Shareware Grab Bag/Shareware Grab Bag.iso/007/necv20pc.arc/NECV20PC.PRT

Text File | 1986-03-17 | 30KB | 765 lines

Current Meeting : bsilverio/mtgs/ibmpc (ibmpc)
Chairman        : bsilverio
Current xcn     : [0400]
New transactions: NONE

Forum: p 632
[0632] ( 39 lines) bsilverio    02/22/86 17:12 ibmpc
Subject:RE:NEC V20 Clock Cycle Times
*(        from Multics ibmpc meeting on 02/22/86 )*

Date: 15 Oct 1985 09:33:08 PDT
From: Jeff La Coss <[e-mail]>
To: [e-mail]
cc: [e-mail]


 somebody wanted reassurance from a hardware type that a v-20 would
run in a pc? simple - burn a couple extra bucks/throw away a bit of
potential speed/get the 8mhz version. works great.

 generally speaking, the reason clocks are spec'ed at 50% duty cycle
is because they are counting on both the rising and falling edges of
the clock to shuffle data along some series of dynamic devices. thus
if the clock looks like

    _             _
___| |___________| |_______

rather than

    ______        ______
___|      |______|      |_______

 data set into, say, the master stage of a flip-flop might not
(probably won't) have time to propagate through the present stage to
be stable at the input of the slave stage, which is clocked by the
falling edge.  faster devices allow you to cheat on clock symmetry as
long as the shortest part of the actual clock cycle meets the
shortest-duration spec for the device.

jeff

p.s. I've heard a bunch of conflicting noise re: how NEC made the
v-20. If the ripped-off microcode/pla story is false, NEC sure stuck
it to Intel....

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Forum: p 619:621
[0619] ( 16 lines) bsilverio    02/22/86 17:11 ibmpc
Subject:NEC V20 and Duty Cycle Query
*(        from Multics ibmpc meeting on 02/22/86 )*

Date:  Sat, 12 Oct 85 12:03 EDT
From:  [e-mail]
To:  [e-mail]

Can someone interpret the NEC V20 duty cycle message for a non-hardware
person?  To me, a duty cycle exceeded on a piece of mechanical equipment
means it dies from overwork.  Does this message mean that one's clock
chip will catch fire?  Or does it just mean that if you plug in a V20
that it might stop performing correctly for no apparent reason and need
to be rebooted?

Brian

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[0620] ( 20 lines) bsilverio    02/22/86 17:11 ibmpc
Subject:NEC V20 Clock Cycle Times
*(        from Multics ibmpc meeting on 02/22/86 )*

Date: 12 Oct 1985 02:52-PDT
From:  William "Chops" Westfield <[e-mail]>
To: [e-mail]


Someone warned that the NEC v20 clock was 50% duty cycle, and that
the minimum clock high time of 85 nS was violated by the IBMPC,
which provided about 71 nS.  Well, My NEC v20 data sheet (dated
March, 1985) says that the minimum clock high time is 69 nS,
and not 85 nS, which is closer than it ought to be to the 71 nS
in the IBM PC, but is pretty likely to work.

The minimum clock high time on the 8Mhz part is 50nS, so things
may be tighter in an 8MHz system.

BillW

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[0621] ( 23 lines) bsilverio    02/22/86 17:11 ibmpc
Subject:RE:NEC V20 Clock Cycle Times
*(        from Multics ibmpc meeting on 02/22/86 )*

Date:     Mon, 14 Oct 85 12:26:00 PDT
From:     [e-mail]
To:       [e-mail]


Within the last two weeks, I called NEC Mountain View, 415-960-6000, and
received a copy of the May 1985 "Preliminary Information" on the V20 and
v30, both 5 and 8 MHz versions.  This is a nicely bound manual, complete
with a table of all the opcodes, though NEC uses different mnemonics than
Intel to avoid charges of copyright infringement.  Page 7 of this document
calls for the minimum clock high time to be 69 ns and low time to be 90 ns
for the 5 Mhz chip, a 43% (?) duty cycle.  The former number is within,
though perhaps uncomfortably close to, the 71 ns for the Intel 8284 clock
chip. The 8 MHz version values are 50 and 60 ns respectively, a 45% duty
cycle.  The V30 spec quotes the same numbers.

