My iMac G3 RAM upgrade not working

Hi,
I have just tried upgrading my Flower Power 500 MHz iMac G3 from 256 mb ram to 512 mb. But it just makes a ding and does not boot up. the ram I got is 512MB PC133 RAM from PC memory 512MB PC133 RAM (major brand)- microdirect.co.uk
I have tried with just it in only and it with a 128 mb stick.
The only thing I can see is that it is double sided, and the sticks that were in it are single sided (does that matter?).

Any Ideas please?

It's possible the RAM is a higher density than your iMac will support, or maybe has the wrong CAS latency. But try re-seating it a few times and make sure there isn't dust buildup or anything in the slots.

How do I check its density and CAS latency?

Your web link doesn't help unfortunately, and from the price you paid I'd suggest to you that the RAM you've bought is unsuitable for your Mac. Sure, some generic (major brand) PC memory will work in a Mac, but you're far better off sourcing Mac-specific RAM. I'm almost sure the RAM for your model of iMac should be low density. See the specs at lowendmac.com 500 MHz iMac (Mid 2001) Specs or Apple iMac (Early 2001): Technical Specifications. [Strangely, every site about the G3 iMac I've checked does not mention RAM density, or single-sided or double-sided.]

OWC is still, in the opinion of many, to be the best place to shop for Mac-friendly components. Is there a problem for you importing RAM into the UK?

Once again, here are the details of your iMac but it doesn't provide answers to your questions iMac (Early 2001 at OtherWorldComputing.com)
and 512MB PC100 CL2 168 Pin SDRam 2-2-2 fo... (OWC100SD512328) at OWC.

There are ways to find the nearest Mac shop with a Google search using Mac UK, eg. Memory Apple Mac Parts and Repairs from VIS Ltd

This is the specifications of the memory you need:-

Memory for Apple iMac G3 350MHz, 400MHz, 500MHz, 600MHz, and 700MHz models at OtherWorldComputing.com

Most PCs use cheaper high density memory and Apple Macs, particularly G3 and G4's must use low density modules. No doubt the ones you purchased are high density and either the machine cannot boot from it, or it will cause what ios known as a kernel panic attack.

Suggest you buy memory from an Apple source, not Apple branded which is heavy man heavy.

OWC are Mac specialists who have lifetime warranty on memory and are the cheapest, even for us down under.

Also this might clear things up a little about high and low density memory:-

eBay Guides - Myth Low Density vs High Density memory modules

I bought a G4 iBook and a Mac Mini and upgraded the memory of both with Crucial RAM...

on their UK website, they have a gizmo that checks your machine, sees what you have and suggests how to boost the RAM...

RAM Memory Upgrade: Dell, Mac, Apple, HP, Compaq. USB drives, flash cards, SSD at Crucial.com

Check them out... they're fast and guaranteed to work... not as cheap as PC memory but cheaper than Apple memory...

I can highly recommend them...