Re: PR1ME C compiler sources

On Thu, 26 Sep 2019 11:53:20 +0100, "Derek M. Jones"
<derek@_NOSPAM_knosof.co.uk> wrote:


>John,
>
>> [The Prime machines suffered from having too many versions of
>> everything. Page 41 of that quick reference card has a 48 bit pointer
>> format with a bit number in the low 16 bits. It seems unlikely that a
>> C compiler would use that as a general pointer format since it doesn't
>> fit in any sort of normal int, and it's not what you'd want to point
>> at an int or a function or anything bigger than a char. -John]
>
>Some Cray machines and DSP chips have a similar problem with using
>word addressing.
>
>Several solve the problem by defining the word to be the smallest
>addressable unit, making chars 48-bits in the case of some DSPs.


Just curious - what DSPs have 48-bit characters?


I have worked with Analog Devices chips that had 16/32/48 bit words in
internal memory and 32/48 bit words in external memory. Instructions
- and extended floats - were 48 bit, but all other data was either 16
or 32 bit. Due to addressing, an individual character could be a 16 or
32 bit value in internal memory, but had to be a 32-bit value in
external memory. Strings - if you used them - were packed to occupy
as few words as possible, and library string functions (mostly)
expected packed sequences rather than arrays of characters.


George

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