The HP t5135 I have was manufactured in February 2007. As far as the hardware is concerned the t5135 appears identical to the t5530 in every way except for the CPU that is fitted to the circuit board.
64Mb (? max)
1600 x 1200 32-bit colour
8 x USB2.0
KYBD & Mouse
12V 3.33A (from label)
Dimensions W x H x D 53mm x 185mmm x 185mm Security Kensington Lock Slot
The embedded operating system is HP ThinConnect.
For those to whom it matters here is some detail from Linux's /proc/cpuinfo
vendor_id : CentaurHauls cpu family : 6 model : 10 model name : Via Esther processor 400MHz stepping : 9
The unit requires a 12V supply with a 5.5mm/2.1mm coax plug. If yours came without one a unit can be easily sourced on ebay. In the past I've bought a 12V 3.3A unit on ebay that was advertised as being a replacement one for an LCD display.
RAM: The RAM is soldered to the board and so fixed at 128MB.
Flash: The Flash memory is a DOM (Disk On Module) fitted to a standard 44-pin IDE connector. This can be removed and Compact Flash cards or laptop hard drives can be connected in its place. My only observation here is that, using a conventional IDE plug, there is zero clearance between the plug and the internal metal case of the t5135. If you're not careful you may end up fitting the plug shifted over by one set of pins - as I did the first time!
usb: As well as 6 external sockets there are two USB ports located under the top cover. An ideal location for adding something like a USB wireless device.
Click on the photo for a larger version.
From an HP briefing document:
"Going forward, new t51xx and t55xx thin clients will not have configurable RAM. For manufacturing economies of scale, RAM will be installed "down." The t51xx and t55xx units will not include a SODIMM slot."
Any comments? email me. Added April 2012