pha@caen.engin.umich.edu (Paul H. Anderson) (08/07/90)
With RAM costing something like $80/megabyte, an application that requires 4.5 gigabytes of data could be kept in RAM for less than $500,000 or so. Does anyone know of current platforms that support very large RAM capacities on the order of 5-8 gigabytes? Ideally, this would be program accessible RAM, rather than in solid state disk drives. I'm looking for things that can be purchased in the next 6 months. Please reply to me directly: pha@caen.engin.umich.edu I'll summarize any answers to the net, if anyone is interested. Thanks! Paul Anderson CAEN Systems Programmer University of Michigan (313)-936-1355
mo@messy.bellcore.com (Michael O'Dell) (08/07/90)
Hmmm..... The last time I checked 32 bits of address would only get you 4 gigabytes, minus whatever the OS wanted out of the user virtual space, since most Unix systems put the kernel in the uppermost or lowermost part of shared virtual space. I guess on a 386 or an RS/6000 you might do a bit more, but if you compute how much POWER that large a RAM array would consume (and how warm it will make your office!) you will discover why no workstation has that much memory on it. Not to mention that when you get that many ram chips going, you really need to start doing 3-Detect/2-Correct memory ECC, rather than the 2-Detect/1-Correct that many (but certainly not all!!!!) systems do. I believe the large IBM mainframes do 3D/2C already, and the folks with Big Bucks anxiously wanting to buy such machines will tell you quickly they agree with the need to do that, lest your Mean-time-between-uncorrectable-memory-error be come unacceptable. And as for the price of memory making this attractive, the price of the ram chips doesn't begin to represent the entire memory subsystem costs, even if it is substantial. -Mike
rcd@ico.isc.com (Dick Dunn) (08/07/90)
mo@messy.bellcore.com (Michael O'Dell) writes: > The last time I checked 32 bits of address would only get you > 4 gigabytes, minus whatever the OS wanted... ... >...I guess on a 386 or an RS/6000 you might do a bit more,... Careful...don't slip on the difference between physical and logical. The 386 has an effective virtual address space > 32 bits (if anyone is so foolish as to use the &^%$#! segment registers), but a 32-bit physical address, as in 32 address-select pins. -- Dick Dunn rcd@ico.isc.com -or- ico!rcd Boulder, CO (303)449-2870 ...Are you making this up as you go along?