A fanless industrial PC can carry two temperature ratings, not one. On Seatronx’s MP-3700 page the top of the range is 70°C with the 35W CPU and 60°C with the 65W CPU. That top number is the ceiling: the highest temperature the page states for working. So the CPU option sets the ceiling, and you choose against the hottest temperature the computer will work in.
If the hottest temperature stays at or under 60°C, both options sit inside the page’s stated ceilings, and the choice can follow the processing the work needs. If it can pass 60°C but stay under 70°C, only the 35W option’s stated ceiling covers it. Above 70°C, neither stated ceiling does.
A computer put in a space hotter than the ceiling its page states can run outside its stated range in the hottest hours. Swapping the CPU option then means a second order. This is general planning guidance and not engineering advice, so the project’s engineers and the supplier confirm what applies.
Why the CPU Option Moves the Rating on a Fanless Industrial PC
Fanless means there’s no fan in the computer. Nothing blows air across the processor, so the housing has to hand the heat to the air around it. As a general rule, a processor that gives off more heat leaves less room before the housing is too hot for the space. That’s one way a higher CPU power can go with a lower stated ceiling on a fanless industrial PC.
The wattage in a line like “(65W/35W TDP)” is a power and heat figure. TDP is thermal design power, the power number a processor’s maker gives for choosing cooling. Intel’s support article on Thermal Design Power says it “stands for Thermal Design Power, in watts, and refers to the power consumption under the maximum theoretical load.” The point of the figure, the article says, is to give system designers and integrators a power target for picking a thermal solution. Under lower loads, the article says power consumption is less than TDP.
That’s a target for the people designing the system. The article says nothing about an enclosure, a fan or the air in a compartment. The link between watts and a stated ceiling is the product pages’ own pattern, and the MP-3700 page is the plain case: the lower ceiling sits with the 65W CPU.
The chassis side of a fanless computer is its own subject. Seatronx’s article on why marine computers outlast office PCs on the bridge covers that.
What the MP-3700 Page States for Each CPU Option
Seatronx’s MP-3700 page lists a wide operating temperature of -25°C to 70°C for a 35W CPU and -25°C to 60°C for a 65W CPU. The full feature list is on Seatronx’s MP-3700 rugged marine computer page. That list gives the processor options as “(65W/35W TDP),” and the page calls the unit “A superior fanless system.” Two ceilings, one chassis, and the CPU option is what separates them.
The page states its range in two places, and they read differently. The opening paragraph says the series offers “high reliability even operating in extreme temperatures,” and gives the range as -25°C to 70°C with no CPU named. The feature list is where 70°C is tied to the 35W CPU and where 60°C appears for the 65W CPU. Read the opening range as the upper bound for the series. Read the feature list when you’re choosing between the CPU options, because that’s the part that names the CPU.
So the CPU option isn’t only a processing decision on this chassis. It carries a temperature number with it, and that number is what the install has to live inside.
The Ratings Side by Side
The MP-3700 isn’t the only Seatronx computer page that puts a CPU power next to a temperature line. Seatronx’s MPC-3900 marine computer page calls it “This fanless embedded system,” lists “(65W/35W TDP)” for processor support and gives “Operating Temperature: -25°C to 70°C (varies by series).” That line covers the series rather than one CPU power, so which ceiling goes with each option is a question to put to Seatronx. The MPC-3800 and MPC-3850 pages each list “(35W TDP)” and tie -25°C to 70°C to a 35W CPU.
| Seatronx page | CPU power the page lists | Temperature the page states | What to ask |
|---|---|---|---|
| MP-3700 (the page calls it a fanless system), 35W CPU. | 35W CPU, from the page’s (65W/35W TDP) line. | -25°C to 70°C. | Is 70°C the air around the computer, or a point on the computer itself? |
| MP-3700, 65W CPU. | 65W CPU, from the same (65W/35W TDP) line. | -25°C to 60°C. | Which conditions go with the 60°C figure? |
| MPC-3900 (the page calls it a fanless embedded system). | (65W/35W TDP). | -25°C to 70°C (varies by series). | Which ceiling goes with each CPU power here? |
| MPC-3800. | (35W TDP). | -25°C to 70°C (35W CPU). | Is there a higher CPU power option for this page, and what ceiling does it carry? |
| MPC-3850. | (35W TDP). | -25°C to 70°C (35W CPU). | Does this page have a higher CPU power option, and what ceiling goes with it? |
Read each row as what that one page states, and nothing further. A figure on one page doesn’t carry across to another. The question in the last column is the one that closes the gap.
