As with the previous processors, the documents from HP provide some assistance.
The original service and maintenance manual for both models can also be found here:
https://www.levnapc.cz/ProductsFiles/hp-elitebook-8540p-8540w-manual-en.pdf (archive.org)
On page 60, there is an overview of the memory modules that are supported:
It’s a bit strange that the smaller modules are listed as 1600 MHz, which, to my knowledge, is not supported by any of the processors that run on the motherboard/chipset. It doesn’t make any difference; faster RAM is simply throttled down. I suspect that this made it easier for HP in terms of hardware inventory management. 1600 MHz was standard for DDR3 in many devices at that time and especially in the years that followed.
The maximum RAM for the models would be as follows:
| EliteBook 8540p | EliteBook 8540w | |
|---|---|---|
| Maximum total capacity | 16 GB | 32 GB |
| Maximum number of SO-DIMM modules | 2 x DDR3 | 4 x DDR3 |
| CPU memory channels used (internal allocation) | 2 / 2 (__ A2 + __ B2) | 2 / 2 (A1 A2 + B1 B2) |
| Position of the modules | One module under the keyboard and one under the RAM cover on the bottom | Two modules under the keyboard and two under the RAM cover on the underside |
| Maximum achievable clock | 1066 MHz with a Dual-Core CPU 1333 MHz with a Quad-Core CPU | 1066 MHz with a Dual-Core CPU 1333 MHz with a Quad-Core CPU |
Digression: RAM designs
To briefly explain, as there is often little differentiation between them, there are generally three types of DDR RAM designs, which apply to DDR, DDR2, DDR3, DDR4, and DDR5. This will likely also apply to their successors.
| Design | Description | Application | Modular / interchangeable? | Types |
|---|---|---|---|---|
DIMM | Dual Inline Memory Module | Desktop, Server | Yes | UDIMM, RDIMM, NV-DIMM, etc. |
SO-DIMM | Small Outline – Dual Inline Memory Module | Mobile | Yes | UDIMM, RDIMM |
LP | Low Power | Ultra-Mobile, Smartphones, Tablets, etc. | No | unbuffered or registered possible |
More detailed information here: DIMM
Provided that the RAM has not been soldered (which is unfortunately increasingly the case with modern devices), ONLY SO-DIMM modules fit into a notebook; in the case of the 8540p, this is the DDR3 variant.
If the notebook is to be used exclusively for Windows XP, a total of 4 GB RAM is optimal, preferably in the form of two modules with a capacity of 2 GB each (dual channel operation). As a 32-bit operating system, XP cannot address more than 4 GiB, regardless of how much memory is installed.
In our case, I am utilizing the maximum amount of RAM that fits into an 8540p motherboard, namely two DDR3L SO-DIMM modules, each with 8 GB, 1600 MHz* from the manufacturer SK Hynix, which adds up to a total of 16 GB.
After all, I’m planning a multi-boot setup, more on that later.
By choosing an i7-840QM as my CPU, I can achieve clock speeds of up to 1333 MHz – so my memory modules are throttled, but fortunately in exchange for slightly better latencies:
It is important to note that DDR SDRAM (DDR stands for Double Data Rate) specifies twice the clock rate, as data is transferred on both the rising and falling edges of each clock cycle.
However, the screenshot above shows the “real” clock rates – 666.7 is actually 666.6667 period and corresponds to 1333.3334 period MHz clock. This therefore matches the maximum capacity of the CPU (“1333 MHz”). I’m glad that these memory modules seem to have these latencies etc. stored in the SPD chip ex works and that the appropriate values for the clock are applied automatically (probably by the BIOS). Lucky me.
There are no settings for this in the BIOS of the 8540p, so it’s all the better that everything is detected and set fully automatically. Cheap no-name modules will probably not have these functionalities, or at least not completely, so be careful!
In my case, I had another, slightly newer notebook that was irreparably defective (I destroyed it myself…PROCHOT Override, burned out – another story), from which four of these bars were “left over”—ideal, two for each of the two 8540ps. I had previously purchased eight of these bars at auction for a good price (at the time) – according to the description at the time, they had been removed from Apple Mac Minis.
SK Hynix, Samsung, Micron (Crucial), and Kingston are all reputable brands; I usually tend to go with Samsung.
There are many model names, but not many memory manufacturers, so it’s best to do your research carefully.
Digression: Types of DDR3 SO-DIMMs
It is important to mention that there are two widely used versions of DDR3 as SO-DIMM in the mobile sector and one less common version:
| DDR3 | DDR3L | DDR3U | |
|---|---|---|---|
| Type | “Normal” | “Low Voltage” | “Ultra Low Voltage” |
| Voltage | 1.50V | 1.35V | 1.25V |
| Usual clocks | DDR3‐800 (PC3-6400) DDR3‐1066 (PC3-8500) DDR3‐1333 (PC3-10600) DDR3‐1600 (PC3-12800) DDR3‐1866 (PC3-14900) DDR3‐2133 (PC3-17000) | DDR3L‐800 (PC3L-6400) DDR3L‐1066 (PC3L-8500) DDR3L‐1333 (PC3L-10600) DDR3L‐1600 (PC3L-12800) | DDR3U‐800 (PC3U-6400) DDR3U‐1066 (PC3U-8500) DDR3U‐1333 (PC3U-10600) DDR3U‐1600 (PC3U-12800) |
I have never seen the “U” variant in the wild, but DDR3L is very common in devices that came onto the market later in the DDR3 life cycle. It is also backward compatible with “normal” DDR3 and can therefore be used as a direct replacement for DDR3 in most cases (as is the case with the 8540p).
But be careful:
The early CPUs of the first generation Core i, and especially those before that, i.e. Core 2 and earlier, are in exceptional cases very sensitive to RAM, which, like the processors themselves, is known to consist of silicon dies manufactured using different lithography processes.
Old processors can sometimes only handle the “older,” “coarser” RAM modules. This problem was particularly pronounced in the Core 2 Duo/Core 2 Quad era, when the basic structure of a motherboard/chipset was still somewhat different.
This also has something to do with the fact that these older processors usually had to cope with two generations of RAM (e.g., DDR2 or DDR3) and therefore simply seem to be more sensitive.
Finally, on the subject of RAM, it should be noted that there are general differences in the configuration of the individual modules, but these are not relevant in this upgrade project, as the memory controller is located in the CPU and, except for overclockable Intel processors, determines the maximum clock speed (1333 MHz for the i7-840QM, which is fixed).
For example, there are SS and DS modules, i.e., single-sided and double-sided. There are also ranks that do not necessarily follow the configuration: single rank, dual rank, and quad rank.
The whole thing is definitely a science in itself, just as RAM overclocking is a complex topic.
We continue with the most important of all upgrades, provided that a hard disk drive (HDD) was still installed.