tomcat-users mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Francis GALIEGUE <>
Subject Re: [OT]RE: Maximum memory that can be assigned to Tomcat on windows platform
Date Thu, 01 Dec 2011 11:32:46 GMT
On Thu, Dec 1, 2011 at 12:29, Casper Wandahl Schmidt
<> wrote:
> That didn't quite help me understand, because how can the OS map from ie.
> 0-4GB to 4-8GB (the window is moved) when it can only use a 32bit register
> to tell the machine where to look in the psysical memory, that is where my
> knowledge ends :) So I read about PAE and found out that it uses 2 registers
> (36 bits due to some bits being used as flags) and that makes good sense,
> but how can the cpu calculate an address without overflow and send a command
> to the bus containing a 36bit address (or whatever fetches the bits from
> RAM)? That is where I'm puzzled but I guess it is because I'm not at all
> into ISA-level and below :)

It is the role of the MMU to do that. At any one time, it can map a
"virtual", 32-bit wide, address to a "real", 36-bit wide address. It
uses TLBs (Translation Lookaside Buffers) for that, and it is the OS'
role to have the correct TLB in place at any time.

Francis Galiegue
Ingénieur système
Mob : +33 (0) 683 877 875
Tel : +33 (0) 178 945 552
40 avenue Raymond Poincaré
75116 Paris

To unsubscribe, e-mail:
For additional commands, e-mail:

View raw message