I want to learn how I can access more than 1 MB of memory using EMS. Can someone teach me? I don't understand about it.

Do you really want to use hardware EMS on 8086 ???

In any other case, use XMS (RTFS: see FASM source), or brew a 32-bit DOS app (see FAQ on the top and examples).

I want the fastest. EMS, XMS, a 32-bit protected mode program or DPMI (like FASM)?

Uau,entende isso?

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What's the better? XMS, EMS, Protected Mode or DPMI?
"Obrigado"

The fastest would be 32bit (or 64bit) ring0 code with manual memory management... but that's only viable if you do bare-metal programming.

IMHO just go for a DOS extender and use it's API - you're unlikely to see much of a speed difference anyway, and the DOS extender can select between ring0+manual, DPMI/VCPI client, whatever

So, how to use DPMI? (The simplest way)

HX - http://www.japheth.de/

Thinking better: how to use EMS or XMS on DOS or Windows?

Unreal mode is better.

Care to substantiate that?

Easier.

see FASM source old version (dos)

Dunno if it's easier - rolling your own is some work, and if you're going to use somebody else's, you might as well use a full-blown extender, unless you have very specific reasons not to (learning project, 4k intro, ...).

Also, unreal/voodoo/big real/etc only works when run from real-mode, right? And only supports running your code from base memory, right? Using a DOS extender, you'll be able to handle a loaded EMS driver (through VCPI), to run under Windows and some other OSes (DPMI), from real mode, etc...

OK, so it's slightly more work calling DOS functions, but decent DOS extenders either translate the most common interrupt calls or offer a lightweight Win32 API translation layer.

But OK, if you're writing SMM code, it's probably not the worst mode to use

Anyway, A$M: what's your goal? Accessing extended memory under DOS in a convenient way, or do something quirky to learn from the process?

I written a true Dos extender, that runs on top of any Dos, that let you use all int 21h in PM giving you full 4 GB memory, it also lets you drop back to normal dos at any time.
Its got a fasm port and both cli and gui
The int 21h are the same as dos other than they use 32bit regs.



Let me know if you want to try it.
Plus its only 55k in size.

> So, how to use DPMI? (The simplest way)

Again, RTFF

PS: ???

> Thinking better: how to use EMS or XMS on DOS or Windows?

Thinking worse. Don't use EMS or XMS on Windows, learn WinAPI then.

Options:

* Brew your own non-DPMI Ring0 DOS extender (fastest, much work)
* Use an existing DOS extender (simplest, works in DOS)
* Brew a Win32 app working in both DOS (using HX) and Windows
* (bad) Brew a Win64 GUI app using latest API's ... not usable in DOS

Depends what you really need and what are you looking for. First of all some BIOSes and HIMEM.SYS leaves your system in unreal mode so on some configuration it's on by default but you still need to take care of cases when switching 3rd party applications are switching into PM so you need to have 0Dh INT handler to handle this properly. Within the handler you need to read PIC registers for checking if IRQ5 is not a true source of interrupt or you need to remap IRQ.

The biggest drawback of big flat mode / unreal mode are:
- forget about multitasking and especially running under Windows
- many DOS configuration are running in V86 mode due to memory manager

So unless you really need it PM DOS Extender that supports DPMI, VCPI and is DPMI host is the way to go in my opinion. Especially if you plan to use some multitasking environment. HX is a way to go with PharLap TNT extender second.

> The biggest drawback of big flat mode / unreal mode are:
> - forget about multitasking and especially running under Windows

It's a feature

> many DOS configuration are running in V86 mode due to memory manager

Don't use EMM386.

Speaking of which, do you know of any x64 DOS extenders? Personally don't see much use for it (and I guess at that complexity level, you're probably better off using some minimal OS kernel instead).

ACP: exactly - and when you need to do that extra work, unreal mode isn't that simple anymore... and still has a somewhat fragile feel to it. Btw, why PharLap as a second? Never used it, back then I thought DOS4G/W was king? And later, we got the free WDOSX extender?


Got an alternative for people who run applications that need EMS memory?