Re: Concertina IV Has Arrived

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Sujet : Re: Concertina IV Has Arrived
De : robfi680 (at) *nospam* gmail.com (Robert Finch)
Groupes : comp.arch
Date : 23. May 2026, 19:15:46
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <10usqsi$2g1aa$1@dont-email.me>
References : 1 2 3 4 5 6 7 8 9 10 11 12
User-Agent : Mozilla Thunderbird
On 2026-05-23 5:28 a.m., Anton Ertl wrote:
quadi <quadibloc@ca.invalid> writes:
On Fri, 22 May 2026 15:48:18 +0000, quadi wrote:
>
However, if I have enough opcode space to add a U bit to all the
conditional branch instructions, then I also have enough opcode space to
fix that instead, so I likely will rework this part of the ISA into
something more conventional.
>
I have made the first set of changes, using five-bit condition code fields
to nicely and fully handle both the signed and unsigned cases; I checked
what the Motorola 68000 did, and found that it only provided a complete
set of tests for signed values, but only two tests for unsigned ones.
 I see four tests for unsigned conditions on the 68000
<https://en.wikibooks.org/wiki/68000_Assembly/Conditional_Tests>:
 HI >
LS <=
CC >=
CS <
 
CS may also be called LO
CC may also be called HS

For the signed ones there is
 GT >
LE <=
GE >=
LT <
 
my assumed behavior that
everything should just fail if there's an overflow... is reasonable for
floating-point numbers.
 The usual setup is that FP operations silently overflow to +INF and
underflow to -INF.  They do set sticky flags (called "exceptions" in
Methinks overflow could be to +/- INF and underflow to zero or a denormal.

the IEEE FP standard) on various conditions, including on overflows,
but also on rounding errors ("inexact").
 - anton
If one has CVNZ it is enough for both signed and unsigned integer conditional testing using only four bits.
The CVNZ could be repurposed for float comparisons. V = INF. C=inexact for instance.

