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From: R Daneel Olivaw <Danni@hyperspace.vogon.gov.invalid>
Newsgroups: comp.sys.unisys
Subject: Re: 1100 Multiply and Divide Fractional Instructions
Date: Mon, 9 Mar 2026 19:47:32 +0100
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Stephen Boyd wrote:
> On 2/23/26 15:27, R Daneel Olivaw wrote:
>> Stephen Boyd wrote:
>>> On 2/23/26 12:22, R Daneel Olivaw wrote:
>>>>
>>>> Look at the code FTN generates when converting REAL to INTEGER (or 
>>>> vice versa), it makes use of something along those lines.  You can 
>>>> then check the equivalent for Double Precision.
>>>> I had to do this for a piece of MASM coding around 41 years ago so 
>>>> my memory of the exact code generated is more than sketchy.
>>>
>>> Ah! I can kind of see where that would be useful in that situation. 
>>> Not being a mathematician I would have to do some serious thinking to 
>>> completely wrap my head around it.
>>>
>>> Whenever I have to convert between floating point and integer or vice 
>>> versa I usually end up doing a bunch of floating point arithmetic to 
>>> make it happen. I can see where being able to use integer 
>>> instructions would be a lot faster.
>>>
>>> Thanks
>>>
>>
>> Well I cheated back then - "FTN has to do it and whatever it does will 
>> be bombproof, so @FTN,L (on a tiny subroutine) is the way to go".
>> My comment in the MASM routine became legendary, "I don't know why 
>> this works but it does so leave it alone".
> 
> I found another use for MF. Converting Fieldata to binary. Like the 
> Fortran code mentioned above I don't really know why this works but I 
> tried it and it does.
> 
> Convert the 6 fieldata numerals in A0 to binary in A1.
> 
>          AND     A0,(0171717171717).   STRIP OFF 'ZONE' BITS
>          AND     A1,(-0,0,-0,0,-0,0).  EXTRACT ALTERNATE DIGITS
>          MF      A2,(54*/29).
>          AN      A1,A2.                3 PAIRS OF DIGITS CONVERTED
>          AND     A1,(0,-0,0).
>          MF      A2,((1*/12-100)*/23).
>          AN      A1,A2.                RIGHT 4 DIGITS NOW DONE
>          AND     A1,(-0,0,0).
>          MF      A2,((1*/24-10000)*/11).
>          AN      A1,A2.                DONE. RESULT IN A1, ORIGINAL IN A0.
> 
> I found this at http://fourmilab.org/documents/univac/cute-tricks.html
> 
> Steve B

That link is bad, it's cute_tricks and not cute-tricks.  Oh, and https.
Some of those tricks are really outdated - 13, 14 and 19 in particular 
(19 assumes non-write-protected I-Banks).  Ascii versions of some of the 
others would be useful.