                                                Stephen Walton
                                                Caltech Solar Astronomy
                                                walton%deimos@cit-hamlet

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Forum: p 590
[0590] ( 38 lines) bsilverio    02/22/86 17:09 ibmpc
Subject:NEC V20 Warning
*(        from Multics ibmpc meeting on 02/22/86 )*

From: "Raymond D. Dunn" <[e-mail]>
Date: 9 Oct 85 19:02:54 GMT


Although many, including myself, are successfully using an NEC V20 as a
direct replacement for the Intel 8088 in our PC's, it looks as if this may
not be a good idea in all but a hacking environment.

I am indebted to my colleague Humphrey Brown, for the following information:-

"The following caution should be issued in connection with the widely touted
NEC V20 microprocessor (P/N 70108) as a plug-in upgrade replacement for the
8088 in personal computers.

The specification for the V20 calls for a clock with a 50% duty cycle.  The
clock driver for the 8088 delivers a clock of 33% duty cycle.  NEC's data
sheet for the V20 specifies a minimum clock high time of 85nS and a low time
of 90nS.  Intel gives a minimum clock high time for the 8284 of
1/3 tclcl+2nS, which for a clock frequency of 4.77Mhz, yields 71nS.

While the chances are that this will work anyway, those who wish to try it
should note that there are no guarantees.

I have'nt got the data sheet for the 8Mhz part yet, but by judicious
extrapolation, that part will require a clock high time of about 48nS, thus
that part of the clock requirement will be met.  However, NEC are quite
explicit in their data sheets as to the need for a 50% duty cycle.

The solution to the mismatch between the Intel clock generator and the NEC
processor might be to also plug in the NEC clock driver (P/N 71011) in place
of the 8284, since it appears to be pin-compatible, but note that the 71011
divides the external frequency by 2, not 3 as for the 8284."

Ray Dunn.   ..philabs!micomvax!othervax!ray

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Forum: p 537
[0537] ( 16 lines) bsilverio    02/17/86 15:09 ibmpc
Subject:V20 Opcodes Prepare & Dispose
*(        from Multics ibmpc meeting on 02/16/86 )*

Date: Tuesday,  1 Oct 1985 12:29:17-PDT
From: [e-mail]  (David Dantowitz -- LTN2-2/H07)


   There have been many notes on the V20 and its extended instruction
set, but could someone present a more explicit description of what
the PREPARE and DISPOSE opcodes do ?

   David Dantowitz
   617-486-6957

[Aren't these extended Intel instructions from the 186 and 286? -wab]

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Forum: p 422
[0422] (184 lines) bsilverio    02/17/86 14:59 ibmpc
Subject:NEC V30: Availability, Benchmarks, Info
*(        from Multics ibmpc meeting on 02/16/86 )*

From: Kim DeVaughn <[e-mail]>
Date: 19 Sep 85 18:03:03 GMT
To:       [e-mail]


By the way, the actual NEC part numbers for the V30
series of chips are:

        uPD70116D-8     8 MHz, ceramic
        uPD70116D-5     5 MHz, ceramic
        uPD70116C-8     8 MHz, plastic
        uPD70116C-5     5 MHz, plastic

(Replace the "16" with "08" and you get the V20 (8088 compatible) p/n's.)

NEC's address (so you can get a spec) is:

        NEC Electronics, Inc.           ph: 800-632-3532 in California
        401 Ellis St.                       800-632-3531 elsewhere
        PO Box 7241
        Mt. View, CA    94039

Note: I am not associated with any of the above companies, except as a
      satisfied customer.

Ok, now for some quick-and-dirty before/after benchmark numbers:

System:    Fujitsu u-16s w/8087 (8 MHz)
SCP:       MS-DOS 2.11
Compiler:  TurboPascal 3.01A (w/8087 support)

Benchmark:      program bench(output);

                var
                  i,j,k,l:      integer;
                  r:            real;
                  s:            string[100];
                  t,u:          string[50];

                begin
                  i := 0;
                  r := 0.0;
                  s := '';
                  t := 'ABCDEFGHIJKLMNOPQRSTUVWXYABCDEFGHIJKLMNOPQRSTUVWXY';
                  u := 'abcdefghijklmnopqrstuvwxyabcdefghijklmnopqrstuvwxy';

                  repeat until keypressed;   {start timing when a key is hit}

                  for j := 1 to 1000 do
                      for k := 1 to 1000 do     {1 to 50 for string test}
                          for l := 1 to 10 do
                              {one of:          }
                               i := i + 1;      {integer}
                              {r := r + 1.0;}   {real}
                              {s := t + u;  }   {string assign/concatinate}

                  writeln(^G,i{or r, or s}); {stop timing when the bell rings}
                end.


