RAM 'Hardware reserved'

[RVB]

My computer had 4x 2GB (8GB) RAM and always used to show 164MB RAM as hardware reserved, 7.8GB usable.

If I upgrade to 2x 2GB + 2x 4GB (12GB) RAM it also shows 164MB RAM as hardware reserved, 11.8GB usable.

But if I fit 4x 4GB (16GB) RAM my computer says 1GB hardware reserved, 15GB usable.

Why does it 'reserve' so much more if 16GB is fitted compared to 12GB or 8GB?

All the RAM modules are the same manufacturer, similar manufacture date (year 2012), same timings etc; the only difference being 2GB single-rank modules or 4GB dual-rank modules. Computer is Dell Optiplex 780, Core2 Quad Q9400, Crucial 1TB SSD, Windows 11.

[21TonyK]

My god, who remembers "reserved ram" above 512K.

Sorry for the diversion op!

[Harpoon]

Does the PC have integrated graphics? Might be worth a look in the BIOS but 16Gb RAM might see it allocate additional RAM for graphics.

21TonyK said:

My god, who remembers "reserved ram" above 512K.

Sorry for the diversion op!

Remember to load himem.sys & emm386.exe with the right parameters...

[RVB]

Harpoon said:

Does the PC have integrated graphics? Might be worth a look in the BIOS but 16Gb RAM might see it allocate additional RAM for graphics.

Yes, integrated graphics.

I wondered if that might be the reason but surely ~12yr old integrated graphics can't make use of the 1GB RAM that's being reserved?

[Mr E]

21TonyK said:

My god, who remembers "reserved ram" above 512K.

Sorry for the diversion op!

Amiga. Chip ram and fast ram.

[essayer]

2010s graphic cards regularly came with 1GB/2GB for textures etc, quite possible for that to be used on games of that era

[RVB]

essayer said:

2010s graphic cards regularly came with 1GB/2GB for textures etc, quite possible for that to be used on games of that era

Interesting, thanks.

Why is it reserving such a chunk of RAM? I thought the integrated GPU just borrowed whatever RAM it needed at the time.

When playing old games, would there be any noticeable difference between 16GB (1GB reserved) vs 12GB (164MB reserved)?

[CorradoTDI]

I've come across this before and I think it's to do with the way the RAM is channelled when it's matched... not sure you can do anything about it tbh so I'd just forget about it but If you search the registry for this key it might show it - DedicatedSegmentSize

[Jinx]

Harpoon said:

Does the PC have integrated graphics? Might be worth a look in the BIOS but 16Gb RAM might see it allocate additional RAM for graphics.

21TonyK said:

My god, who remembers "reserved ram" above 512K.

Sorry for the diversion op!

Remember to load himem.sys & emm386.exe with the right parameters...

DOS = High

(shove it into the area between 640KB and 1MB)

[CobolMan]

Takes me right back to the good old days of every game having it's own entry in config.sys and autoexec.bat. Anyone else remember himem.sys?
My apprentices can't believe what we used to do to get games running nor that 1 Meg of RAM would cost £25.