[Simh] VAX Tape Emulation?

[Clem Cole]

s/couple of people/couple of families/
ᐧ

On Thu, Jan 25, 2018 at 8:47 PM, Clem Cole <clemc at ccc.com> wrote:

>
>
> On Thu, Jan 25, 2018 at 7:46 PM, Johnny Billquist <bqt at softjar.se> wrote:
>
>>
>> Domain OS using 1056 bytes? On what systems? I used a lot of DN3000, 4000
>> and 5000 systems, and they used bog standard disk drives with 512 byte
>> sectors. (Interesting systems in some ways, but their windowing system was
>> pretty horrible.)
>
>
> ​All of the early ones -- until the DN10000 I'm pretty sure.   They used a
> 1024 basic block, but Mike Spourer had used the Xerox Alto trick of putting
> some of the FS metadata into the controller microcode. That's what the
> extra 32 bytes were.   Masscomp and Apollo used the same SMS 'OMPTI 7000'
> controller for the ST506/ESDI drives, and you'll see it in the
> SMS marketing literature as it says something like "Supports 512/1024/1056
> block sizes".  I have controller doc somewhere in my basement - thinking
> about it, SMS might have even supported blocks as large as 4K - but I
> definitely remember them putting the 1056 stuff in for Apollo.   Remember
> we all knew each other, the firms were one town apart and couple of people
> had somebody working at each.
>
> Anyway, with the DN10000, Apollo started to use the Xylogics 4xx
> controllers and Xylogics either wanted too much money for custom microcode
> or the Apollo guys decided custom microcode was too expensive.   In our
> Stellar days, we used to kid Mike about the 1056 bytes choice. BTW, Mike
> might have done the same thing at Prime, I never looked at/knew much the
> low level I/O of those systems. [@Stellar we used 4096 as the basic size
> but that was a multiple of 512 so it was never an issue].
>
> I've lost track of Mike, but Scott Baden (who is now a Prof at UCSD) was a
> CPU guy on Prime 750 and I'm still pretty close too, and he might know.
> I'll ask him if he remembers next time I see him.
>
> Clem
> ᐧ
>
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