problem with yikes powermac

hey, im very new to apple so bare with me, some friends had two G4 powermacs that both needed help, i decided id love to learn something new so im giving it a shot,
the one im using right now is a yikes i beleive. its a G4 400 with PCI graphics,

the problem im having is no matter what ram i install, it shows half. if i install a 512Mb dimm it comes up 256, 3 512's they all come up 256 for a total of 768. if i install two 256's they each come up 128 for a total of 256. its the wierdest thing ive ever seen but maybe normal on this kind of machine?

the second G4 i havent really touched yet. its a dual 450 gigabit which i need to hunt down a power supply for. and probably ram

ill be running tiger on both

Certain old Power Macs (particularly the B&W G3 and Yikes! G4, which are essentially the same thing) can only use low-density RAM. The largest modules they can use are 256 MB.

The only 256 MB modules that can be used in that computer have the RAM chips on both sides of the module. That means each chip has 16 MB of RAM on it (16 MB x 8 chips per side x 2 sides = 256 MB). That's the most any B&W G3 or Yikes! G4 can see per chip. So single-sided 256 MB modules or any 512 MB modules will not work.

I know that Sawtooth Power Macs can use 512 MB modules and single-sided 256 MB modules.

ooh. is there anything that can happen by using single sided 256 or 512Mb dimms in it, like crashing? or do you simply only see half or less of the ram?

forgot to ask, when i get the gigabit dual 450 running i dont know what to expect, will it be much faster then the yikes 400?

Only marginally faster, say 10% for processor speed and 10% for AGP graphics. and you do need double sided RAM otherwise a 512MB module will show up as 256MB, but you have already learnt that.

Keep away from high density PC RAM as that will make it crash with a kernel panic attack, asking for re-start in multiple languages.

Both the Yikes and the Gigabit Ethernet 450MHz DP, which will be much faster, require PC100 memory modules. You can use PC133 but these will operate at 100MHz bus speed.

Many older machines would not work with a 512 Meg memory module. Some early P3 boards I worked with only took 256 Meg Dimms in each slot. The Sawtooth and Gigabit Ethernet will take 512 Meg modules as long as they do not use high density Ram Chips. I have a 500 Mhz Sawtooth with 2GB RAM and it works great.

The Dual 450 especially with applications that use the Dual CPU's will be quite a bit faster than the Yikes. The Yikes is basically a G3 Blue and White board with a G4 CPU.