More undocumented instructions

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3 total messages Started by Peter Clare Tue, 20 Mar 1990 14:50

#504

Author: Peter Clare
Date: Tue, 20 Mar 1990 14:50

54 lines
2141 bytes

Further to the recent discussion on undocumented transputer instructions,
here are some more instructions that I am aware of (in addition to the
"testhardchan" instruction mentioned previously).  I know little more
about these instructions other than their operation codes and their
mnemonics:

    Operation code (hex)		Mnemonic
    --------------------		--------
		23			testlds
		24			testlde
		25			testldd
		26			teststs
		27			testste
		28			teststd
		2D			testhardchan
		80			fpsttest
		85			fpldtest
		A7			fpentry3
		A9			fpentry2

>From the mnemonics, one can guess at what some of these instructions might
do.  In particular, the two extra fpentry instructions look interesting.
If they work like the normal fpentry instruction then they could lead to
a whole load of extra floating point instructions.  If you are familiar
with the transputer instruction set then you will see that these extra
instructions fill in some of the "gaps" between the documented instructions.

Here are some questions.  Can anyone on the transputer grapevine provide
any answers?

    1)	Are there any more undocumented instructions?

    2)	What do these instructions do?  How do they affect registers and
	what are the cycle times?

    3)	Are any of these instructions of any real use other than for testing
	purposes?

    4)	Which instructions are supported on which types of transputer?


===============================================================================
Peter Clare
THORN EMI Central Research Laboratories
Dawley Road
Hayes
Middlesex
UB3 1HH

Tel:		01-848-6521
Fax:		01-848-6565
Eurokom:	Peter Clare THORN EMI
email:		clare@thorn-emi-crl.co.uk
===============================================================================

Re: More undocumented instructions

#506

Author: Steven Ericsson Zenith
Date: Tue, 20 Mar 1990 23:12

32 lines
1708 bytes

In article <9003201450.AA01756@flay.thorn-emi-crl.co.uk>,
clare@tesun2.UUCP (Peter Clare) writes:
   I know little more
  about these instructions other than their operation codes and their
  mnemonics:

     Operation code (hex)		Mnemonic
     --------------------		--------
 		23			testlds
 		24			testlde
 		25			testldd
 		26			teststs
 		27			testste
 		28			teststd

...
 
     2)	What do these instructions do?  How do they affect registers and
	what are the cycle times? 

You mean the load and store Status Register, E Register and D Register?
Nah ... you don't want to know :-) (tease!). Maybe you should ask an
INMOS FAE... maybe he doesn't know. Maybe you should read my book when
it comes out (how to put the fear of god in INMOS :-) Nah! just kidding
guys ... honest!)

--
.                                                                        .
Steven Ericsson Zenith              *            email: zenith@cs.yale.edu
Department of Computer Science      |            voice: (203) 432 1278
Yale University 51 Prospect Street New Haven CT 06520 USA.
     "All can know beauty as beauty only because there is ugliness"

Re: More undocumented instructions

#527

Author: Malcolm Boffey
Date: Mon, 26 Mar 1990 17:38

21 lines
1728 bytes

This is in response to queries about undocumented instructions for loading and
storing the D, E, S registers.

In addition to the published registers :- A, B, C, I, W, queue pointers etc,
there are a few (D, E) that are used to hold intermediate values in some of
the instructions. As they are not saved during interrupts, there seems little
use for them in low priority, and they can only be used safely at high priority
if you know what instructions are able to corrupt them (which I don't). Anyway,
it is easier to use another local variable.
	The status register (S) holds miscellaneous bits of state like the Error
flag and the HaltOnError flag, for which there are already enough instructions
to access and alter them.
	There are one or two other instructions that are used for testing, none
of them terribly usefull or interesting. Also, it is more or less a certainty
that they will be discontinued in future transputers, or at least change their
function significantly.
	malc.
 Malcolm Boffey, Transputer Group, Inmos.   | Inmos Ltd,
UK:   malc@inmos.co.uk                      | 1000 Aztec West, Almondsbury,
US:   malc@inmos.com                        | Brisol BS12 4SQ. 
UUCP: ...uunet!mcsun!ukc!inmos!malc         | Tel. +44 454 616616 x522

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