On Fri, 6 Dec 2002, S.Gopi wrote: > I want to use HIMEM.SYS under DOSEMU with FreeDOS. I heard that this is > not possible and I was advised to use XMS and EMS settings available > under DOSEmu. But I read from FAQs is that I cannot use them if my > program uses VCPI or some other method to access high memory access.
HIMEM.SYS services are *provided* by DOSEMU. HIMEM.SYS might be able to run in DOSEMU if DOSEMU would implement int 0x15/0x87 to copy extended memory though. However it's a fairly pointless exercise unless you really need some very special use. > I tried loading HIMEM.sys and it bounced back with error message > 'Unable to Control A20 Line', after some quick hack into dos code I > found that DOSEmu is explicitly disabling A20 line and denying any > further interrupt calls on that (i guess it is int15,0x87 and 0x88) a) dosemu does not implement int15/0x87 b) dosemu emulates A20 through these calls 1. XMS driver calls ah=3/4/5/6/7. 2. the relevant I/O port (keyboard related). using a paging technique. The XMS driver API (in real DOS this API is provided by HIMEM or FreeDOS FDXMS) has been in DOSEMU for ages. The port technique became necessary when we found out that Windows ME DOS bootdisks use that. > May i know why is it so? If DOSEmu can allow these interrupts then > programs like himem.sys can use of this and provide the memory manager > suppor with VCPI support etc. Is there any technical difficulty or > memory blocking issues with this or it is disabled for some anonymous > reasons. himem.sys might run, but VCPI support is out of the question without CPU emulation; VCPI needs ring-0 access. Bart - To unsubscribe from this list: send the line "unsubscribe linux-msdos" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
