Half of SDRAM Recognized on G3 (B&W)

I have a 350MHz PowerMac G3 running 10.4 with originally 128MB. I had a stick of PNY 128MB SDRAM sitting in the basement, so I put it in the DIMM1 slot. Now, DIMM0 shows 128MB, type and speed unknown, status OK. But, DIMM1 shows 64MB, type/speed unknown, and status OK. I double checked the module and the sticker clearly reads 128MB. I noticed a significant performance increase, but where's the rest of my memory?

I don't know much about your issue,
except the only thing i can think of is the obvious, your ram is somehow not making your mac happy, just curious, was it out of a PC? Im stabbing in the dark here, but is it non EEC or ECC or whatever that was. I dont know at all, someone else will help you, i just came here to say
UPGRADE RAM!!!
It will make you
SO MUCH HAPPIER WITH YOUR MAC!!! Your Mac should have 4 ram slots, which is great. I wish my Mac had 4 ram slots. It's so much cheaper to max out the ram with more slots. To get your mac flying, you should have at least 512mb to make it decent (Really with 4 slots you should have 768 or 1GB), and ram is VERY cheap these days, i just picked up a stick of 512 for a friend off of ebay for $20.
I'm sure you already know this,
but max the ram!

Max ram=max happiness

Good luck.

Is that PNY PC133 SDRAM by any chance? I have a 128Meg PC133 stick that will not work right in older Macs and older PC's either due to it using Higher Density RAM chips. That was an issue even with some earlier Pentium 3 boards. My stick is Kingston PC133 with HD Chips and it gets me 64 Megs on my G3 B&W and even G4 500 Sawtooth and my Asus CUBX P3 board in my old PC.

It's a PNY from Best Buy I picked up years ago for $20. I actually can't tell if it's PC100 or PC133, it's a mystery stick with "Guaranteed Compatability." Come to think of it, it was in the basement in the first place because it never worked in my old AMD machine. In the meantime, I just ordered 4x128 of 2-2-2 off eBay for a mere $24 and added another 64MB PC100 for an artificially low total of 256. I hardly use Macs, but I'm finally using this old $30 G3 to hook up to my MIDI drums and I'm blown away at how well it runs on 256. Best cheap computer ever - by far.

Compatible with what? You do need low density modules and be aware most RAM sold through eBay etc is high density PC RAM. There is a difference.

Your machine's specs call for a maximum of four PC100 3.3v unbuffered 8-byte non parity 168 pin SDRAM modules. Have a look at the Apple section of eBay and see if any sellers are offering this RAM as Apple compatible