Re: Quick Memory question

On Friday 2005-02-25 22:13, June Tate wrote:
> On Feb 25, 2005, at 8:20 PM, Trent Shipley wrote:
> > On Friday 2005-02-25 16:41, Joseph Sinclair wrote:

> Even if you're running in a flat memory space (like several operating
> systems, games, and demos do) you _still_ have at least one bit of that
> 32 bit address that is chopped off for the selector (in technical
> terms, the selector refers to the entire memory space). So, you're
> limited to the 4GB address space, unfortunately.

OK. I still do not get it.

Usually when something was programmed in C, and I have 2 gig of something it
is because they used a signed integer and threw away the bit patterns
representing negative numbers (effectively wasting a bit). I regard this as
slightly sloppy programming like forgetting to dot an "i".

Of course, you can get the same result if you have a 32 bit word (in ANSI/ISO
C you would use an unsigned integer) then stole a bit to use as some sort of
flag in a bitmask. No matter what, 2^32 is 4 gig and 2^31 is 2 gig.

If 32 bit Intel chips use one bit for a "selector" what are they selecting and
how can they have the selector and still address 2^32 memory locations? If a
32 bit Intel CPU can index 2^32 *RAM locations why can the same 32 bit Intel
chip address only 2^31 virtual memory locations?

Also, my other question was not answered.

Can I configure a machine with a 32-bit Intel architecture to use:
2^32 *RAM as main memory
and use
2^31 *RAM as virtual memory by treating the additional 2^31 *RAM as a
(virtual) RAM drive. (This is based on a view of memory as a type of storage
and all storage as cache: ALL IS CACHE. It is just a matter of speed,
density, stability, durability, power use, waste heat, and cost.)

If I replace magnetic VM with *RAM VM, what happens?

How many VM drives are practical?

Alan, should I try to tune the VM manager in newer Linux kernels. Will this
come close to emulating a VERY large array of *RAM in a 64 bit machine?

---------------------------------------------------
PLUG-discuss mailing list - PLUG-discuss@lists.plug.phoenix.az.us
To subscribe, unsubscribe, or to change you mail settings:
http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss