Upgrading another HP EliteDesk 800 G3 SFF

[NonSequitur777]

Dear Community,

One of the most versatile and most affordable Small Form Factor (SFF) computers available via eBay these days is the HP EliteDesk 800 G3 SFF. I have purchased and upgraded this particular PC before, but that was more of a proof-of-concept 'Frankensteinian' project.

This time around, the idea is to keep all computer components confined within the PC case.

Without further ado, here is what I got so far:

Bid and purchased this PC (1QT81US#ABA) for just $31 via an eBay Seller. It came with an i5-6500, one 8GB DDR4 2400 MHz UDIMM RAM stick and a 180-watt power supply.

First order of business when the unit arrived (and it came in very good condition) was to take it apart and cleaning it with 99.9% electronics grade Isopropyl alcohol. Removed the processor and upgraded it with an i7-7700K, which is the very best compatible CPU for this model. Because this 91-watt TDP processor runs hotter than the standard 65-watt TDP stock processor, I also upgraded the CPU heatsink/cooler with a certified 95-watt cooler, with p/n: L04397-001 "Heatsink Gen Intel 95W ENT18 S".  This is unfortunately an expensive heatsink, and difficult to get.

Next, I upgraded the stock 180-watt power supply with a 250-watt power supply with p/n: 901760-004, though I may use a 400- or 500-watt power supply if needed.

Added another 8GB DDR4 2400 MHz UDIMM RAM stick, though I will probably install 2x16GB RAM sticks when I get to it.

Installed a 500GB Samsung 970 EVO Plus M.2 NVMe SSD as the primary (boot) drive (added a heatsink too) and a 500GB Samsung 870 EVO SATA SSD as a secondary drive.

Installed a Nvidia Quadro P620, but I have ordered a low-profile RTX 3050, waiting to receive/install it.

Installed a low-profile TL-WDN4800 N900 Wireless Dual Band PCI Wi-Fi card.

Upgraded the PC with the most recent BIOS version (02.50) and upgraded TPM 1.2 to TPM 2.0 and optimized various Windows and System parameters.

Installed Windows 10 Pro and then Windows 11 Pro (25H2).

Userbenchmark performance link: HP EliteDesk 800 G3 SFF Performance Results - UserBenchmark.

Kind Regards,

NonSequitur777

[NonSequitur777]

Esteemed Forum,

Installed 4x16GB of Teamgroup "T-Force Vulcan Z" DDR4 PC4-28800, 3600 MHz, UDIMM RAM sticks running at 2400 MHz and in Dual Channel mode -yes, maxing out RAM for this PC. Btw, I had this 4x16GB DDR4 3600 MHz RAM kit in storage, and not only is it very difficult to find this quality RAM these days, if you do find it, it is priced obscenely high, like this purchase offer for just 2x16GB shows...

Also swapped the 250-watt power supply with a 310-watt power supply (p/n: L08262-002).

Userbenchmark link: HP EliteDesk 800 G3 SFF Performance Results - UserBenchmark.

Kind Regards,

NonSequitur777

[NonSequitur777 · Accepted solution]

Dear Community,

Update: been waiting for the RTX 3050 to arrive from Amazon since I placed the order on December 31st, and it appears it will show up today. When I get to it, will install this still reasonably priced card ($199.99) in the HP EliteDesk 800 G3 SFF.  Given the length of this card (174 mm or 6.9 inches in 'freedom' units), I will likely have to make a cut -pardon me: a mod in the case's drives bay in order to make this card fit. Will add that in this post, including a picture.

[EDIT:] Actually, in order to install the MSI GeForce RTX 3050 LP OC 6GB GDDR6, I did not have to modify (aka cut) into the drives bay after all -I only had to remove the "HP S8-908709 EliteDesk G3 800 SFF Hard Drive Mounting Rail Release Bracket" (I'm holding it in the picture), and only because it barely touched the card. It was easily removed (easily slid out), no forcing necessary and I don't need it anyway.

The Userbenchmark scores were quite good, considering what I worked with.  The graphics card can be further optimized/tweaked, using the GPU Tweak III "Ultimate GPU Tuning Tool", but will do that another time: HP EliteDesk 800 G3 SFF Performance Results - UserBenchmark.

Warm Regards,

NonSequitur777

[Luc751]

Hello there. Thank god i found you. Your work on the EliteDesk 800 G3 is impressive. I hope you can help me.

I intend to run my elitedesk 800 g3 sff as a local AI server for home use. Maybe also use it as a NAS. I had recently bought an NVIDIA  Tesla m40 12 GB and a Tesla P100  16GB last year when they were still cheap. . They are both data center gpus. I power them out of an 850 W psu separate from the SFF's psu. The problem is that when I install either or both of them, the bios complains about having "insufficient resources" to run the dedicated gpu/s and won't even post. It just loops me back to the bios setup. Did you ever encounter this problem? If so, what exactly was the solution?

Processor Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz (3.60 GHz)
Installed RAM 64.0 GB (63.4 GB usable)
System type 64-bit operating system, x64-based processor
Windows 11 Home Single Language 24H2
BIOS P01 ver 02.5

Thank you for your help.

[NonSequitur777]

@Luc751,

Welcome to our HP Community forum!

To the best of my knowledge, this is a known and repeatable platform limitation with the HP EliteDesk 800 G3 SFF, and your symptoms match it precisely.

