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Mac Plus - Extra RAM & Overheating?

dcr

Well-known member
This is something that has stuck with me for a long time. I'm guessing since sometime in the late 90s.

The claim was that having more than one MB of RAM in a Mac Plus could cause overheating issues. I don't remember if this pertained to general usage or usage in a server environment as, way back then, my FirstClass BBS initially ran on a Mac Plus. Seems to me, however, they were talking about general usage and not just when the machine was running 24/7.

At any rate, that tidbit of info has long stuck with me. I currently have two Mac Plus systems that have more than one MB of RAM. I think one has 2.5 MB and the other has 4 MB. I have a Kensington System Saver on both of them, so overheating shouldn't be a problem and neither one is running 24/7 anyway.

Bottom line is that I am curious if that is true or not because I haven't seen many people mention it as a problem.
 

Iesca

Well-known member
According to Larry Pina, the issue of overheating in the Mac Plus and earlier was often related to the climate in which the user was operating the machine. I don't recall what if anything he mentioned about extra RAM contributing to the problem. But his recommendation was to upgrade C1 on the analogue board as Apple had originally used too low a Voltage for that (non-polar) capacitor, and it often wasn't able to withstand the heat.
 

Iesca

Well-known member
If you have a System Saver installed on them, they should be good I would think.
 

cheesestraws

Well-known member
The claim was that having more than one MB of RAM in a Mac Plus could cause overheating issues

I mean, perhaps, but everything else also makes a Plus overheat. They just ... run far hotter than they should, in general. That's one of the major reasons why the solder joints on the AB crack, because of the large swing of the heat/cool cycles as the machine is turned on and off. They should have had a fan. They didn't. So it goes.

That said, unless you're running it a lot - 24/7 or, worse, like a desktop you turn on every morning and turn off at night (because then you get the heat/cool cycle), it's probably not a huge worry for hobbyist type purposes.
 

dcr

Well-known member
If you have a System Saver installed on them, they should be good I would think.
That was my guess as well. Plus, I don't know that I really do anything too taxing on it. It's not like I'm using it for Photoshop.

That said, unless you're running it a lot - 24/7 or, worse, like a desktop you turn on every morning and turn off at night (because then you get the heat/cool cycle), it's probably not a huge worry for hobbyist type purposes.
Probably only running it an hour or two at a time.
 

loplop

Well-known member
I recall primary sources of info back in the day (magazines, mostly) suggested that overheating was mostly related to stuffing additional components into the Plus, such as accelerators, HD's, etc.

I don't ever recall the amount of RAM itself being an issue, and to be honest that doesn't add up--RAM itself doesn't really generate a lot of heat, you know? Mildly warm is all I can recall.

Now if you were running software that used up all 4MB of ram, that suggests some heavy load, and maybe that would cause heat? I suspect the AB is a much larger cause of heat, though.
 
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desertrout

Well-known member
That scans. Accelerators were usually installed with fans for this reason. My accelerated Pluses run noticeably hotter than the non-accelerated ones.
 

cheesestraws

Well-known member
I was assuming that it was because adding more RAM on physically bigger SIMMs did something to the airflow—what little airflow there is in that case, anyway.

Probably only running it an hour or two at a time.

I wouldn't worry about that at all, personally. That's about how I run mine and I've not had issues.

It's probably useful here to distinguish between "chronic" overheating issues, where the machine slowly cooks itself, and acute ones where the whole thing suddenly goes into some kind of thermal meltdown. The Plus without accelerators or extra heat sources does the former, and this has a slow toll on things like liquid-filled caps and solder joints. In my experience, this more harms the reliability of the machine, rather than meaning that it will suddenly break and never work again, and the number of "mostly working except for solder joints" Pluses out there would seem to back that up a bit.

Runaway overheating is more dangerous for a machine, but I've never had a Plus do that, personally. It's just long-term thermal stress.
 

Skate323k137

Well-known member
I just upgraded my Plus from 1MB to 4MB, can't see an upgrade affecting any airflow given it was already 4x Simms anyway.

Has anyone stuck a small fan in theirs anywhere? I have some tiny 40mm noctua fans, might be able to cram one in there for longevity.
 

MOS8_030

Well-known member
Early Macs getting too hot in certain environments was they used to make things like the Kensington System Saver.
 

loplop

Well-known member
I just upgraded my Plus from 1MB to 4MB, can't see an upgrade affecting any airflow given it was already 4x Simms anyway.

Has anyone stuck a small fan in theirs anywhere? I have some tiny 40mm noctua fans, might be able to cram one in there for longevity.
Not Macintosh's, but I have retrofitted fans to various bits of ancient tube technology over the years. Effectiveness is largely dependent upon how well you can improve convective cooling. The Kensington design is likely a good one, as it encourages more convective cooling by its placement and operation.
 

joshc

Well-known member
Pluses run hot because of all the components on the analog baord which run hot, namely the flyback transformer but also transistors/mosfets. All that heat is only drawn out of the case by ordinary convection, rather than having any active cooling like a fan, which it really should have. I wouldn't worry it for 2-3 hours use at a time, though.
 

dcr

Well-known member
The other nice thing about the Kensington System Saver for the Mac Plus is that it gives you two additional outlets for external hard drives, printer, etc. Beat that, MacChimney! ;)
 
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