32 bit and 64 bit executables

[Andrea Pagani]

When system HW has more than 4 GByte of RAM, is it necessary to provide an executable linked with a different option (PA-RISC 2.x) in order to address all system RAM addresses or is only the addressable memory that the process uses that needs a 64 bit architecture?

[Wodisch]

Hello Andrea,

even on a 64bit HP-UX system will a 32bit
codefile NOT be able to address more than
3.75GB...

All 64bit processors are PA-RISC2 - so you
will want to have only those ;-)

HTH,
Wodisch

[Michael Tully]

Hi,

32 bit has a limitation off 3.75Gb, however
a tool called Memory Windows which *may* be
able to help you. Have a look at the link to this document.

http://www.docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B3920-90091/B3920-90091_top.html&con=/hpux/onlinedocs/B3920-90091/00/00/63-con.html&toc=/hpux/onlinedocs/B3920-90091/00/00/63-toc.html&searchterms=memory%7cwindows&queryid=20010926-233830

HTH
-Michael

[Stefan Farrelly]

Life will be a lot lot easier if you can compile your programs as 64bit (+DA2.0W) so you can address as much memory as you need. If you use 32bit you are going to have lots more difficulty configuring memory windows, setting bits on the binary (chatr) etc.

[Andrea Pagani]

As I understand, I wouldn't have problem running 32bit executable on a server having, for example, 8 GByte of RAM, unless this executable would require a shared memory space greater than 1,75 GByte. Only in this case I'd have to compile my exe using the 64bit option otherwise I'd have to use memory windows. Is it correct?

[Stefan Farrelly · Accepted solution]

Your last post was correct. It doenst just apply to shared memory though, even data space for your executable must be less than 2 GB as a 32bit program simply cant adress it, without recompiling it to 64bit.

[Wodisch]

Hello Andrea,

in addition to Stefan's reply: on HP-UX 11.11
(or 11i) the limit (with SHMEM_MAGIC/_EXEC
tricks) is about up to 3GB per 32bit process...
at least AFAIK...

Just my ?0.0,2
Wodisch