Date Sujet#  Auteur
19 May 26 * Concertina IV Has Arrived336quadi
20 May 26 `* Re: Concertina IV Has Arrived335quadi
20 May 26  +- Re: Concertina IV Has Arrived1quadi
20 May 26  `* Re: Concertina IV Has Arrived333MitchAlsup
20 May 26   +* Re: Concertina IV Has Arrived177quadi
20 May 26   i+- Re: Concertina IV Has Arrived1quadi
20 May 26   i+* Byte order and BCD (was: Concertina IV Has Arrived)23Anton Ertl
20 May 26   ii+* Re: Byte order and BCD (was: Concertina IV Has Arrived)6Thomas Koenig
20 May 26   iii`* Re: Byte order and BCD (was: Concertina IV Has Arrived)5Anton Ertl
20 May 26   iii `* Re: Byte order and BCD (was: Concertina IV Has Arrived)4Thomas Koenig
20 May 26   iii  `* Re: Byte order and BCD (was: Concertina IV Has Arrived)3Anton Ertl
20 May 26   iii   `* Re: Byte order and BCD (was: Concertina IV Has Arrived)2Thomas Koenig
20 May 26   iii    `- Re: Byte order and BCD (was: Concertina IV Has Arrived)1Anton Ertl
20 May 26   ii+* Re: Byte order and BCD (was: Concertina IV Has Arrived)7quadi
20 May 26   iii`* Re: Byte order and BCD (was: Concertina IV Has Arrived)6Anton Ertl
20 May 26   iii +* Re: Byte order and BCD (was: Concertina IV Has Arrived)2quadi
21 May 26   iii i`- Re: Byte order and BCD (was: Concertina IV Has Arrived)1Anton Ertl
20 May 26   iii `* Re: Byte order and BCD3Terje Mathisen
21 May 26   iii  `* Re: Byte order and BCD2Anton Ertl
21 May 26   iii   `- Re: Byte order and BCD1Anton Ertl
20 May 26   ii+* Re: Byte order and BCD (was: Concertina IV Has Arrived)7John Levine
20 May 26   iii+- Re: Byte order and BCD1Terje Mathisen
20 May 26   iii`* Re: Byte order and BCD (was: Concertina IV Has Arrived)5quadi
21 May 26   iii `* Re: Byte order and BCD (was: Concertina IV Has Arrived)4John Levine
21 May 26   iii  `* Re: Byte order and BCD (was: Concertina IV Has Arrived)3quadi
21 May 26   iii   +- Re: Byte order and BCD (was: Concertina IV Has Arrived)1Anton Ertl
21 May 26   iii   `- Re: ancient virtual memory, Byte order and BCD (was: Concertina IV Has Arrived)1John Levine
3 Jun 26   ii`* Re: Byte order and BCD (was: Concertina IV Has Arrived)2quadi
3 Jun 26   ii `- Re: Byte order and BCD (was: Concertina IV Has Arrived)1Anton Ertl
20 May 26   i+* Re: Concertina IV Has Arrived151Bernd Linsel
20 May 26   ii`* Re: BCD, was Concertina IV Has Arrived150John Levine
1 Jun 26   ii +* Re: BCD, was Concertina IV Has Arrived15quadi
1 Jun 26   ii i+* Re: BCD, was Concertina IV Has Arrived13John Levine
1 Jun 26   ii ii+* 2s-complement and byte order (was: BCD)9Anton Ertl
1 Jun 26   ii iii+* Re: 2s-complement and byte order (was: BCD)6Thomas Koenig
1 Jun 26   ii iiii`* Re: 2s-complement and byte order (was: BCD)5Anton Ertl
1 Jun 26   ii iiii `* Re: 2s-complement and byte order (was: BCD)4John Levine
2 Jun 26   ii iiii  `* Re: 2s-complement and byte order (was: BCD)3MitchAlsup
2 Jun 26   ii iiii   `* Re: 2s-complement and byte order (was: BCD)2John Levine
2 Jun 26   ii iiii    `- Re: 2s-complement and byte order (was: BCD)1MitchAlsup
1 Jun 26   ii iii+- Re: 2s-complement and byte order (was: BCD)1quadi
1 Jun 26   ii iii`- Re: 2s-complement and byte order (was: BCD)1John Levine
1 Jun 26   ii ii`* Re: BCD, was Concertina IV Has Arrived3quadi
1 Jun 26   ii ii `* Re: BCD, was Concertina IV Has Arrived2John Levine
1 Jun 26   ii ii  `- Re: BCD, was Concertina IV Has Arrived1quadi
1 Jun 26   ii i`- byte order (was: BCD)1Anton Ertl
2 Jun 26   ii `* Re: BCD, was Concertina IV Has Arrived134John Dallman
2 Jun 26   ii  +* Re: BCD, was Concertina IV Has Arrived6quadi
2 Jun 26   ii  i`* Re: BCD, was Concertina IV Has Arrived5MitchAlsup
2 Jun 26   ii  i +* Re: BCD, was Concertina IV Has Arrived2Thomas Koenig
2 Jun 26   ii  i i`- Re: BCD, was Concertina IV Has Arrived1quadi
2 Jun 26   ii  i `* Re: BCD, was Concertina IV Has Arrived2Stephen Fuld
2 Jun 26   ii  i  `- Re: BCD, was Concertina IV Has Arrived1MitchAlsup
2 Jun 26   ii  +- Re: BCD, was Concertina IV Has Arrived1MitchAlsup
2 Jun 26   ii  +* bit order and byte order (was: BCD)5Anton Ertl
3 Jun 26   ii  i+* Re: bit order and byte order (was: BCD)2quadi
