[Info-vax] For sale: VAXstation 4000/90 128MB Fully Working and Tested

[Arne Vajhøj]

On 7/2/2022 8:34 AM, Bill Gunshannon wrote:
> On 7/1/22 20:56, Arne Vajhøj wrote:
>> On 7/1/2022 6:50 PM, Bill Gunshannon wrote:
>>>                                                 How many shrinks
>>> to increase speed?  How many new peripherals were made available?
>>> We didn't even get decent network cards or even disk controllers for
>>> things like SCSI except from third parties.  Trust me, people using
>>> PDP-11's could see the writing on the wall.
>>
>> Both end customers, ISV's and DEC could see the writing on
>> the wall - 16 bit did not have a future.
> 
> And when they same customers saw the same for 32 bit?  Did Intel
> throw out the X-86 architecture  or make it fit the 64 bit world?
> Granted, Intel almost missed the boat and might have if AMD hadn't
> come along.  Why could there not be a 32 bit PDP-11?  Why did they
> need a totally new and totally incompatible processor?

I don't think "totally incompatible" is an accurate description.

The VAX 7x0 had PDP-11 compatibility mode.

But overall yes: Intel and Microsoft did a far better job
than DEC at the 16->32->64 bit migration.

>> Everybody (read: most) wanted first 32 bit and later 64 bit.
> 
> And I still don't see what part of the PDP-11 basic architecture
> made them not be extensible to that.  The PDP-11 architecture was
> by far one of the best I have worked with and my experience goes
> all the way back to the 8080 and 6800.

You can't really extend from X bit to Y bit. You can create
a CPU with X and Y modes and an OS that supports both X and Y modes
in a more or less elegant way.

Arne