Craddock, Chris wrote:
Radoslaw writes
The memory is not unique design. There are regular DIMMs inside the
book. High quality, ECC, good brand, but still same technology as in
PC.
Memory controllers are probably completely different, but the
"back-end"
(DIMMs) are not.
The PARTS that are used in the box are pretty much the same as other
commodity parts. True enough.
The DESIGN of the way they are put together, the circuitry, EDC/ECC,
page-modes etc. are predicated on the TSO (ie "total store order" not
timesharing option) memory model and the z architecture storage
consistency rules documented in PoPs.
The DESIGN of the z memory subsystem (and caches) is only distantly
related to the memory subsystem design in a commodity PC.
This is matter of meaning. The back-end is almost the same as in PC.
This modules are NOT significantly faster than in regular PC.
Probably "overall memory solution" is faster and more reliable than
bunch of DIMMs - per analogia to disk systems. Single SCSI (or FC) drive
in modern DASD box is the same as in (better) PC. However the disk
system is significantly more reliable (RAID), faster (cache) and more
featured (i.e. remote copy).
From the other hand - is there so huge difference between DIMMs and
zMemory ? Personally I doubt.
AFAIR (I could be wrong) the number of DIMMs suggest the total memory is
simply sum of DIMM capacities. In other words: no "RAID-like" solution,
probably some "cache-like" solution, probably faster and wider memory bus.
Regards
--
Radoslaw Skorupka
Lodz, Poland
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