On Sunday, August 5, 2001, at 03:38 AM, Karl Ramberg wrote:
>
> Ross Boylan wrote:
>>
>> On Sat, Aug 04, 2001 at 12:56:30AM -0400, Doug Way wrote:
>>>
>>> With the VM, usually the only important thing is that your VM version
>>> should be the same as or more recent than the image version. (not
>>> earlier)
>>
>> I thought I recall roughly the reverse rule: the definition of a major
>> version (e.g., 3 in squeak 3.1) is that a VM of that number will work
>> with all images of that era, even if they have a higher minor
>> version.  So VM version <= image version, rather than the reverse.

I don't think that major version definition is true anymore (not sure if 
it was ever true).  There wasn't a major VM change from 2.x to 3.x as 
far as I'm aware.  It is true that the .sources file changes with the 
major version, though... Squeak 2.x uses the SqueakV2.sources file, 
Squeak 3.x uses the SqueakV3.sources file, etc.

>> Put slightly differently, if a new VM is required, the major version
>> number gets bumped.
>>
>> Perhaps the different statements are all true, provided one interprets
>> version to mean major or minor appropriately.
>>
>> This is of some practical interest to me, since I'm running 3.0 VMs
>> against 3.1 images.
>
> The VM is bacward compatible, the image is not. So a 3.1 image will not
> work with a 2.7 VM but a 2.7 image will work with a 3.1 VM. Keep your
> VM up to date if you follow the path of the ninja -> 3.1alpha!

Karl has it right.  (Although I guess I'm also using a 3.0VM with a 
3.1alpha image, but they're not all that incompatible yet, except for 
the Balloon3D issue which I don't currently care about.)

- Doug Way
   dway at riskmetrics.com