Results:             |    8086     |    V30      |  %-improvement
          ---------------------------------------------------------
           integer   |   150.75    |   144.30    |     4.3%
           real      |  1489.24    |  1357.94    |     8.8%
           string    |   497.50    |   296.25    |    40.5%      <---- !!
                     |             |             |
           Mgen +    |  1012.14    |   935.84    |     7.5%
           Msho ++   |    23.09    |    18.35    |    20.5%

           Times are in seconds.
         + Mgen is a Mandelbrot set generating program (compute intensive).
        ++ Msho is a display routine for Mgen's data   (data-move intensive).

The machine sucessfully ran all the diagnostics, floppy and hard-disk tests,
rupt driven communication/modem program, etc.  In short, the s/w couldn't
tell the difference (obviously, there were no s/w timing loops in anything
I ran ... at least none that were critical).

Subjectively, MASM seems to run about 20%-30% faster, and scrolling thru text
in various editors is quite noticeably faster.  I am a little surprised by
the integer vs. real results (I expected to see the least improvement in code
that uses the 8087); I haven't looked at the code Turbo generates tho.  In
any case, a performance improvement of 15%-20% for average, interactive work
is well worth $21.51, I'd say (and the chip was only slightly warm after a
couple of hours of experimentation)!


Here's a look at the "extra" instructions in the V30 and V20 (note that these
are NEC's mnemonics):

80186 compatible:       PUSH imm        . pushes immediate data onto the stack
                        PUSH R          . pushes 8 general registers onto stack
                        POP R           . pops 8 general registers from stack
                        MUL imm         . executes 16-bit multiply of register
                                          or memory contents by immediate data
                        SHL imm8        . shifts/rotates register or memory by
                        SHR imm8          immediate value
                        SHRA imm8
                        ROL imm8
                        ROR imm8
                        ROLC imm8
                        RORC imm8
                        CHKIND          . checks array index against
                                          designated boundaries
                        INM             . moves a string from I/O port to mem
                        OUTM            . moves a string from mem to I/O port
                        PREPARE         . allocates an area for a stack frame
                                          and copies previous frame pointers
                        DISPOSE         . frees the current stack frame on a
                                          procedure exit

NEC unique:             INS             . insert bit-field
                        EXT             . extract bit-field
                        ADD4S           . adds packed decimal strings
                        SUB4S           . subtract one packed decimal string
                                          from another
                        CMP4S           . compares two packed decimal strings
                        ROL4            . rotates one BCD digit left thru AL
                                          lower 4 bits
                        ROR4            . rotates one BCD digit right thru AL
                                          lower 4 bits
                        TEST1           . tests a sspecified bit; sets/resets
                                          zero-flag
                        NOT1            . inverts a specified bit
                        CLR1            . clears a specified bit
                        SET1            . sets a specified bit
                        REPC            . repeats next (string) instruction
                                          until carry-flag is cleared
                        REPNC           . repeats next (string) instruction
                                          until carry-flag is set
                        FP02            . additional float-pt processor call

8080 emulation mode:    BRKEM           . start 8080 emulation mode
                        RETEM           . return from emulation mode
                        CALLN           . call native-mode (V30) subroutine
                                          from within 8080 emulation mode
                                          (use normal RETI to return)


Looks like NEC just may have developed the "Z-80" of the 8086-style
16-bitters ...

Enjoy!

