13 Feb
2014
13 Feb
'14
12:19 p.m.
On Wed, Feb 12, 2014 at 02:14:26PM -0800, Fred Cisin wrote:
On Wed, 12 Feb 2014, tom wrote:
[SEVEN levels of untrimmed quotes deleted]
It's obviously megabytes. You can get 768GB in a PC these days, but that's not
really the kind of hardware that one has lying about running primitive versions
of Windows[0].
I have more than 512 GB RAM on mine. 768 GB. No
Complaints. 98SE might not
use it all, but no complaints. You don't have to but 3 GB RAM in it just
because it can handle it. I originally had 256 GB RAM in it and 98SE ran
well.
Did you mean MB or GB??!?
You really have 3/4 of a TERABYTE on a Windoze98 machine? I had always heard that most of those machines could
not comprehend more than
4 GigaByte (32? address bits), and that Windoze98 couldn't tolerate more than
HALF a Gigabyte.
I've just experimented with that Windows 95 VM. Reputedly, because of design
flaws in its memory allocator, it starts bogging down beyond 512MB of RAM, and
won't boot at all with too much. My tests show it boots with 800MB but not with
960MB.
Do remember that the amount of memory supported in a system depends on the size
of the physical and virtual address spaces. The virtual address space
corresponds to the size of a pointer, and the physical address space
corresponds to the number of pins actually coming out of the CPU package.
Paging hardware allows the physical address space to be larger than virtual.
On 32 bit x86, pointers are 32 bit, giving a 4GB virtual address limit. This
generally means a limit of 2-3GB per process, depending on how the OS is
designed. Depending on CPU model, physical address space -- the amount of RAM
you can install (less space for ROMs, MMIO, etc) -- is anything from the same
32 bits (e.g. the 80386) using classic paging, up to an architecture limit of
48 bits (256EB) on current x86-64 chips using PAE, although chips you can
currently *buy* appear to be limited to 4TB on the top-end, and 32GB on stuff
us mere mortals can afford.
The same kind of limits apply to other architectures: ARM has 32 bit pointers
but LPAE provides up to 48 bit addresses again.
Back to the toy operating systems, and they're deliberately hobbled to 32 bit
physical addresses too. If you want more than 3GB of RAM in Windows, you have
to upgrade to 64 bits. Why not upgrade to a proper computer instead?
[0] Of course, all versions of Windows are primitive *rimshot*