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Old August 17th 17, 07:50 PM posted to alt.comp.periphs.videocards.nvidia
Paul[_28_]
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Default How come RAM is taken away for video cards? Because of my videocard's VRAM?

Ant wrote:
On 1/18/2016 9:10 PM, Ant wrote:
Le Forgeron wrote:
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Le 17/01/2016 10:31, Ant a écrit :
Like I have 3 GB of RAM, but Windows show 2.5 GB. I was told
because it is a shared memory?

Thank you in advance.


Are you sure it's not 4 GB of RAM, but Windows showing only 3.5 GB ?
On a 32 bits system, some of the addressing space must be mapped to IO
board... historically, the IO were mapped at the top of the 4GB
address space (of the 32 bits), alas with 4GB memory being now
available, that trick does not work... or rather still work too well,
and then some memory cannot be used as such.


Please describe your motherboard & CPU (name them at least), and your
version of windows.


And how you get the measurement.


Sorry. I meant to say 6 GB of RAM and only 2.5 show in 32-bit WinXP Pro SP3


Details: Intel i7 950 CPU (quad-core)

(3) Kingston HyperX T1 DDR3-2000 (PC3 16000) (6 GB total; 2.5 GB shown)

EVGA X58 SLI (132-BL-E758;
BIOS date 5/11/2010; v6.00 PG; release number IX58SZ64) motherboard

MSI R4870-T2D512 OC Radeon HD 4870 512 MB (using driver v9.4)

two onboard RealTek Gigabit Ethernets (only use one)

onboard RealTek HD Audio

Hauppauge WinTV-HVR-2250 PCIe (dual tuners)

a Broadband Technologies Air2PC-ATSC-PCI HDTV tuner cards (DVB; revision 2)


Still no answers?


This diagram shows how it works. What it doesn't describe
in detail, is how the 750MB address area is used.

https://blog.codinghorror.com/conten...980970c-pi.png

So first of all, that machine would report "3.2GB free" on
an x86 install. The 750MB or so, is used for bus addresses.

Bus allocations traditionally, were done in 256MB chunks. I
think on the Mac it might have been that way too, but I've forgotten
the nomenclature.

The question them becomes:

1) How many bus segments do you have ?
Is one of the cards bridged, with a hidden PCI bus inside ?

2) Your video card uses 512MB. If you had *two* of those
video cards, then that would account more or less exactly,
for your reported 2.75GB free.

3) The Air2PC-ATSC-PCI is weird, in that it has an ASIC on board
that makes the card look like a network device. Does that
result in a unique allocation ?

https://www.linuxtv.org/wiki/index.p...ir2PC-ATSC-PCI

"As the FlexCop PCI interface chipset completely lacks
any analog input functionality, this explains why these
cards are barren of analog inputs, and also why they
appear in dmesg or lspci output only as a "network controller".
"

So if you don't have two 4870 video cards, maybe that tuner has
something to do with it.

You can use Lavalys Everest V2.20.405 to get a nice table, to start your
research with. The output looks like this, nice hex addresses. Note
that this isn't really "perfect for the purpose", but you have
to start somewhere. And other utilities aren't even getting
close to this much info. I can't see a pattern here, to
demonstrate 256MB for PCI, 256MB for PCI Express and so on.
It's possible for bus segments needing just one byte of
address space, to cause the BIOS to allocate another 256MB.

https://s11.postimg.org/wjxsssdxv/lavalys_everest.gif

Memory 00100000-BFFFFFFF Exclusive System board

Doing the hex math on calculator, conv to dec, gives 3,220,176,895 bytes

From Task Manager "Physical Memory (K)"
3144748 * 1024 = 3,220,221,952

No idea why there is a discrepancy...

Purely a guess,
Paul