/kim

"The difference between science nd the fuzzy subjects is that science
requires reasoning, while those other subjects mearly require scholarship."
-- Lazarus Long

[generic disclaimer]
--

UUCP:  {decvax,ucbvax,ihnp4}!decwrl!mips!kim
DDD:   415-960-1200
USPS:  MIPS Computer Systems Inc,  1330 Charleston Rd,  Mt View, CA 94043

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Forum: p 399:401
[0399] ( 20 lines) bsilverio    02/14/86 13:28 ibmpc
Subject:NEC V20 and Other 8088-Family Chips in CMOS?
*(        from Multics ibmpc meeting on 02/13/86 )*


From: Gordon Letwin <microsoft!gordonl@uw-beaver>
Date: 16 Sep 85 14:33:59 GMT


I installed a NEC 8088-look-alike in my homebrew system, not because
its 7% faster (as measured) but because its CMOS and drinks less juice.
(130 ma to 30 ma).  The question is, are CMOS equivalents of the other
system chips available?  The 8284, the 8205, the 8155, etc., etc.
If anyone knows of a manufacturer of such CMOS goodies, and maybe
part #'s, please let me know via email.

          thanks
          gordon letwin

          uw-beaver!microsoft!gordonl

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[0400] ( 14 lines) bsilverio    02/14/86 13:28 ibmpc
Subject:NEC V20 and 8087
*(        from Multics ibmpc meeting on 02/13/86 )*

Date: Thu 19 Sep 85 14:34:27-PDT
From: Doug <[e-mail]>
To: [e-mail]

I've got a V20 installed in a Faraday XT clone, with an 8087, and
have not seen any problems so far.  There has been some noticeable
speed-up in large assemblies, and Dbase applications.
          ...!hplabs!faunt    [e-mail]
-------


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[0401] ( 19 lines) bsilverio    02/14/86 13:28 ibmpc
Subject:NEC V20 in a Seequa Chameleon
*(        from Multics ibmpc meeting on 02/13/86 )*

Date: Friday, 20 Sep 1985 10:26:15-PDT
From: [e-mail]  (David Dantowitz -- LTN2-2/H07)

  I recently received my V20 and installed it in my Seequa Chameleon.
The new CPU works well with my 8087 and was easily installed.  The Tech
people at Seequa were not sure that the CPU would function properly, but
thus far it appears to work fine.  I have experienced only one problem
with software and that is that the program "Lode Runner" will not function
on my V20.  This is a game by Broderbund Software, and although it loads
fine and will display the high scores, the program hangs when it tries
to start up a new game.  If anyone with a V20 has run this program
please let me know, as it could also be a Chameleon related problem.

   David Dantowitz
   617-486-6957

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Forum: p 387:388
[0387] ( 76 lines) bsilverio    02/14/86 13:25 ibmpc
Subject:NEC V20 for 8088 and 8087
*(        from Multics ibmpc meeting on 02/13/86 )*

From: Kim DeVaughn <[e-mail]>
Date: 13 Sep 85 22:46:26 GMT
To:       [e-mail]

[ ... ]

> <>When I bought an 8087 to put in my IBM PC, it came with a new 8088.
> I was told to replace the 8088 when I put in the 8087 because the old
> 8088 might not work properly with the 8087.
> <>Question:  Is this kind of matching really necessary, and, if so,
> does one have to worry about replacing an 8088 with a V20 in a system
> with an 8087?  (Also same question for 80286, V30, 80287.)

Ummm, let's see if I remember this correctly ...

It seems that in a very early release of the 8088 (8086, both, ?), there
was a bug that could cause problems when altering a segment register.  The
most common manifestation was in restoration of the SS:SP reg pair from
a previously stored pair of values such as:

                              mov       SS,StakSegSav
                              mov       SP,StakOffSav

The 808x chips are designed such that an interrupt (should one occur) will
not be recognized immediately after the seg-reg altering instruction, but
will be held pending until after the execution of the instruction that
*follows* it has completed.  This is so you don't end up with a meaningless
SS:SP pointer, for example.

Well, these early chips would go ahead and take the rupt immediately, which
led to an occasional crash ... a tough one to isolate, I might add.

I believe that the inclusion of a new 8088 with the 8087 purchase was just
used as an opportunity to try and purge the early chips out of as many
systems as possible.  While it is true that the 8087 can be setup to
generate a rupt on various error conditions (so a user written handler can
try to clean things up), in practice, I believe most packages rely on the
internal 8087 error-handlers (defined as part of the IEEE-754 standard).

