[ih] "network unix"

[Jack Haverty]

Opcode 7002.  From Wikipedia:

7002 – BSW – Byte Swap 6-bit "bytes" (PDP 8/e and up)

/Jack

On 10/09/2016 03:12 PM, Brian E Carpenter wrote:
> I don't recall a 6-bit byte notion in the PDP-8. The smallest addressable unit
> was the 12-bit word, and the primary I/O device was an 8-bit ASR33 (which read
> into bits 4 through 11 of the 12-bit accumulator, the 1966 manual reminds me).
> Of course you could squeeze upper case ASCII down to 6 bits and store two
> characters per word to save core memory; I expect I did that but this was 1969
> so I don't quite remember.  Unlike some of my cohort, I didn't pad out my
> dissertation by including source code, so it's long lost.
> 
> Regards
>    Brian
> 
> On 10/10/2016 08:57, Jack Haverty wrote:
>> Wow, people are actually reading this stuff...   Thanks to everyone who
>> pointed out that PDP-8s didn't have 8-bit byte.  Tough audience...
>>
>> What I meant to say was "PDP-8s had 12-bit words and IIRC some notion of
>> 6-bit bytes.  PDP-11s had 8-bit bytes in 16-bit words"
>>
>> Somewhere between brain and fingers my neural network must have dropped
>> a packet......
>>
>> /Jack
>>
>>
>> On 10/09/2016 12:20 PM, Scott O. Bradner wrote:
>>>
>>>> On Oct 9, 2016, at 2:36 PM, Jack Haverty <jack at 3kitty.org> wrote:
>>>>
>>>> Hi Noel,
>>>>
>>>> You're right, I should have said 32KW....but I wonder how many people
>>>> today would know what "KW" means?  I suspect many would think it
>>>> referred to the power that our ancient monsters consumed...actually
>>>> probably not far off for the bigger machines that consumed many square
>>>> feet of lab space!
>>>>
>>>> The other aspect of the "Stone Age" that may not be remembered today is
>>>> that a "byte" was not yet very well-defined back then.  PDP-8s had 8-bit
>>>> bytes in 16-bit words.  
>>>
>>>
>>> PDP-8s were 12 bit words
>>>
>>> PDP-1, 7, 9, 15 were 18 bit words
>>>
>>> PDP-11 were 16 bit words
>>>
>>> PDD 6, 10 were 36 bit words
>>>
>>> Scott
>>>
>>>> Other machines made different choices.  The
>>>> PDP-10 was agnostic -- the instruction set allowed the programmer to
>>>> specify whatever byte size they liked.  So a "byte" only made sense in
>>>> the context of a specific machine.
>>>>
>>>> Today of course we all know that a byte is 8 bits.  Period.  Perhaps
>>>> some historian can figure out exactly when that happened.....
>>>>
>>>> Fun times...
>>>> /Jack
>>>>
>>>> On 10/09/2016 10:21 AM, Noel Chiappa wrote:
>>>>> A few notes/corrections:
>>>>>
>>>>>> The /40 design utilized a single address space for instructions and
>>>>>> data, so everything had to fit in 32KB of memory (yes K, not M or G).
>>>>>
>>>>> Err, that was 32KW, i.e. 64KB. But 8KB was the I/O page (device registers), so
>>>>> only 56KB of memory - sort of, because V6 Unix used one 8KB page to map in
>>>>> each process' kernel stack + other swappable per-process data, so really only
>>>>> 48KB for all kernel code, data, disk buffers, etc.
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