I want to build an old PC with a Geforce 2 Ultra, Pentium 3 @933 Mhz and Win 98SE operating system.
Now my question is, if I put 3 128 MB RAM sticks in there, will it hurt the performance? I know systems back then could not do dual channel, which is why I am thinking I might as well put 3 sticks instead of two (for 384 MB), but will it somehow increase the latency? Or is it better to just have 256 MB of RAM?

PS: I am aware that GOG does not support Windows 98, but if I install the games on my Windows 10 machine and then copy them over they should work from what Ive seen online. I know that some might have more modifications done to them and they may not run, but most should work as the originals, and if they dont I'll just play them on my modern machine. I still think it will be fun to play some on the old PC/

Not really...

If we talking bench marking you will get better results from single big sticks than multiple smaller sticks though.
But more ram is good thing.

you on just 98 or 98se?

@Regals

WIn 98 SE.
It's good if more RAM does not hurt it. I'll be keeping it offline, so I won't install an antivirus either. Always disliked how much antivirus affected performance on old machines.

(Sorry but I can't seem to post replies, the browser just crashes)

If the speed of the new ram is slower, than yes it could hurt performance, namely that all ram I think goes with the slowest ones (I think) since two slots at a time have to have the same timing. I think, it's been a while.

Otherwise I'm not sure what would hurt performance in regards to ram, since having too little pushes more on the Virtual Memory/paging. If you have enough ram you can turn paging off, and for basic applications will be fine.

With regards to games though, I couldn't say. I think I remember Starcraft requested something like 384MB of ram when it starts up, although how much it actively uses I don't know.

In all cases, the OP will see some benefits from having more RAM installed, in the sense that Win98SE will make use of the additional RAM, and that- some games will play better as well. I would even push further and go for 512 MB

If the third RAM module is slower or has a worse latency, then , yes, there might be a slight negative effect as all R5AM modules will have to be aligned on the less performing one. But it's hard to see it as important enough to balance the benefit of having more RAM.

It won't make a huge difference on systems that old, as long as the RAM modules have the same specifications (in compliance with the chipset used of course).

If you have it, may as well use it, but you won't notice any difference between 384 and 256.

From memory (get it?), 98SE has a bug if you use more than 512, but there is a workaround available.

In general, no it shouldn't. There are some cases where it could though, such as a system that can take a certain amount of RAM, but the tag RAM chips don't handle the entire addressing range the system supports which if memory serves correct caused portions of upper memory to not get cached in the L2 cache. It has been eons since that was a problem in PCs though and I don't know anyone who ever put that much RAM into such an old PC to be affected by the problem, although it's more likely one might hit the issue building an old PC with lots of hand-me-down parts collected over the years where one could have amassed large quantities of ancient RAM. :)

If possible, try to hunt down the manual for the motherboard as it will tell you how much RAM the tag RAM covers. Going over that amount might reduce performance although it may or may not be noticeable depending on various factors.

Well, my last Win 98 SE PC had the following specs:

Athlon XP 3000+
1 GB RAM
Geforce 7800 with 512 MB VRAM (AGP version)
Creative Soundblaster (can`t exactly remember model)

So I would recommend 1 GB of RAM.

There are a few cases where more RAM could cause issues:

1. Older OSes might not handle too much RAM. Windows 95, I believe, will not boot with more than 496 MB or so of RAM; Windows 98 apparently fails to boot around 1.5 GB of ram.

2. I remember reading about a motherboard that would only cache the first 64 MB (or so) of RAM. Hence, adding any more RAM will slow down the computer drastically, as the OS isn't aware that some of the RAM is really slow.

The workaround, in both cases, is to send the OS kernel a boot parameter to tell it to only use a certain amount of RAM.

Incidentally, on Linux there is a driver ("slram" or the more recent "phram") that can allow you to use the unused memory as a virtual disk, allowing you to put swap space there.

Google the chipset. You should be able to find out how much memory is cacheable. I want to say with a P3 you should be fine.

As others said, a P3 with Win98SE could have 1GB ram. So you're fine and I would even suggest to increase your memory to at least 512 MB. Any specific reason you want to use 3 sticks and not 2 or 4?

As regals said, at the same total RAM, fewer big sticks give you more performance than many small. I.e. it's better to have two 256 MB modules that four 128 MB modules.

Most important however: take care that all the modules are identical. If you mix modules with different latency, or different single size, you can run into problems. There could even be compatibility problems with modules of different manufacturers, even if they had the same specified latency.

With a Pentium 3 machine you should be fine with any amount of RAM the chipset can handle. Depending on the chipset and mainboard configuration this can be up to 512 MB or on some chipsets even more. For playing typical games of that era on a Pentium 3 machine, 512 MB of RAM should be more than enough, so don't bother with anything above that.
Those with a 512 MB limit can usually handle modules with a maximum of 128 MB per module. While it is possible to use 256 MB modules in such machines, they will only be recognized as 128 MB modules.
On older platforms it was actually possible to have too much RAM installed. Chipsets for Socket 5 and 7 CPUs often allowed to install 128 MB of RAM, while only being able to cache 64 MB. Using more than those 64 MB would hurt the performance on such machines. Since the entire cache is part of the CPU on a Pentium 3 (unlike those older CPU generations mentioned before), the chipset does not matter here.