Short answer: nothing is "wrong" with your GPUs or PSU wiring —you're running into a firmware + PCIe resource allocation ceiling of this SFF platform, made worse by datacenter GPUs.

Below is the exact breakdown and the realistic solutions.

What's actually happening

1. PCIe MMIO exhaustion (aka "Insufficient Resources"):

The 800 G3 SFF has a very constrained PCIe MMIO address space. Datacenter GPUs such as Tesla cards request far larger BAR regions than consumer GPUs.

When the BIOS tries to allocate:

• iGPU

• PCH devices

• NVMe / SATA controllers

• USB controllers

• Tesla GPU BARs

…it simply runs out of address space and drops you back into BIOS.

This is a pre-POST failure, so Windows never gets involved.

2. No "Above 4G Decoding" support (critical):

Bottomline: the G3 generation does NOT expose Above 4G Decoding / Large BAR support in firmware.

That feature is what allows:

• BAR remapping above 4 GB

• Datacenter GPUs to initialize cleanly

Without it → Tesla cards frequently fail to POST.

Later HP platforms (G4+, Z-series) added this. The G3 apparently did not.

3. Tesla-specific firmware issues (very important):

Tesla M40

• No native UEFI GOP

• Requires legacy CSM or a flashed GOP

• HP G3 firmware does not tolerate legacy VGA devices well

Result: near-guaranteed POST failure

Tesla P100

• Has UEFI GOP

• Still requests very large BAR space

• Often still fails on G3 SFF systems due to MMIO limits. 

4. BIOS version doesn't fix this:

I noticed that you’re on an older BIOS version 02.05, but even the latest G3 BIOS (02.50) does not remove this limitation. HP never back-ported large BAR support to this platform.

This is a design constraint, not a bug.

Things you can try (low success rate, but worth attempting)

If you want to experiment before abandoning the platform:

BIOS settings

1. Primary Video Adapter → Intel iGPU

2. Disable CSM / Legacy Support (pure UEFI)

3. Disable unused onboard devices:

   • Serial port

   • Parallel port

   • WLAN / BT (if present)

   • Unused SATA controllers

4. Remove all other PCIe cards

This might allow a single P100 to POST, but odds are still poor.

OS choice matters (after POST)

If it does POST:

• Linux (Proxmox / Ubuntu Server) handles Tesla cards far better than Windows

• Windows 11 adds additional ACPI + security overhead

However, Windows 11 is not your blocker here — you're failing before the OS loads.

What actually works (proven solutions).

Option 1: Use a different system (recommended):

Tesla cards are happiest in:

• HP Z440 (my favorite!) / Z640 / Z840

• Dell Precision 5810 / 7810

• Any workstation with:

  • Above 4G Decoding

  • Full x16 slot

  • Server-class BIOS

This is the correct solution for Tesla GPUs.

Option 2: Switch to a consumer Nvidia GPU:

If you insist on keeping the 800 G3 SFF:

Cards that usually work:

• GTX 1660 / 1660 Super

• RTX 2060 / 3060 (with power mods)

• T600 / T1000 (excellent for AI + NAS, low power)

They:

• Have small BARs

• Are UEFI-native

• Don't trigger MMIO exhaustion

Bottom line:

• You did nothing wrong

• The HP EliteDesk 800 G3 SFF firmware cannot reliably enumerate Tesla GPUs

• External PSU does not solve PCIe address-space limits

• This is a hard platform wall

If your goal is a home AI server + NAS, the Tesla cards are excellent —but they belong in a workstation-class chassis, not a G3 SFF.

Hope this was helpful.

Kind Regards,

NonSequitur777

[Luc751]

You reply mighty quickly. Absolutely amazing. Thank you.

Yeah I figured the mmio snag early on but was hoping some bios tweak to expose the above 4g setting can be found. It looks like Imma buy that g4 mobo on ebay after all. But i'll set this g3 aside for later attention, for when some other dude out there finds a way around the mmio issue.

By the way, as a Lenovo M910s came with the 800 g3 when I got it, I set out to play around with that one (which is exactly the same setup as the g3). It's there where i encountered the mmio snag. And when I tried the Teslas on the G3, yep, the snag's there too.

Here's a pic of the Lenovo M910s. I intend to do the same to the G3. I know there is a really awful place in hell for me for doing this. Lol.

Thanks for your reply, man. It slapped me to reality before I headed down the rabbit hole, likely, in vain.
Imma stay in this thread though. For sure.

Cheers!

 

[NonSequitur777]

@Luc751,

You are most welcome -glad I could assist!

Your picture made me smile: looks very much like my 'earlier' PC builds -lots of fun memories!

Smooth Sailing,

NonSequitur777

[DGroves]

HP systems in general have always had limited BIOS resource allocation issues due to HP only allowing a limited space for add in cards that reserve bios address space and  for some reason HP has not changed their stance on this

i ran into this when installing a Seagate "WarpDrive pci-e data center SSD in a Z820 that was configured for the HP bios defaults we had to disable one of the settings to free up bios space for the warpdrive and settled on disabling both the serial port and the network boot rom just to be sure future bios updates would not trigger a resource space message

[Luc751]

I think in the case of the ED 800 G3, this tweak won't sail. I tried physically removing stuff, in addition to those removable in BIOS (disabled), no dice.

I'm waiting for my Gigabyte GA z270 hd3 board to arrive. Maybe the CPU , ram and the Teslas would fare better on that one.

Even then, thanks. Having people responding to me while in a brain fog is always good.

Cheers, y'all!