area is used, so it seems a waste of display resolution for a DOS text based display (but this is what I have).

So the first 4 GB is XMS, the remaining 32-4 = 28 GB is SXMS. I set up a ~1.4 GB FAT32 G:\ RAMdrive in XMS, and ~28 GB FAT32 H:\ RAMdrive in SXMS. I think that the supplied digital photograph screenshot clearly indicates this. I used both WhichFAT.com and trace.com to verify the FAT size. I think that if you do the sums of bytes used + bytes free, for H:\, the result is 28 Gbyte. Now g:\ is only ~1.4 GB (in XMS), and this value is about the maximum, it seems, I can have for G:\. So I have "problems accessing all of the XMS", i.e. the first 4 GB of memory (keep in mind that maybe my Q3 display is a significant factor here).

So to sum up, 1.4 GB (G:\) + 28 GB (H:\) ~= 29.4 GB RAMdrives (total) as FAT32 appears to have been achieved. I don't know if I can "squeeze" out any more memory as RAMdrive.


As to the question of DOS version used - I don't know - it is whatever is the default settings of FreeDOS RC5 (or if you wish 1.3 official release).

Via a simple BASIC program (in windows 10), I created a 1 GByte file (1024 * 1024 *1024 bytes), the filename is "1", and copied it to my USB stick to the appropriate partition (D:\ when in bare metal metal). So the relevant lines in FDauto.bat are


copy d:\1 g:\1
copy g:\1 h:\1
copy h:\1 + h:\1 + h:\1 + h:\1 h:\4
copy h:\4 + h:\4 h:\8
copy h:\4 h:\4a
copy h:\4 h:\4b
copy h:\4 h:\4c
copy h:\4 h:\4d
copy h:\4 h:\4e

so the 1 GByte file, filename "1", on the USB stick D:\ partition, is copied to the FAT32 drive G:\ (in XMS), and this copied file is copied to the FAT32 H:\ (in SXMS). I used the old method of adding two files together (here they are plain ascii files) to generate a 4 GB file "4". However, as expected, if I try to create a 8 GB file "8"- only a 1 byte file is created.


This reply to you is very verbose - but I hope it answers all your questions.

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