Which CPU Option Fits Which Space?
Match the option to the hottest temperature the space reaches, not the average. If the space can pass 60°C, the 35W option is the one whose stated ceiling covers it. If the space stays under 60°C, both stated ceilings cover it, so the work the computer does can decide. Measure before you choose.
Choose the 35W option if the space can pass 60°C. A closed cabinet, a compartment on the engine-room side, a console in direct sun: as a general rule a closed space can run hotter than the room around it. Of the two options the MP-3700 page lists for this fanless industrial PC, the 35W CPU is the one whose stated ceiling covers temperatures above 60°C.
The 65W option is on the table if the hottest hour stays under 60°C and the work needs more processing than a 35W part gives. Wattage alone doesn’t tell you how much more processing you get, so that’s worth asking. For reading a CPU spec, start with Seatronx’s article on how much CPU power a marine bridge computer needs.
If nobody has measured the space, measure the hottest hour before you pick. A guessed ambient makes the whole comparison a guess. Log the temperature in the spot where the computer will sit, through a hot day, with the doors and covers the way they’ll be in service.
If the space can pass 70°C, neither stated ceiling on the MP-3700 page covers it. Ask Seatronx what else fits, and give the hottest temperature you measured when you ask.
Where the Numbers Stop
The 35W option buys the higher stated ceiling and gives up the 65W option. That’s the honest trade. How much processing sits between the two is a question for Seatronx, because the pages give the options as power figures, and watts don’t describe processing.
The figures are ceilings, not promises about how the computer behaves near them. A page can state a limit without describing what happens close to it. So ask what the computer does when it reaches the ceiling, whether it slows down or shuts down. Ask how the figure was measured, too.
A listing on a product page is the supplier’s statement, and you can ask for what sits behind it: the conditions each figure was taken under, and the supporting data. With a fanless industrial PC, those conditions matter as much as the figure itself.
Frequently Asked Questions
What does TDP mean on a computer page?
TDP stands for thermal design power. The support article on Thermal Design Power describes it as the power consumption in watts under the maximum theoretical load, and says the point of defining it is to give system designers and integrators a power target for choosing a thermal solution. For newer generations, that article says the term is replaced with Processor Base Power, so a data sheet may print that name instead. A TDP figure is a power number, not a temperature rating.
Does every Seatronx computer page tie its rating to the CPU?
Not in the same way on each page, so check the page for the computer you’re ordering. The MP-3700 page states both ceilings and names the CPU power for each one. The MPC-3800 and MPC-3850 pages each tie -25°C to 70°C to a 35W CPU. The MPC-3900 page lists “(65W/35W TDP)” and says its operating temperature varies by series, so ask Seatronx which ceiling goes with which CPU power.
Can the 70°C figure apply to a 65W CPU in the MP-3700?
The MP-3700 page states -25°C to 60°C for the 65W CPU, so that’s the figure to plan against for that option. The 70°C end of the range sits with the 35W CPU on the same page. Any other pairing of a ceiling and a CPU power on that chassis is a question for Seatronx, and it’s worth getting the answer in writing before the order goes in.
Does operating temperature mean the air around the computer?
The pages say “operating temperature.” A figure like that can describe the air around the computer or a point on the computer itself, and the two aren’t the same once the box sits in a closed space. Ask Seatronx how the figure is defined and which conditions it was taken under.
What to Ask Seatronx Before You Pick a CPU Option
A few answers settle the CPU option, so put them in writing.
- Is the stated ceiling the air around the computer, or a measured point on it?
- Which conditions go with each stated ceiling: airflow, mounting, sun load, altitude?
- What does the computer do when it reaches the ceiling?
- On the MPC-3900 page, which ceiling goes with each CPU power?
- Do the MPC-3800 or MPC-3850 pages have a higher CPU power option, and what ceiling does it carry?
- Which of your pages states each of these?
With the hottest hour logged and the two options in front of you, send Seatronx the hottest ambient the computer will see and the CPU power you’re weighing.
