Modifying microcode

[allison]

On 06/01/2018 02:46 PM, Antonio Carlini via cctech wrote:
> On 01/06/18 18:40, Eric Smith via cctalk wrote:
>> On Fri, Jun 1, 2018 at 11:08 AM, Robert Armstrong <bob at jfcl.com> wrote:
>>
>>>> Eric Smith <spacewar at gmail.com> wrote:
>>>> The control stores of the 11/785, 8600, and 8650 were entirely WCS.
>>>>
>>>> All other VAXen had (relatively) large ROM control store and tiny
>>>> WCS or
>>>> patch store.
>>>    You forgot the 11/730 and 725.  The KA730 used 2901 bit slicers
>>> and the
>>> control store was entirely in RAM.  After power on it was a paperweight
>>> until the 8085 CFE loaded the microcode.
>>
>> Thanks for the correction! I've never used those models.
>>
>
> In the Digital Technical Journal #2 (the one that describes the
> development of the MicroVAX II)
>
> they say that they used the VAX-11/730 as a testbed
>
> the 78032 chip. The VAX-11/730 was chosen because it was "an entirely
> 'soft' machine".
>
>
> (The VAX-11/725 is essentially the same hardware but in different
> packaging).
>
>
> Antonio
>
>
It was my understanding from using the 730 that there was limited
(really limited) microcode
enough to load the WCS as the tu58 was a serial device (standard tu58)
and the 730 had to
unpack and stuff the WCS.  You need little to do that but far from even
PDP11 instruction set.
The Microcode was loaded was the "what made it a VAX stuff".

Allison