14

I have a 64bit host with 64 bit host OS. I want to install a virtual machine (with 1GB ram or less), but I don't know which will show better performance. I've heard that the only advantage of 64 bit hardware/software is that it can address more than 2 GB memory per process and it's actually slower than 32 bit.

So is it better to install 32 bit guest vm/os or 64 bit.

I think that software I'll run on it is 32 bit, so it'll run /not in emulation/ using 32 bit libraries anyway. But what if I had the 64 bit version of the software?

NickSoft
  • 3,215
  • 5
  • 27
  • 48

1 Answers1

3

Well, like so often you heard hogwash. It has the big advantage of not only supporting more than 2gb per process, but also more than 2b TOGETHER - which is the harder limit. In fact, running a 2gb process on a 32 bit machine leaves little wiggle room for file caches, while running a 2g process on a 64 bit machine leaves tons of.

Unless the system is very little stressed, the memory barrier makes 32 bit OS level wise just a bad install. Heck, I write that on a virtual machine running visual studio - with 8gb memory because it really helps debugging large stuff.

I think that software I'll run on it is 32 bit, so it'll run in emulation

Ah - now you spread bad things, too. No emulation, 32 bit execution is on all decent processors 8not ccounting in Itanium) as fast as 64 bit.

But what if I had the 64 bit version of the software?

Depends. For most software it makes no sense. Depends whether teh softawre can / makes use of more than 2gb memory. But even if not - the OS may.

Keith Reynolds
  • 833
  • 6
  • 12
TomTom
  • 61,059
  • 10
  • 88
  • 148
  • well yes. it's not exactly emulation. just uses 32bit versions of the libraries. however I did not understand which is better. I menioned that virtual machine will have 1GB RAM at most, so memory advantage of 64 bit does no good. I'm only interested in better performance - will 64 bit os be slower because of the 64 bit pointers/memory management etc. – NickSoft Dec 09 '11 at 16:08
  • @NickSoft as TomTom said above a bit more verbosely, the bit-ness (32bit vs 64bit) has no relation to the speed of execution of the instructions. If you have an application that never accesses memory beyond 32bit, and it is compiled for 64bit execution there will be no inate speed difference in execution just because of the bitness of the system. There may be other optimizations done to the software that could improve performance but that is not directly attributable to whether 32 or 64 bit. – Bueller Dec 09 '11 at 16:15
  • So there is no any difference if I'll install 32 or 64 bit os and 64 bit pointers are read/write with the same number of clock cycles as 32 bit pointers? What about vmware emulation - is there a difference. – NickSoft Dec 09 '11 at 17:49
  • No, they are slower - but that is not emulation, and not vmware emulation, is that they are twice as big so they use twice as much memory bandwidth. COmmon sense etc, you know. Still , going with 32 bit OS is gross neglect these days in most cases. – TomTom Dec 09 '11 at 18:47