RAM Upgrades

Hey everyone, I could really use some help here. To give you the quick rundown: I’ve got 8GB of RAM installed, and when I boot up my 64-bit macOS, it recognizes the full amount. However, even though it says 8GB is installed, it shows in parentheses that only 4GB is actually usable. I already tried swapping the sticks around and both modules are working perfectly fine. I'm running Corsair Vengeance LPX 2x4GB in two slots on an ASUS ROG Maximus motherboard. I also took a peek in the BIOS, and it’s only reporting 4GB there too. So, how come the BIOS is seeing 4GB while macOS claims 8GB is installed?🤷

Are we talking about identical modules here? Did you pick up some kind of bundle or what? It was working fine before, and now—suddenly—it’s just dead? Give me some actual details to work with. Since you're running into BIOS issues, we're looking at a failure somewhere in the chain—either the RAM itself is acting up or there's a problem with the motherboard.

Does everything run smoothly when you've only got 4 GB installed? And have you actually cycled through all four possible slot combinations yet?

The RAM modules are identical since I bought them as a set. Everything was working perfectly fine until just yesterday, but then I decided to give my PC a little cleaning. I didn't touch anything except for the internal fans, but once I powered it back up, things went sideways. Windows boots, but it’s showing 8GB total with only 4GB being usable. I tried a quick restart and checked the BIOS, and yep, it’s only detecting 4GB there too. I played around with the sticks, testing one at a time. If I put a single stick in the first slot, it recognizes it just fine. If I swap it to the second slot, it works too. But the moment I try to run them together using both slots, I get nothing but a black screen. The PC still turns on—all the fans spin up and there aren't any weird beep codes or anything like that—but it just won't post. So basically, before the cleaning, everything was solid, but now 4GB of my RAM has seemingly vanished into thin air. I already messed with MSCONFIG, but no luck. When the limit is unchecked, it says 8GB, but as soon as I hit apply and reboot, it goes right back to the same problem. I've pretty much cycled through every troubleshooting step I can think of. To sum it up: the RAM sticks work individually in either slot, but they refuse to play nice together in both slots at once. Hopefully, that makes sense. Oh, and I even tried flashing the BIOS, but that didn't help the detection issue, so I just flashed it back to the original version.

So, for some reason, the second RAM slot on this board is totally dead. I mean, it might not have anything to do with the cleaning process—could be anything—but I’m honestly worried you might have fried the whole motherboard. Did you mess around with the Northbridge at all (you know, that chip sitting under the tall blue heatsink right between the CPU socket and the PCI slot)? Also, did you end up pulling or disconnecting anything else while you were cleaning, besides just the fan?

I haven't even touched anything inside, honestly. I just grabbed some Q-tips and the vacuum and gave it a quick, gentle cleaning. But man, it’s tripping me out how Windows sees all 8GB while my BIOS acts like it isn't even there.

BIOS update? Is there actually anything newer out there than what I'm running right now?

M5A78L-M-LX-V2-ASUS-1401, mine was a 902

Hey Benjamin King2, would you mind taking a look at this? It says I'm running in single channel mode, but it's actually detecting both memory slots. Any idea how I can get it switched over to dual channel?

There’s nothing you actually need to toggle—dual channel kicks in automatically the second you snap two modules into the board. I don't know what the deal is, but it looks like one of your slots is just dead.

Alright, thanks for the help! If I can't get this thing running, I might just toss it in the trash, but let me know if there's another model you'd recommend picking up instead. Since it looks like all these components are pretty much sold out everywhere now, I'd love some advice on what to grab next.

You’ve got a similar model here: http://www.newegg.com/p/motherboard-example

Do me a favor and dig into the BIOS—check the clock speeds, the latency, and the voltage on that RAM—just to make sure everything actually matches what's printed on the module stickers.

Everything is set to automatic—it’s been that way since I first set things up, and honestly, I don't really care to mess with the deep technical side of it. The only weird thing I’ve noticed is that if I check my RAM, it shows up as 1333MHz, but then CPU-Z claims it's running at 667MHz.

It’s fine—honestly, we’re just looking at two different ways of reading the exact same set of data.

So I’ll just grab a different motherboard and call it a day. Thanks so much for the help!

I would check the CMOS battery first. It might be failing, which could be causing all these issues.
Sometimes things just glitch out and mess up the CMOS settings on their own.
That leads to the PC acting up—failing to recognize RAM properly or causing all sorts of other headaches.
If the Bateria still holds at least 3.15 Volts—ideally 3.20 Volts or higher—try resetting the BIOS and reconfiguring your settings to see if stability returns.
If the Bateria is weak, buy a new one. You'll still need to perform a reset after replacing it.

1. Go ahead and reset your BIOS back to the default settings just to see if that clears things up.
2. Pop those RAM sticks out and give the connectors a quick wipe down with some rubbing alcohol and a small cloth.
3. See if you can borrow a stick of memory from a buddy and run a test with theirs instead.
4. If that does the trick, start swapping your own sticks in one by one until you figure out which specific one is acting up.

Just wanted to give you guys a quick heads-up that everything is totally sorted! My motherboard fried on me, so I just went out and picked up a new one, migrated all my data over, and now everything is running perfectly. Seriously, thanks again for all the help.