I've been thinking about memory. I'm a software weenie, so if I've
seriously mis-understood, please *gently* correct me.
Some folks have pointed out that since this is a RISC CPU, then the
executables will be significantly larger (40% was the number I read).
This implies that 8Mb of RAM really is not sufficient. The next logical
memory size is 16Mb (you could go to 12Mb, but that makes 2-way interleaving
impossible I believe). To take full advantage of 2-way interleaving though,
you need two banks, which therefore implies 16 1Mb SIMMs.
This has the nice feature of being expandable to 32Mb, 40Mb, and 64Mb.
(Since any bank of 8 could be upgraded to 4Mb SIMMs. Upgrading a single
bank of 4 would eliminate the 2-way interleave capability, right?)
BUT, it requires all that expensive 4-, 6-, or 8- layer M/B real estate.
Plus drill holes through all those layers is not a pleasant thought (routing
headaches, reliability, cost). And 16 SIMM sockets ($).
Since Waldorf has (seems to have) agreed to produce boards that have surface
mount components, would it be reasonable to mount discrete memory chips
on the M/B? Here was what I was considering:
18 1Mbx4 70ns (is 70ns fast enough?) surface mount DRAMs on the M/B.
(18 because I assume the 3730 part wants parity bits)
8 standard SIMMs on M/B
This way every board has 8Mb to start with. This is enough for a bare-bones
no X11 system (or one that swaps alot :-). One can easily add an additional
8Mb to make a 16Mb system. Or add 32Mb to make a 40Mb system. Or give up
2-way interleaving (if that's possible) and make a 12Mb, 24Mb, or 28Mb system.
- Will the 18 components in small surface mount packages use less
real estate than 8 SIMM sockets?
- How does mounting 18 discretes compare with 8 SIMM sockets cost-wise?
(PWB fabrication has fewer holes, but board stuffer has more stuffing).
- If one makes as few as 56 boards you break the 1000's in the DRAM count
(which gets you to the first cost break). But cost-wise how does this
compare to SIMMs?
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