My test was with Tiny Core 5.2 which was installed on an 8GB pen drive - and I've since used v7.2.
As you would expect with HP thin clients with a PC compatible architecture and standard BIOS there should be no problem running various flavours of Linux on the t5740. (NB See below re PAE kernels).
This was borne out by an email I received from Shantonu in July 2017. He'd tried out the i386 versions of:
He did note that, except for centOS, the display resolution selected automatically was not the best one for his monitor so "...might need to edit /etc/default/grub config to specify the display resolution."
The Atom N280 is a 32-bit processor and so can only directly address 4GB of RAM. However it does support Physical Address Extension (PAE) and so, with a suitable OS, should be able to use any additional memory installed. With the t5740 the maximum amount of RAM that can be installed is 8GB.
Most distributions offer a build with a PAE enabled kernel.
In September 2017 I tried out Puppy Linux (tahr-6.0.5_PAE.iso) and Linux Mint (linuxmint-18.2-xfce-32bit.iso). Both of these ran, but despite my t5740 being fitted with 6GB of RAM they only saw the ~3GB of RAM of a standard 32-bit operating system. As a check I booted the same USB pen drives on a 10ZiG 58xxq that was fitted with 4GB of RAM but used a Celeron CPU. In this case they reported and used the full 4GB of RAM.
I have various reports from others of their inability to use any installed RAM above the 32-bit 4GB limit. However there are two exceptions - see below.
All I can suggest is that the Intel Atom N280/GL40 combination has some quirk that defeats the standard PAE code and you are stuck with the 4GB limit irrespective of what the BIOS tells you. On this basis there would appear to be no benefit in installing more than 3GB/4GB RAM in a t5740 unless you're planning to run a compatible version of Windows Server. (See below)
At least two people have successfully used Windows Server to fully utilise fitted RAM in excess of 4GB. However I also note that Windows Server 2008 was the last 32-bit version released by Microsoft. From Windows Server 2008 R2 only 64-bit versions have been shipped.
In September 2018 I received the following email from Jordan in Indiana, USA:
I installed 32 bit Windows Server 2003 on an HP t5740 thin client and it detected 6 GB RAM (all I had installed). I was unable to get ANY other PAE-capable OS to detect the extra RAM.
In July 2019 I heard from Victor in Miami:
I have a handful of HP t5740 and t5740e thin clients and I was frustrated when I saw that the BIOS would see all of the installed RAM but no matter what OS I tried, the OS would not detect the full amount and only stick to the usual 32-bit RAM limit. I tried many configurations and made sure to confirm I was using PAE enabled Kernels on Linux and yet they still would not allow full use of all the RAM.
It was while trying to get the 32 bit, PAE enabled version of Linux Mint to work (and failing) that I came across your site and the mention of Windows Server 2003 being able to use all the RAM. That switched my attention to Windows Server, but in my quest to find an ISO I could use I was only able to find Windows Server 2003 Standard. While I did get it installed it would not use the full amount of RAM as that particular variant does not support PAE. Frustrated I put the project on the back burner for a few months.
When I picked it up again I did some research that made me realize that I could probably use Windows Server 2008 Enterprise or Datacenter Edition as these have PAE enabled. I was lucky enough to find a site with the Windows Server 2008 install ISOs available for download.
Finally I tested it and confirmed that it worked just as I wanted. Now I have my HP t5740 running Windows Server 2008 SP2 Datacenter Edition with 6GB (1 x 2GB and 1 x 4GB SODIMMs) of RAM and the OS detects and uses the full 6GB. I am planning on installing the full 8GB to check if that would work. I know this information is coming really late specially since Microsoft will stop supporting WS 2008 next year. (January 2020).
BTW I also installed a Broadcom BCM970015 CrystalHD Video Decoder which works flawlessly to play back high def videos streaming without maxing out the CPU and without stuttering.
Victor also supplied some links:
Note: These days many Microsoft ISOs are available via their Download Center. These usually offer an evaluation period where you can try them out after which you'll need a valid product key should you wish to continue using them. For example, today (July 2019) a search for Windows 2008 Server Datacenter throws up a 2.9GB download along with the following comment:
This software is for evaluation and testing purposes. The evaluation is available in ISO format. Web, Standard, Enterprise and Datacenter editions are available via the same download. You will be prompted for edition installation at setup. Evaluating any version of Windows Server 2008 R2 software does not require entering a product key, however will require activation within 10 days. Failing to activate the evaluation will cause the licensing service to shut the machine down every hour (The 10 day activation period can be reset five (5) times by using the rearm command. See below for further information on activation rearm). After this time, you will need to uninstall the evaluation software and reinstall a fully-licensed version of Windows Server 2008 R2.
I note that the Wikipedia PAE article does include the comment:
...even if no more than 4 GB of RAM is available and accessible, a PAE-capable CPU may be run in PAE mode, for example to allow use of the No execute feature.
FYI: The 4GB limit refers to total addressable memory space. This memory space, as well as being used by the system RAM, is also used by graphics RAM, PCI memory range, ACPI and a few other bits and pieces. On a system fitted with 4GB of RAM and a modest graphics card with 512MB of on-board memory the end user normally ends up seeing about 3GB of installed system RAM. So what this means is that the realistic upper RAM limit for a 32-bit OS is more like 3GB than 4GB.
Any comments? email me. Added February 2015 Last update July 2019