GX280, reserving too much memory

It's true XP is the last officially supported OS for this model. But I dare Dell to show me a GX280 with XP that supports 4 GiB RAM, even if you run 64-bit XP. It's a hardware/BIOS issue, not an OS issue.

As for service and support - it's true that this model is old and discontinued but for many years it wasn't. Why didn't Dell fix the problem then?

If Dell is committed to the quality of their products, their customers and the environment they would have fixed and should fix this. The gx280 has a couple of years left in it, properly cared for. I'm using mine as a secondary machine for web browsing: it can do Facebook plus a handful of tabs no problem (Linux Mint XFCE), and adding an SSD would make it even faster.

All I'm asking is that Dell makes the machine work like it's supposed to or a otherwise confess the gx280 has a design flaw that limits RAM usage to 3 gigabytes.

Keep in mind Dell, or any PC company, is in the business of selling new PC's.  When an item is discontinued and  past its life cycle they are over and done with it.  Only in extremely rare cases will anything be revisited and your system is not the "rare case".

This has nothing to do with Dell or bios.  Its a limitation of how INTEL the Bios and PCI slots, Integrated INTEL GRAPHICS and I/0 are mapped. This is the same for  OptiPlex GX620, GX520, GX280, SX280, GX270, SX270, 210L and 170L and other models with this chipset.  You do not get the Shared Ram Back EVEN WHEN YOU ADD A VIDEO CARD.

https://www.dell.com/downloads/global/products/optix/en/spec_optix_gx280_en.pdf

XPS 400 and Precision 380 allow 8 gigs of ram. This is because their chipset does not have onboard INTEL GMA.  The GX280 and GX620 regardless of EMT64 and 64 bit os are limited to 3.2 to 3.5 gigs of ram period end.

When you have integrated video Intel® 915GV Express Chipset for older systems 4 gigs was maximum ram.  The bios and video etc are mapped to 32 bit address space. There was no 64 bit os at the time of release back in 2003. Showing ram is not the same as being able to use it. You do not get integrated ram back when you add a video card. The GX620 which is the transition from GX280 also has this limitation. In your case windows would show 4 gigs total ram and 2.99 to 3.25 usable. This us DDR 400 where 4 gigs is max total ram. There are no 2 gig DDR400 dimms. You are demanding a feature that was never available and will never be.  Chipset Limitation nothing whatsoever to do with Dell or Bios. Many of the CPU's at the time were also 32 bit only.

https://ark.intel.com/products/27469/

EM64T, NX, Hyper-Threading etc were added later by Intel.

Dell never bothered to make a 64 bit bios let alone a 64 bit memory map when 2 GIG DDR 400 dimms were never available in un registered un buffered non ecc.

 Thats also why its pointless to add a 64 bit os to these older systems.

GX620 is the best update for using all the old parts from your GX280.

https://www.walmart.com/ip/REFURBISHED-Optiplex-GX620-Tower-400GB-HDD-4GB-Ram-DVD-Rom-Windows-7-Professional/699129865

It may well be true on your GX620 which has the 945G chipset. I can see that 3,5GiB is available to your OS and with that slightly newer hardware it stands to reason that the system steals half a gigabyte for the GPU.

But in my machine it´s not 3,5GiB but closer to 3 left. And it has the 915G chipset. Can you prove that it is an issue of shared GPU memory? In the GX280 BIOS settings you can choose to preallocate 1 or 8 MEGAbytes of memory. Booting straight to Memtest, still only 3 gigabytes of memory seems to be available for testing. Booting the OS I can see in the log that about 200 megabytes of shared memory is available for drm (graphics). So even if you subtract 208 megabytes of shared memory - where is the rest? Still about 700-800 megabytes missing.

That is with Server platforms with different memory map. Your original post complains about something that is by design.  Its not a problem that will ever be fixed because its not even possible to get more than 4 1 gig dimms working on the original DDR 400 GX280.

Where do you propose to get 2 GIG  DDR 333 DDR 400 Dimms for the GX280 when max ram is 4 gigs total with 4 slots.  

https://www.datamemorysystems.com/dms-memory/dell/optiplex-gx280-smt.htm

There are Mr Smith GX280's which are essentially GX620 towers that have a GX280 badge on them and support DDR2.   The older GX280's in the Skydive Mini Tower Case are the DDR400 models. Again you are demanding something that was never made.

Even the Later GMA 945 in the GX620 while it recognizes 2 gig DDR2 dimms in bios no os can use more than 3.50 gigs total ram due to INTEL CHIPSET limitations with GMA.

When you take the same Ram and CPU and move to a Precision 380 or XPS 400 you get the full 8 gigs because those systems DO NOT HAVE INTEGRATED MEMORY STEALING Graphics or 4 gig chipset memory map limitation.  The Mid Tower became GX620 and the Small Mid Tower is the OLD GX280 with DDR400 max.  There are only 4 ram slots and DDR 333/400 is 1 gig per Dimm Max.  8 gigs is NEVER an option.

 GX280 Versions

The GX280 that I have is running with 4x1GiB DDR2 533MHz DIMMs. I think the 915G chipset should be able to handle up to 8 GiB DDR2 memory:

https://ark.intel.com/products/27733/Intel-915G-Graphics-and-Memory-Controller

I can also mention that I have a P4 640 64-bit processor, allowing me to run a 64-bit OS.

Well, my problem was not installing 8 GiB of RAM if this computer. And again, I have DDR2 memory so I don't see why you keep writing about DDR 400. My problem is not being able to use more than 3 GiB of RAM when 4 GiB is installed. You refer to this being because of the IGP stealing memory, which I belive I have proved not to be the explanation. You also point to the old chipset using 32-bit adressing, but 32-bit addressing should be able to adress the full four Gigabytes.

The only thing of which we both seem to be able to agree, is that only 3 Gigabyte of memory is available to my OS although 4 is installed.