19 Feb
2009
19 Feb
'09
9:27 p.m.
There was also the NEC V20, which was pin for pin compatible with the
8088. It was a CMOS part. There were a few instructions that the V20
executed in fewer clock cycles than the 8088 (multiply comes to mind),
causing some motherboard vendors to install a V20, and the sell a 10mhz
motherboard as a 12mhz motherboard.
The truly great feature of the V20 was the 8080 emulation mode. When a
special opcode was executed, the processor switched to 8080 mode, a very
fast 8080. I made several CP/M (80) systems using a V20 processor, with
a small prom to put the v20 into 8080 mode. I could then switch back
into 16 bit mode to implement a ram disk.
Les
20 Feb
20 Feb
12:17 p.m.
On 19 Feb 2009 at 19:27, Les Hildenbrandt wrote:
There was also the NEC V20, which was pin for pin
compatible with the
8088. It was a CMOS part. There were a few instructions that the V20
executed in fewer clock cycles than the 8088 (multiply comes to mind),
causing some motherboard vendors to install a V20, and the sell a 10mhz
motherboard as a 12mhz motherboard.
The problem with the V20's 8080 emulation was that it was buggy (I
have a few MicroNotes on the subject and can even claim to have
discovered one of the bugs). For me, the V20 ultimately proved to be
more useful by providing many of the 80186/286 instructions that the
8080 lacked. Use of a V20 with an 8087 NDP could also create
problems of its own, so the added functionality was not without its
own problems.
It's also worthwhile to mention that the V20/30 has instructions that
none of the Intel x86 members has, such as packed BCD string
arithmetic.
I believe that the emulation mode features extended to the V40 and
V50 chips also. At least that's what my databook claims.
Cheers,
Chuck
7:59 p.m.
Chuck Guzis wrote:
It's also worthwhile to mention that the V20/30
has instructions that
none of the Intel x86 members has, such as packed BCD string
arithmetic.
I have never found a decent resource on NEC V20 special opcode
programming; the only stuff I've found has been on how to detect an NEC
through bugs, and searching via google has been unproductive for the
last 20 minutes. Is there a resource for what the extended instructions
were, or is that lost to paper history?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
8:29 p.m.
On 20 Feb 2009 at 18:59, Jim Leonard wrote:
I have never found a decent resource on NEC V20
special opcode
programming; the only stuff I've found has been on how to detect an NEC
through bugs, and searching via google has been unproductive for the
last 20 minutes. Is there a resource for what the extended instructions
were, or is that lost to paper history?
Dunno--my reference is "uPD70108/70116 Low-Power CMOS Microprocessors
User/s Manual" August 1985, Stock No. 500350. Sort of a strange read
if you're used to Intel terminology, as NEC uses their own. For
example, the register names are different (AW,BW,CW,DW,IX,IY; PS,
DS0, DS1, SS) and mnemoics are different--e.g., Intel AAM is called
CVTBD (convert bindary to decimal). Just enough difference to make
you think that NEC rewrote the Intel manual in Frisian.
There's also a V-Series general reference namual that describes all
of the members of the V-family, but not in any great detail.
Cheers,
Chuck
8:54 p.m.
Chuck,
Personally I loved the Nec V25 and V35 microcontrollers for small
projects. For a "decent resource" on the Nec V20/30 did you look at
the Nec User's Manual for the V Series (~ 1 thick, Circa 1992)?
I have one around here somewhere.
Jim
At 07:59 PM 2/20/2009, you wrote:
Chuck Guzis wrote:
[]
Jim
e-mail: JeLynch at stny.rr.com
website: <http://www.gluons.us>www.gluons.us
It's also worthwhile to mention that the
V20/30 has instructions
that none of the Intel x86 members has, such as packed BCD string arithmetic.
I have never found a decent resource on NEC V20 special opcode
programming; the only stuff I've found has been on how to detect an
NEC through bugs, and searching via google has been unproductive for
the last 20 minutes. Is there a resource for what the extended
instructions were, or is that lost to paper history?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
9:14 p.m.
