Date: Mon, 28 Jul 2003 17:45:52 -0400 From: Stephen Kenda <[EMAIL PROTECTED]>
I was talking to someone who is selling a powermac 8500 and was surprised to hear
that it had two 256 mb ram dimms in it. I did not know you could use 256 mb
ram dimms in these pci powermacs.
Has anyone had any direct experience with 256 mb ram dimms in PCI-powermacs?
If so, I'd like to hear about it. In particular i'd appreciate any info that would be
important to find out about this ram before further entertaining the idea of
purchasing a pci-powermac so-equipped.
The Apple Hardware Developer Notes for the 7200 ("PPC_7200.pdf") says that the 7200 can use 256 MB DIMMs. That's not very relevant as it is a different machine. However, the architecture of the 7200 is about as close to the x500 machines as it can get and still be different.
The Apple Hardware Developer Notes for the 7500 & 8500 ("PPC_7500_8500.pdf") clearly states that 128 MB DIMMs are the largest supported. However, a geeky reading of the "RAM Address Multiplexing" section implies that they too (in addition to the 7200) should support properly built 256 MB DIMMs. The DIMMs would need to be built with some very specific parts so that the DIMM would have an addressing configuration (number of row and column address bits) which the machine supported.
It wouldn't be the first time that Apple's notes report a smaller memory module size than is actually supported as maximum.
All that said, I've never heard of, nor seen a 256 MB DIMM for these machines. It was my impression that nobody ever made one. If this guy does have some, it would be very interesting to investigate and determine the source and/or brand. Such DIMMs would allow one to take all the x500 machines and related clones up to 1.5 GB of RAM. The Hammerhead supports 1.5 GB of RAM, but most machines only have the eight slots and you need twelve with 128 MB DIMMs to get 1.5 GB of RAM.
However, my guess is that while they could be 256 MB DIMMs in theory, the seller is probably just confused or mistaken.
Jeff Walther
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