3 Jun 26   ii  ii`- Re: bit order and byte order (was: BCD)1Anton Ertl
4 Jun 26   ii  i`* Re: bit order and byte order (was: BCD)2George Neuner
4 Jun 26   ii  i `- Re: bit order and byte order (was: BCD)1Anton Ertl
2 Jun 26   ii  `* Re: endian history, was BCD, was Concertina121John Levine
3 Jun 26   ii   `* Re: endian history, was BCD, was Concertina120quadi
3 Jun 26   ii    +* Re: endian history, was BCD, was Concertina2MitchAlsup
3 Jun 26   ii    i`- Re: endian history, was BCD, was Concertina1quadi
3 Jun 26   ii    `* Re: endian history, was BCD, was Concertina117Thomas Koenig
3 Jun 26   ii     `* Re: endian history, was BCD, was Concertina116quadi
3 Jun 26   ii      +* Re: endian history, was BCD, was Concertina2John Levine
4 Jun 26   ii      i`- Re: endian history, was BCD, was Concertina1Brian G. Lucas
3 Jun 26   ii      +* Re: endian history, was BCD, was Concertina21Thomas Koenig
5 Sep 26   ii      i`* Re: endian history, was BCD, was Concertina20John Dallman
6 Sep 26   ii      i `* Re: endian history, was BCD, was Concertina19Thomas Koenig
6 Sep 26   ii      i  +* Re: endian history, was BCD, was Concertina14David Brown
6 Sep 26   ii      i  i`* Re: endian history, was BCD, was Concertina13Thomas Koenig
6 Sep 26   ii      i  i `* Re: endian history, was BCD, was Concertina12David Brown
6 Sep 26   ii      i  i  `* Re: endian history, was BCD, was Concertina11Thomas Koenig
6 Sep 26   ii      i  i   +* Re: endian history, was BCD, was Concertina9David Brown
7 Sep 26   ii      i  i   i`* Re: endian history, was BCD, was Concertina8MitchAlsup
7 Sep 26   ii      i  i   i +* Re: endian history, was BCD, was Concertina5David Brown
7 Sep 26   ii      i  i   i i`* Re: endian history, was BCD, was Concertina4MitchAlsup
7 Sep 26   ii      i  i   i i `* Re: endian history, was BCD, was Concertina3David Brown
7 Sep 26   ii      i  i   i i  `* Re: endian history, was BCD, was Concertina2MitchAlsup
8 Sep 26   ii      i  i   i i   `- Re: endian history, was BCD, was Concertina1David Brown
8 Sep 26   ii      i  i   i +- Re: endian history, was BCD, was Concertina1David Brown
8 Sep 26   ii      i  i   i `- Re: endian history, was BCD, was Concertina1Thomas Koenig
7 Sep 26   ii      i  i   `- Re: endian history, was BCD, was Concertina1Lawrence D’Oliveiro
6 Sep 26   ii      i  +- Re: endian history, was BCD, was Concertina1John Dallman
7 Sep 26   ii      i  `* Re: endian history, was BCD, was Concertina3John Levine
7 Sep 26   ii      i   `* Re: endian history, was BCD, was Concertina2Thomas Koenig
8 Sep 26   ii      i    `- Re: endian history, was BCD, was Concertina1John Levine
5 Sep 26   ii      `* Re: endian history92Lawrence D’Oliveiro
5 Sep 26   ii       `* Re: endian history91John Savard
5 Sep 26   ii        +* Re: endian history56Terje Mathisen
5 Sep 26   ii        i`* Re: endian history55Thomas Koenig
5 Sep 26   ii        i +* Re: endian history47Terje Mathisen
5 Sep 26   ii        i i`* Re: endian history46MitchAlsup
6 Sep 26   ii        i i +* Re: endian history36John Savard
6 Sep 26   ii        i i i`* Re: endian history35Lawrence D’Oliveiro
6 Sep 26   ii        i i i +* Re: endian history33John Savard
6 Sep 26   ii        i i i i+* Re: endian history10Lawrence D’Oliveiro
8 Sep 26   ii        i i i ii`* Re: endian history9John Savard
8 Sep 26   ii        i i i ii `* Re: endian history8Lawrence D’Oliveiro
8 Sep 26   ii        i i i ii  `* Re: endian history7John Savard
7 Sep 26   ii        i i i i`* Re: endian history22MitchAlsup
7 Sep 26   ii        i i i `- Re: endian history1Tim Rentsch
6 Sep 26   ii        i i +* Re: endian history5BGB
7 Sep 26   ii        i i `* Re: endian history4Terje Mathisen
5 Sep 26   ii        i `* Re: endian history7Lawrence D’Oliveiro
6 Sep 26   ii        `* Re: endian history34Lawrence D’Oliveiro
20 May 26   i`- Re: Concertina IV Has Arrived1MitchAlsup
20 May 26   +* Re: Concertina IV Has Arrived123quadi
21 May 26   +* Re: Concertina IV Has Arrived6quadi
25 May 26   `* Re: Concertina IV Has Arrived26quadi

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