Video ram size and system ram size 
Author Message
 Video ram size and system ram size

How to get Video ram size and system ram size ? I need to knwo this. Please
help me this. Thank you.



Sun, 03 Sep 2000 03:00:00 GMT  
 Video ram size and system ram size

Quote:

>How to get Video ram size and system ram size ? I need to knwo this. Please
>help me this. Thank you.

For the video RAM size you could use the VESA info block. For the system RAM you
could use the XMS size and add 1 MB.




Mon, 04 Sep 2000 03:00:00 GMT  
 Video ram size and system ram size


Quote:
> For the system RAM you could use the XMS size and add 1 MB.

Yes and no; the value will be wrong if the system has more than
64 Mb; the best is to program a small tool in pmode that will check
the effective available ram;
I also saw on some systems that the RAM that is at A000-FFFF is
sometimes 'moved' to the end of the physical memory, which was not
detected by XMS, but by my program; so sometimes more memory than
the one given by XMS is available (and usable of course !).

HTH,
Cedric
--
***************************************************************

* Antenna engineer - Alcatel Espace - Toulouse - France       *
***************************************************************



Tue, 05 Sep 2000 03:00:00 GMT  
 Video ram size and system ram size



Quote:

> > For the system RAM you could use the XMS size and add 1 MB.

> Yes and no; the value will be wrong if the system has more than
> 64 Mb; the best is to program a small tool in pmode that will check
> the effective available ram;
> I also saw on some systems that the RAM that is at A000-FFFF is
> sometimes 'moved' to the end of the physical memory, which was not
> detected by XMS, but by my program; so sometimes more memory than
> the one given by XMS is available (and usable of course !).

> HTH,
> Cedric

This is more complicated than you'd think. Addresses 00000-9FFFF are
standard. A0000-BFFFF as local memory cycles are used as SMRAM in modern
systems, and can be accessed only when the CPU is in SMM (ordinarily).
Otherwise, addresses in the range A0000-BFFFF depend on the system
architecture. These addresses while NOT in SMM are forwarded to the PCI/ISA
bus unless the system uses Unified Memory Architecture (UMA), whereby the
video controller uses system RAM rather than its own RAM (to reduce board
cost of extra video RAM, and eliminate the need for the entire video
adapter, which resides in the chipset itself).
  The chipset in UMA systems allocates some (usually setup-selectable, not
always) amount of system RAM as video RAM, taken from the top (high
addresses) of the installed RAM. In these systems, accesses to A0000-BFFFF
are aliased via the video controller to these high addresses. Accesses to
the address space allocated to video RAM in UMA systems (at the top of
installed RAM) are treated by the memory controller as non-local cycles,
and forwarded to the bus.
  Moving right along, some chipsets allow the creation of memory 'holes',
intended to allow devices with non-moveable memory-mapped IO. The displaced
memory from the hole is moved to the top of system RAM address space. Some
chipsets allow shadow space (C0000-FFFFF) to be mapped as a hole. Shadow
RAM attributes are usually set in 16K blocks of address space, and can be
set to Read/Write, Read Only, and disabled (forwarded to the bus).
Typically, these 16K blocks can also be designated as cacheable or
non-cacheable regions.
  Some chipsets allow for more than 128K of SMRAM (A0000-BFFFF), and map
the (additional or substitute) SMRAM above 1M. Accesses to such 'high'
SMRAM addresses are forwarded to the bus when not in SMM.
  The original IBM memory size, stored in CMOS, could describe a maximum of
64M (at that time, 256K was considered a lot of system RAM, so the 64M
limit was considered unreachable within the lifetime of the architecture).
Most BIOSs support at least one of three possible calls to get the actual
installed RAM size (not including memory allocated to UMA). These are
interrupt 15h calls 88h, E801h, and E820h. Many utilities try all 3, but
there are some BIOSs that don't support any of them.
Quote:
> --
> ***************************************************************

> * Antenna engineer - Alcatel Espace - Toulouse - France       *
> ***************************************************************



Wed, 06 Sep 2000 03:00:00 GMT  
 Video ram size and system ram size

Hi.

