Hi Annick,

On 08 Sep 2014, at 09:26, Annick Fron <list@afceurope.com> wrote:

> What is the difference between pharoS and pharo ?
> Annick

At one point there was just the standard Squeak VM. Then Eliot started the CogVM project, whose ultimate goal was to have a JIT compiler. That meant that he had to change part the way the image interacted with the VM, especially around stack and closure/block usage [this is not 100% accurate, but the details are complex]. So he decided to tackle this in two broad steps: first make the just mentioned changes, test that part and then do the JIT part.

So the Pharo S (aka Stack) VM and the Pharo (COG/JIT) VM are brothers, with the old Squeak VM being their ancestor.

Practically, the S VM is slower (because it does not do JIT compilation), but much more portable (because it does not have to generate machine code). The S VM is often used to decided whether a VM problem is JIT related or not.

HTH,

Sven