China DOS Union

Good post

Not bad! Support!

Looks like Master Rushi has really studied DOS in depth.

Let’s continue talking about memory. How do we get more conventional memory under DOS? As mentioned earlier, most programs in a DOS environment run in conventional memory. If a certain program fails to run because of insufficient memory, the most common problem is a lack of conventional memory. So today we’ll introduce several ways to free as much conventional memory as possible:
1. When the system is configured with extended memory, most of DOS and the resident portion of Command.com can be installed in the High Memory Area (HMA). This requires the following commands in config.sys: 　　　　　　
　　device=Himem.sys
　　dos=high

　　Although Himem.sys itself also occupies a small amount of conventional memory, using HMA will save us more conventional memory overall. Also, in versions above msdos7, we can use devicehigh=himem.sys to place Himem.sys in upper memory. We have already discussed the special dos command in the config file earlier. Here I’ll just briefly talk about Himem.sys.
Himem.sys manages the use of expanded memory and the High Memory Area (HMA). This device driver is configured in the config file through the device command. If we use expanded memory and high memory, then the device command installing Himem.sys must come before the installation of any other driver.
Its general command format is:
device＝Himem.sys /options
Options:
hmamin＝an integer from 0 to 63, default value 0
This option specifies the amount of conventional memory DOS must use before Himem.sys uses HMA (the high memory area). The unit is KB.
numhandles＝an integer from 1 to 128, default value 32
This option specifies the maximum number of EMB (expanded memory block) handles DOS can use simultaneously. Each handle occupies 6 bytes of conventional memory.
int15＝an integer from 64 to 65535, default value 0
This option specifies the amount of expanded memory allocated by interrupt 15h. To ensure enough memory is available, this value must be greater than 64.
machine: code corresponding to the A20 handler. (I’m not very clear on this option either)
The A20 handler is probably a kind of microcomputer component that can access the high memory area...
a20 control: on/off
This option specifies whether Himem.sys obtains control of the A20 handler. The default value is on.
shadowram: on/off
This option specifies whether Himem.sys disables the RAM portion of ROM (read-only memory).
cpuclock: on/off
This option is used to specify whether Himem.sys affects the clock speed of the CPU....
DOS only allows one program to use the high memory area at the same time. If we do not specify /hmamin＝xxx, then Himem.sys reserves HMA for the first program that needs it..

DOS really is broad and profound! It’s a bit hard to learn.

This is pretty good.

I forgot where I saw this, let me add a bit more! It was from some software called Learning Memory, seems a bit old! But just treat it as reference material!
RAM is memory in the conventional sense, the kind we use now!
To put it plainly, ROM is a block of memory used by the BIOS that can be erased and written by special methods!
It also talked about real mode, protected mode, and V86 mode here, as well as their addressing methods! I’m not going to type all that out, if you’re curious, go find materials and read them yourselves!
0~~640 is called main memory or conventional memory!
640~~1024 is called upper memory!
Above 1024 is called extended memory!
1024~~1088 is called high memory!

Conventional memory!
When DOS boots, it occupies about 56K of memory! The other 579K is for user use! Of course we can use other software to use memory greater than 640K! Otherwise how would my current dual-channel DDR fit in here!
Upper memory
This area is reserved for BIOS and hardware interfaces! This 384K memory is attached to the video ROM and video RAM on the graphics card, as well as some controller cards?! Applications cannot directly access data in this area! This is why computers have the 640K memory limitation! Applications can only use conventional memory! Also: 160K of upper memory is unused! A monochrome display can use even more (>160K), and it can be used through a manager! This place is what Master Rushi called (upper memory blocks)
abbreviated UMB! It is memory usable on machines from the 80386 onward!
Extended memory
Located above 2 to the 20th power, beyond the 8086 addressing range, so it can only be used on machines after the 80286!
Since DOS can only manage 640K of memory, this area can only be indirectly managed through an extended memory manager conforming to the XMS specification!
XMS is an extended memory manager standard jointly drafted by intel; louts; ms; ast4. It defines the standard interface for determining memory access to extended memory, HMA, and upper memory, with the goal of avoiding conflicts caused by programs randomly accessing this area! himem.sys and emm386.exe both conform!… In other words, we can only use software like this to manage extended memory!
(Typing is exhausting! I originally thought there wasn’t much, but after checking just now! I still have 15 pages of my handwritten notes to type out! I’ll take a break and come back to do it! There’s too much included! I wonder if it’s useful!? Moderators, please take a look! If it’s not useful, then I won’t bother doing it! )

Default value
What is it?

Its general command format is:
FILES＝(an integer between 8 and 255), its default value is 8
FCBS＝(an integer between 1 and 255), (an integer between 0 and 255), default values are 40, 0
(For FCBS＝) the number before must be greater than the number after.
The number before must be greater than the number after.
I don’t understand.

Default value means the setting DOS uses automatically for the corresponding item when you do not set the above statement in the config file. It is done automatically by DOS.

Hehe~~ okay, I’ll absorb it slowly. Is there more?

Yes, yes, more is coming right away..

The following is quoted from Master Rushi on 2003-6-7 14:59:00:
Baizi asked about DOS memory. Generally, DOS memory is closely related to the config file. So I’ll talk about it here........

The moderator is just too good

Why is it that when I open my msconfig.sys I can’t see anything at all?
The contents are as follows:
rem
rem *** DO NOT EDIT THIS FILE! ***
rem
rem This file was created by the System Configuration Utility as
rem a placeholder for your CONFIG.SYS. Your actual CONFIG.SYS
rem file has been saved under the name CONFIG.TSH.
rem
Question for the experts!