vereijken@rulcri.leidenuniv.nl (Jan Joris Vereijken) (03/26/91)
Hi,
I have run into something very strange: under Turbo Pascal one can choose to
generate specific 80286 code ($G+ switch). This code is not supposed to run on
XT-like (8088/8086-based) machines. However, it seems to do...
Facts:
- My system is V30-based clone, using a BIOS called "PC-SPEED V1.50"
(Actually it's a modified Atari ST, it runs about every MSDOS thing
just fine. I am sure I have a V30, as I installed it myself.)
- I compiled (for 80286) BGIDEMO.PAS, TCALC.PAS and a few (big) things
I wrote myself.
- The code generated DID differ from the "normal" code (for 8088). I checked
this. The 80286-code is shorter, and is generated faster(!).
- All the above programs ran like a charm on my V30 machine!
- I did NOT benchmark the speed of the 8088 vs. 80286 code. (Actually I
did, but then proclaimed my results unreliable).
This is not supposed to happen! I want my machine to be locked up! I PAID for
that (Borland manuals say it should lock up).
I have given it some thought and have come up with the following:
- Maybe a V30 (which is a enhanced 8086) can handle the 80286 instructions
Turbo 6.0 generates? (Of course not ALL 80286 instruction, but maybe TP6.0
only generates a proper subset.)
- Maybe I have a BIOS that catches the 80286 instructions and emulates them?
(Is this possible somehow? I only have a limited 8086-machinecode
experience.)
- Maybe the programs I ran did in fact NOT function properly, but I did not
notice? (Say again? Me not notice???)
- Maybe I'm going crazy? (I'm not crazy! I'm a dictionary!)
However, I still do not figure why things are as they are (a well-known concept
when applied to life-at-large).
Who sheds some light on the matter?
Thanx!
- Jan Joris -
forchk@rullf2.LeidenUniv.NL
vereijken@hlerul5.bitnet
(P.S.: Reply to me personally too, as I do not subscribe to this list.)
mnrausch@immd4.informatik.uni-erlangen.de (Martin Rausche) (03/26/91)
vereijken@rulcri.leidenuniv.nl (Jan Joris Vereijken) writes: >Hi, > >I have run into something very strange: under Turbo Pascal one can choose to >generate specific 80286 code ($G+ switch). This code is not supposed to run on >XT-like (8088/8086-based) machines. However, it seems to do... > >Facts: > > - My system is V30-based clone, using a BIOS called "PC-SPEED V1.50" >[some stuff deleted] > - All the above programs ran like a charm on my V30 machine! > >[some stuff deleted] > >Thanx! > >- Jan Joris - > >forchk@rullf2.LeidenUniv.NL >vereijken@hlerul5.bitnet > >(P.S.: Reply to me personally too, as I do not subscribe to this list.) > TP6.0 generates code for the 80286, but it uses only the real mode extensions of the 80286. The NEC-V30 chip can deal with this instructions. There is no mystery. Have fun. Martin. --- ------------------------------------------------------------------------------ | Martin Rausche | | EMail: mnrausch@immd4.informatik.uni-erlangen.de | | Trust me, I know what I'm doing -- Sledge Hammer | ------------------------------------------------------------------------------
dmurdoch@watstat.waterloo.edu (Duncan Murdoch) (03/26/91)
In article <1991Mar26.010615.1@rulcri.leidenuniv.nl> vereijken@rulcri.leidenuniv.nl (Jan Joris Vereijken) writes: >Hi, > >I have run into something very strange: under Turbo Pascal one can choose to >generate specific 80286 code ($G+ switch). This code is not supposed to run on >XT-like (8088/8086-based) machines. However, it seems to do... > >Facts: > > - My system is V30-based clone, using a BIOS called "PC-SPEED V1.50" > (Actually it's a modified Atari ST, it runs about every MSDOS thing > just fine. I am sure I have a V30, as I installed it myself.) > - I compiled (for 80286) BGIDEMO.PAS, TCALC.PAS and a few (big) things There's been some discussion of this on Fidonet. It seems that the $G+ command only generates instructions that are on the 80186; V20 and V30 chips also support these instructions. There's a list of exactly which instructions the $G+ command allows in the manual; if you have a V30 manual, you can verify that it supports all of them. Duncan Murdoch dmurdoch@watstat.waterloo.edu
jamesp@world.std.com (james M peterson) (03/27/91)
The V-30 chip does in fact have a subset of the 286 instruction set. I've been using this "feature" occasionally. Its mostly the enhanced move and such codes. jamesp@world.std.com
ebergman@isis.cs.du.edu (Eric Bergman-Terrell) (04/02/91)
I used to use a Zenith which used (I believe) an NEC V-20 which was a 80186 clone. Turbo C generated 80186 instructions which the Zenith happily executed. Result: prog. ran ~10% faster & code was slightly smaller... Maybe the same thing is happening to you? Terrell