On 20 Feb 2009 at 20:54, Jim Lynch wrote:
Chuck,
Personally I loved the Nec V25 and V35 microcontrollers for small
projects. For a "decent resource" on the Nec V20/30 did you look at
the Nec User's Manual for the V Series (~ 1 thick, Circa 1992)?
Yup, I've got it, but the V20/30-specific one is better (IMOHO) on
the nitty-gritty for programmers of those chips.
I liked the V40/V50 a lot--80186-ish, but with signals to tell you
which segment register was being used for memory references, so you
could have up to 4 separate 1MB memory spaces.
Cheers,
Chuck
9:24 p.m.
On Fri, 20 Feb 2009, Chuck Guzis wrote:
Date: Fri, 20 Feb 2009 18:14:49 -0800
From: Chuck Guzis <cclist at sydex.com>
Reply-To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Subject: Re: 8088 vs. 80c88
On 20 Feb 2009 at 20:54, Jim Lynch wrote:
We used V40s a lot in the 90's. Their DMA controller was really nice as well,
with 1M direct addressing. We drove 320x240 mono LCDs with minimal hardware,
DMAing the data nibble and the framing signals directly to the LCD. 1 bit in
memory was used as a long PDM stream for contrast adjust.
Peter Wallace
Chuck,
Personally I loved the Nec V25 and V35 microcontrollers for small
projects. For a "decent resource" on the Nec V20/30 did you look at
the Nec User's Manual for the V Series (~ 1 thick, Circa 1992)?
Yup, I've got it, but the V20/30-specific one is better (IMOHO) on
the nitty-gritty for programmers of those chips.
I liked the V40/V50 a lot--80186-ish, but with signals to tell you
which segment register was being used for memory references, so you
could have up to 4 separate 1MB memory spaces.
Cheers,
Chuck
21 Feb
21 Feb
4:20 a.m.
On Fri, 20 Feb 2009, Chuck Guzis wrote:
I liked the V40/V50 a lot--80186-ish, but with signals
to tell you
which segment register was being used for memory references, so you
could have up to 4 separate 1MB memory spaces.
But that is not a NEC specific feature, these signals can be found on the
i8086 and i8088, too.
Christian
12:12 p.m.
On 21 Feb 2009 at 10:20, Christian Corti wrote:
But that is not a NEC specific feature, these signals
can be found on the
i8086 and i8088, too.
Going back to the 8086 datasheet, I see that you're right--the S3/S4
status bits multiplexed onto the address lines. I've never seen an
application that uses them that way on the 8086.
Thanks,
Chuck
9:10 a.m.
2009/2/20 Chuck Guzis <cclist at sydex.com>:
The problem with the V20's 8080 emulation was that
it was buggy (I
have a few MicroNotes on the subject and can even claim to have
discovered one of the bugs).
Could you please add some notes to the Wikipedia article about NEC V20/Vxx :
http://en.wikipedia.org/wiki/NEC_V20
To All: does anyone have "V2080 CPeMulator" programm mentioned on this page ?
--
-=AV=-
1:09 p.m.
On 21 Feb 2009 at 17:10, Alexander Voropay wrote:
2009/2/20 Chuck Guzis <cclist at sydex.com>:
I'll make a note to dig out my MicroNotes this upcoming week and put
something together.
The problem with the V20's 8080 emulation was
that it was buggy (I
have a few MicroNotes on the subject and can even claim to have
discovered one of the bugs).
Could you please add some notes to the Wikipedia article about NEC V20/Vxx :
http://en.wikipedia.org/wiki/NEC_V20 To All: does anyone have "V2080 CPeMulator"
programm mentioned on this page ?
I don't think so, but I know I do have a "CPMulator" from GFI
Electronics of Olathe, KS. (One of many such programs).
Cheers,
Chuck
--
-=AV=-
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alec＠sensi.org -
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