Intel or AMD CPUs

[Beware the talking cat]

Can't a 16 bit system use exactly 2GB ram?

(stupid vista with a 4gb INCLUDING video memory limit)

[Umiman]

Can't a 16 bit system use exactly 2GB ram?

(stupid vista with a 4gb INCLUDING video memory limit)

Pretty sure the RAM limit for XP pro is 3.3gb of RAM since that's the RAM limit for SupCom when running on XP.

[ainsoph9]

That may be so, but I am speaking of the number of addresses possible without anything attached. However, this number may vary depending on whether it is byte or word addressable I do believe. It also depends on the memory type and how the addresses are grouped. The calculations that I gave was simply the maximum based on the assumption that the system was as stripped down as possible without anything weird attached.

[Smidge204]

A 16-bit processor using a 16-bit segment pointer and 16-bit segments can access 4GB of memory.

Even though Intel's 80286 processor had such an arrangement, the designers only gave it a 24-bit address bus. (That was fine, though, since RAM was so ungodly expensive at the time that nobody even imagined using ALL 16MB)

Also, all memory is byte-addressable.
=Smidge=

[ainsoph9]

Smidge204 wrote:

Even though Intel's 80286 processor had such an arrangement, the designers only gave it a 24-bit address bus. (That was fine, though, since RAM was so ungodly expensive at the time that nobody even imagined using ALL 16MB)

Also, all memory is byte-addressable.

Yeah, thankfully RAM came down in price.

As for memory, most memory is byte-addressable nowadays. However, some machines still use word-addressable memory. Seemingly, the industry has come to a consensus on this. It is possible that by using byte-addressable memory they are able to maximize the space allowed without having to use any weird offsets for instructions that have a weird number of bytes that they take. This could also possibly affect the instruction of memory formatting along with some other things.

[onizuka-gto]

hmmm....so a 16-bit cpu can use 4GB of ram?

then how come my 32-bit win xp professional can't use 4GB?

I had to go though the pain that is 64-bit win xp professional to use my 4GB.

kinda pissed me off, cos my monster pc doubles as my gaming rig (not any more though).

On another note, finally finished downloading psychonaut, which was amazing, considering at leased half of 2.84GB was done on my mobile 3G network, and 1/3 of it was while i was on the road.

Wish i got HSPDA (3.5G) but its ungodly expensive.

[ben1234]

32-bit systems can use 4gb but it'll only say you have 3gb.

64-bit systems don't have this problem.

[Smidge204]

Oni:

The 16-bit 80286 microprocessor is, internally, capable of forming a 32-bit address. However the address bus is only 24 bits wide (The top 8 bits are truncated).

Windows can only see ~3GB because... Microsoft sucks.
=Smidge=