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

[Bill Gunshannon]

On 7/2/22 06:16, Johnny Billquist wrote:
> On 2022-07-02 00:50, Bill Gunshannon wrote:
>> On 7/1/22 16:02, Arne Vajhøj wrote:
>>> On 7/1/2022 2:31 PM, Bill Gunshannon wrote:
>>>> Was it?  My guess is that the only improvement that might have been
>>>> needed for Dave's application was a faster processor.  And that was
>>>> done even after the death of the PDP-11 in DEC's eyes.
>>>
>>> I don't think PDP-11 not being available was the driver behind the
>>> move to VAX.
>>
>> Not lack of availability at first, but complete stoppage of development
>> played a major role.
> 
> There wasn't. Last release of RSX was in 1999.

That's OS development, not CPU.  BSD for the PDP-11 continues to
develop today as far as I know.

> 
>>> PDP-11 production continue until 1997 when people were migrating
>>> from VAX to Alpha - not to VAX.
>>
>> How much development was done during that period?  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.
> 
> There wasn't much demand for speed increase. 

I don't think there was ever demand for speed increases in any CPU.
But users were always happy to see it.

>                                               But DEC even did offer 
> their own SCSI controller (RQZX1), so it wasn't just third party. You 
> are drawing conclusions from incorrect data.

Was that SCSI developed for the PDP-11 or the MicroVAX and just
happened to work on the PDP-11?  Why did they never release a DSSI
card for the PDP-11? (Actually, I am sure the VAX module would have
worked but I am not aware of any support for it in a PDP-11 OS.)

> 
> The biggest reason for migration from PDP-11 to VAX was because of the 
> larger virtual memory addressing space.

Which could have been developed into the PDP-11 while keeping most of
the good things in the architecture.  I still think it would be fun to
use something like SIMH to build an "improved" PDP-11 just to see where
it could have gone but, alas, I am too far past my prime to actually
do it.

> 
> People really did not (in general) enjoy trying to squeeze ever larger 
> software systems into the tiny addressing space. It was a lot of effort 
> that could be spent elsewhere.

Thus the reason the processor should have seen more development and not
a complete and totally incompatible replacement.

But, at this point that is all water under the bridge.

bill