Quote:
> This is more complicated than you'd think. Addresses 00000-9FFFF are
> standard. A0000-BFFFF as local memory cycles are used as SMRAM in modern
> systems, and can be accessed only when the CPU is in SMM (ordinarily).
> Otherwise, addresses in the range A0000-BFFFF depend on the system
> architecture. These addresses while NOT in SMM are forwarded to the PCI/ISA
> bus unless the system uses Unified Memory Architecture (UMA), whereby the
> video controller uses system RAM rather than its own RAM (to reduce board
> cost of extra video RAM, and eliminate the need for the entire video
> adapter, which resides in the chipset itself).
>   The chipset in UMA systems allocates some (usually setup-selectable, not
> always) amount of system RAM as video RAM, taken from the top (high
> addresses) of the installed RAM. In these systems, accesses to A0000-BFFFF
> are aliased via the video controller to these high addresses. Accesses to
> the address space allocated to video RAM in UMA systems (at the top of
> installed RAM) are treated by the memory controller as non-local cycles,
> and forwarded to the bus.
>   Moving right along, some chipsets allow the creation of memory 'holes',
> intended to allow devices with non-moveable memory-mapped IO. The displaced
> memory from the hole is moved to the top of system RAM address space. Some
> chipsets allow shadow space (C0000-FFFFF) to be mapped as a hole. Shadow
> RAM attributes are usually set in 16K blocks of address space, and can be
> set to Read/Write, Read Only, and disabled (forwarded to the bus).
> Typically, these 16K blocks can also be designated as cacheable or
> non-cacheable regions.
>   Some chipsets allow for more than 128K of SMRAM (A0000-BFFFF), and map
> the (additional or substitute) SMRAM above 1M. Accesses to such 'high'
> SMRAM addresses are forwarded to the bus when not in SMM.
>   The original IBM memory size, stored in CMOS, could describe a maximum of
> 64M (at that time, 256K was considered a lot of system RAM, so the 64M
> limit was considered unreachable within the lifetime of the architecture).
> Most BIOSs support at least one of three possible calls to get the actual
> installed RAM size (not including memory allocated to UMA). These are
> interrupt 15h calls 88h, E801h, and E820h. Many utilities try all 3, but
> there are some BIOSs that don't support any of them.

This sounds _really_ complicated... does this mean that the only reliable
way of getting the total amount of RAM is to repeat the memory test that's
done during bootup?

--
 ___________________________________________________________________________
|                                                                           |

| http://wwp.mirabilis.com/8123598              http://teekiah.home.ml.org/ |
| pgp -kvc: 1024/89d8686d  0f f4 b4 d9 2e 12 c7 b2  1a 85 bc 12 8f 54 77 f1 |
|___________________________________________________________________________|



Thu, 07 Sep 2000 03:00:00 GMT  
 Video ram size and system ram size

Quote:
>>   The original IBM memory size, stored in CMOS, could describe a
maximum of
>> 64M (at that time, 256K was considered a lot of system RAM, so the 64M
>> limit was considered unreachable within the lifetime of the
architecture).
>> Most BIOSs support at least one of three possible calls to get the
actual
>> installed RAM size (not including memory allocated to UMA). These are
>> interrupt 15h calls 88h, E801h, and E820h. Many utilities try all 3,
but
>> there are some BIOSs that don't support any of them.

That may explain why my laptop, delivered with 72MB of RAM, gets a lot of
"You only have x MB of memory", where X is a low number.    This usually
happens when installing some older piece of software.  The program
usually runs, it just has a funny idea how much memory is around.

Quote:

>This sounds _really_ complicated... does this mean that the only
reliable
>way of getting the total amount of RAM is to repeat the memory test
that's
>done during bootup?

>--

_________________________________________________________________________
__
Quote:
>|
|
>| Chia Tee-Kiah                              <


Quote:
>| http://wwp.mirabilis.com/8123598

http://teekiah.home.ml.org/ |
Quote:
>| pgp -kvc: 1024/89d8686d  0f f4 b4 d9 2e 12 c7 b2  1a 85 bc 12 8f 54 77
f1 |
>|_______________________________________________________________________
____|



Fri, 08 Sep 2000 03:00:00 GMT  
 Video ram size and system ram size

Quote:

> This sounds _really_ complicated... does this mean that the only reliable
> way of getting the total amount of RAM is to repeat the memory test that's
> done during bootup?

Certainly. This is what my programs do, and is not _that_ complicated:
'just'
switch to pmode, try write/read/write_back at some positions of the
memory,
for example every 4k, and count the number of hits; add the 640k to
finish
if you started at 1Mb.

And be aware that some BIOS allow to make a memory 'hole' of 1Mb at
position
+15Mb to +16Mb, while other memory is still available above; so a more
sophisticated program would check 256Mb of RAM to build a complete but
precise RAM map.

Cedric.
--
***************************************************************

* Antenna engineer - Alcatel Espace - Toulouse - France       *
***************************************************************



Sun, 10 Sep 2000 03:00:00 GMT  
 Video ram size and system ram size

Quote:


>> For the system RAM you could use the XMS size and add 1 MB.
>Yes and no; the value will be wrong if the system has more than
>64 Mb; the best is to program a small tool in pmode that will check
>the effective available ram;

Why, XMS can use more than 64 MB.

Quote:
>I also saw on some systems that the RAM that is at A000-FFFF is
>sometimes 'moved' to the end of the physical memory, which was not
>detected by XMS, but by my program; so sometimes more memory than
>the one given by XMS is available (and usable of course !).
>HTH,
>Cedric
>--
>***************************************************************

>* Antenna engineer - Alcatel Espace - Toulouse - France       *
>***************************************************************




Wed, 13 Sep 2000 03:00:00 GMT  
 
 [ 8 post ] 

 Relevant Pages 

1. How to get VIDEO ram size

2. size of RAM

3. ram size

4. Help about detecte RAM size

5. RAM size

6. Conversion of Altera Block RAM to Xilinx Block RAM

7. Read latency of block ram disappears when ram is clocked from bufgce

8. RAM and RAM model

9. Video Ram

10. Accelerator [was Video Ram]

11. EGA/VGA Direct Write to Video Ram Routines

12. EGA/VGA Direct Write to Video Ram Routines

 

 
Powered by phpBB® Forum Software