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Knowledge Base Forum ... and (up to)80bit FTN95 !

 
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John-Silver



Joined: 30 Jul 2013
Posts: 631

PostPosted: Mon Sep 07, 2015 10:07 am    Post subject: Knowledge Base Forum ... and (up to)80bit FTN95 ! Reply with quote

I have 2 comments here, having just glanced at the forums list and seen something that's not really whacked me in the eyes before.

1. Frstly, it seems that the Knowledge Base was abandoned 4 years ago since that was the last post made on there.
Is it a case of the KB is dead, long live the KB ?
Can I suggest that it might be useful to resuscitate the KB for appropriate (resolved) problemos ?
As (understandably since I realise the effort that might be involved) it doesn't seem likely anytime soon that we'll see any specific documentation on the subjects, and wading through the forums is a bit like swimming in treacle at times , It might be worth re-iterating the oft expressed desireability of new similar forum categories (admin controlled) for topics such as :-
a) useful example codes storage.
b) 'gobledygook' sometimes undecipherableerror messages explanations


2. Now, I started a bit of a trawl (well more like a sweep with a tadpole net actually) of the posts there and I discover that apparently FTN95 used to be ..... 64bit !!! or even quasi 64/80bit ! ... as long ago as 2004 !!!!!!!!!!
Someone's going to have to enlighten me on this one as I thought we were eagerly awaiting the arrival of 64bit.

Here's the article which I'm referring to:-
http://forums.silverfrost.com/viewtopic.php?t=198
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LitusSaxonicum



Joined: 23 Aug 2005
Posts: 1683
Location: Yateley, Hants, UK

PostPosted: Mon Sep 07, 2015 12:27 pm    Post subject: Reply with quote

John,

The 64-bit compiler addresses memory with 64 bit addresses, and thus is able to exceed the 4Gb limitation of 32-bit addressing (although in practice the limit is smaller anyway due to some addresses being reserved.

This is nothing to do with the precision/range of floating point values (or even the range of integer values).

Way, way, back in the days of the 8086/8088 processors one could add a further chip numbered 8087 to a system (assuming it had the Ďcoprocessorí socket), which would accelerate the floating point calculations. This chip had a stack of very large registers (80 bit actually). There were companion chips 80187, 80287, 80387 and indeed 80487 although the latter was a 486/487 combo and disabled the original 486; and there were also replacement Ď7ís from other manufacturers, plus some that werenít the same architecture like those from Weitek.

In a very simple nutshell, a floating point value would be promoted from REAL*8 to REAL*10 as it entered the coprocessor, various activities would take place, and it would be demoted from *10 to *8 when the results were posted back to memory, thus at a stroke largely eliminating roundoff. Of course, floating point numbers could be kept in REAL*10 (80 bit) in RAM because it is just bytes. Hence, the 64-bit and 80-bit references in the KB.

Since those heady days of the 8087 things have moved on, the 8087 registers have been used for other purposes, and the origins of all this have been forgotten.

As it stands, FTN95 uses 32 bit addressing, but 32, 64 and sometimes 80 bit floating point, with 8, 16, 32 and sometimes 64 bit integers. 64 bit FTN95 will use 64 bit addressing.

Agree about the KB though, although it is the only source for info on some topics ( http://forums.silverfrost.com/viewtopic.php?t=1329 )

Eddie
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John-Silver



Joined: 30 Jul 2013
Posts: 631

PostPosted: Tue Sep 08, 2015 8:02 pm    Post subject: Reply with quote

That's interesting to know ... and I'm sure you've mentioned it somewhere before in a post ..... so like a fool I search for '%bb' (without quotes) to find it ... and ... nothing .... so thinking it might be taking the % as a wildcard I try with bb - nothing, bt - nothing, hen arbitrarly (well not arbitrarily because I saw first that oža post exists with it in title, %lv-zilch, just 'lv' - nada ....... which proves once again my point about the search facility being rather less than profoundly 'deep' in its capabilities.

... and , that location for the %bb needs to be .... documented somewhere Wink

Thanks for the explanation about 64-80 bit adressing/floating-pointing etc....
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JohnCampbell



Joined: 16 Feb 2006
Posts: 1835
Location: Sydney

PostPosted: Thu Sep 10, 2015 5:34 am    Post subject: Reply with quote

For a long time I resented loosing real*10 precision. Moving from x87 to MMX(?) then SSE instructions reduced the precision of the calculations, making the new program versions appear a lesser quality. It certainly created problems for validating updates from old run results.

When did x87 hardware stop being supported ?
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LitusSaxonicum



Joined: 23 Aug 2005
Posts: 1683
Location: Yateley, Hants, UK

PostPosted: Thu Sep 10, 2015 10:25 pm    Post subject: Reply with quote

JC: I lost interest in ASM a long while ago, and since then have forgotten a lot about it, and so it would take a current specialist to tell us if FTN95 uses x87 codes. My post wasn't to claim expertise, just to explain how 64 bit means either precision/range OR addressing. Perhaps Paul will enlighten us with what FTN95 really does.

JS:FTN95.CHM and CWPLUS.ENH have latterly been updated to be far better on %bb that when the KB was the only real resource. See it in the 'format code reference'. Sometimes, you only get to understand the limitations when you try something. I've made toolbars with bb, ib (all variants), tb and tt, and they all have limitations, but I get best results with %tb. %bb is great for a thin horizontal toolbar with only a half-dozen or so buttons, and is one of the things actually improved visually in Win 10.

Eddie
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