DOS ain't dead

Jwasm 2.0 and 64 bit real mode (Announce)

posted by Japheth , Germany (South), 13.10.2009, 11:08

> Hello Japheth and all,
> I see that that jwasm 2.0 production release was posted today on
> http://www.japheth.de/

Yes. Changes:

- support for 64-bit enabled.
- directives for 64-bit SEH added (.ALLOCSTACK, .PUSHFRAME, ... )
- directive .SAFESEH and cmdline option -safeseh supported.
- cmdline option -Zd implemented for COFF output format.
- cmdline option -Zi implemented for OMF and COFF output formats.
- operators IMAGEREL and SECTIONREL work with BIN format, which makes it
possible to create PE binaries using this format.
- ELF32 format: LD extensions for 8/16-bit relocations supported.

See http://www.japheth.de/JWasm.html for more.

> I read the "64bit DOS sample" comments on this forum & my question is
> this: What can be done with this mode?
> You call it 64bit real mode, what memory limitations does it have?

No, it isn't "64bit real mode", it's the normal 64bit long-mode. There are no memory limitations in this mode.

> Using the sample code "Dos64.asm" as a model, would it be possible to
> write DOS programs/device drivers/command processors that uses this mode?

You can probably write a few useful programs using this sample as a template, but without a possibility to access DOS or BIOS functions it's rather limited.

> Could a 64bit Real Mode DOS be written that would be backwards compatable
> with 16bit DOS?

No. But it's possible to write a 64-bit DOS extender which runs application in 64-bit long mode.

However, as far as access to more than 4 GB is concerned: unlike to what Rugxulo babbles it's pretty likely that a small extension will be implemented in JemmEx ( and maybe also in J.R. Ellis' XMGR ) which supports more that 4 GB of memory. It is likely because it's not much work and the main reason why it isn't done yet for JemmEx is because I don't have access to such a machine yet. The extension will implement 4 MB pages. IIRC it's possible to access up to 1 TB (40-bit addresses) of physical memory with 4 MB pages.

---
MS-DOS forever!

Complete thread:

• Jwasm 2.0 and 64 bit real mode - swf, 12.10.2009, 22:49 (Announce)
  • Jwasm 2.0 and 64 bit real mode - Rugxulo, 13.10.2009, 02:31
  • Jwasm 2.0 and 64 bit real mode - Japheth, 13.10.2009, 11:08
    • Jwasm 2.0 and 64 bit real mode - Jack, 13.10.2009, 20:32
    • Jwasm 2.0 and 64 bit real mode - RayeR, 14.10.2009, 00:36
      • Jwasm 2.0 and 64 bit real mode - Japheth, 14.10.2009, 06:08
        • Jwasm 2.0 and 64 bit real mode - RayeR, 14.10.2009, 13:18
          • Jwasm 2.0 and 64 bit real mode - ecm, 14.10.2009, 14:14
            • Jwasm 2.0 and 64 bit real mode - Rugxulo, 19.10.2009, 10:44
      • Jwasm 2.0 and 64 bit real mode - Jack, 14.10.2009, 10:34
        • Jwasm 2.0 and 64 bit real mode - RayeR, 14.10.2009, 13:41
        • Jwasm 2.0 and 64 bit real mode - swf, 14.10.2009, 16:01
          • "Extended" Memory With XMGR. - Jack, 14.10.2009, 19:51
            • "Extended" Memory With XMGR. - swf, 15.10.2009, 18:57
              • "Extended" Memory With XMGR. - Jack, 15.10.2009, 19:42
        • Jwasm 2.0 and 64 bit real mode - Zyzzle, 15.10.2009, 07:35
          • Over 4-GB For UIDE/RDISK. - Jack, 15.10.2009, 09:19