In summary, I would not expect a problem with the V20/V30 chips, as the
808x architecture is very well understood now ... of course there may be
other surprises lurking in this new implementation of (and extension to)
that architecture.  Now if I can just get my hands on an 8 MHz V30 ...

BTW ... there *was* a release of PC-DOS that had a related problem.  There
were several places in the code where the programmer coded:

                              mov       SP,fooPlace
                              mov       SS,barPlace
instead of:

                              mov       SS,...
                              mov       SP,...

I don't recall the particular release, and I *think* it was only for the
PC-Jr.  There was a set of patches to correct this problem published in
"PC Tech Journal" magazine sometime within the past year or so.  Anyone
experiencing occasional, unexplainable, un-reproducable crashes might want
to check this out.


/kim

"You can have peace. Or you can have freedom. Don't ever count on having
both at once."  --- Lazarus Long.



--
UUCP:  {decvax,ucbvax,ihnp4}!decwrl!mips!kim
DDD:   415-960-1200
USPS:  MIPS Computer Systems Inc,  1330 Charleston Rd,  Mt View, CA 94043

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[0388] ( 47 lines) bsilverio    02/14/86 13:25 ibmpc
Subject:NEC chips and 1.2MB diskettes
*(        from Multics ibmpc meeting on 02/13/86 )*

From: [e-mail]
Date:     15 Sep 85 10:42 EDT
To: harvard![e-mail]

          To prevent any further requests for telephone numbers,
here is the number from the NEC '84 data book:

          415-960-6000

Ask them for the U.S. (or other) rep near you. Ask nothing else
of these people, they are not likely to help you much.

          Phone your rep. and ask for the distributor(s) near you.
You may also ask these people for literature. Request by the actual
part numbers:

          V20 = uPD70108Dx    where x= 5 MHz or 8MHz
          V30 = uPD70116Dx

There are users manuals as well as data sheets. Also there is
preliminary documentation on the V40/V50. These things contain
everything but the kitchen sink. They are available as prototype
boards only at this time. So as not to waste a phone call, you can
also ask for uPD765 floppy disk controller specs (the IBMPC board).
You never know when it may come in handy...

          Anyway, one of the distributors will be able to sell you
<1000 V20's or V30's. Be forwarned, the V30 is in rework at this
moment and you will encounter significant delays. First price break
is at 25 pieces. The V20 was quoted to me at $22.30 1-24 and $18.20
25-?.

          Of course, there is the "back door" route to the
distributor, look him up in the yellow pages. Good luck.
____________

Gerald Lotto - Harvard Chemistry Dept.

UUCP:  {genrad,cbosgd}!wjh12!h-sc4!harvard!lhasa!lotto
       {seismo,harpo,ihnp4,linus,allegra,ut-sally}!harvard!lhasa!lotto
ARPA:  [e-mail]
CSNET: lotto%harvard@csnet-relay


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UUCP:  {decvax,ucbvax,ihnp4}!decwrl!mips!kim
DDD:   415-960-1200
USPS:  MIPS Computer Systems Inc,  1330 Charleston Rd,  Mt View, CA 94043

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[0363] ( 18 lines) bsilverio    02/14/86 13:21 ibmpc
Subject:NEC V20 When 8087 is Used?
*(        from Multics ibmpc meeting on 02/13/86 )*

From: Henry Schaffer <[e-mail]>
Date: 10 Sep 85 20:21:03 GMT


When I bought an 8087 to put in my IBM PC, it came with a new 8088.
I was told to replace the 8088 when I put in the 8087 because the old
8088 might not work properly with the 8087.  I didn't feel like
experimenting, so I did the replacement.

<>Question:  Is this kind of matching really necessary, and, if so,
does one have to worry about replacing an 8088 with a V20 in a system
with an 8087?  (Also same question for 80286, V30, 80287.)

--henry schaffer

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[0364] ( 16 lines) bsilverio    02/14/86 13:21 ibmpc
Subject:RE:NEC V20 When 8087 is Used?
*(        from Multics ibmpc meeting on 02/13/86 )*

From: Doug Hall <hall%ittral.uucp@brl>
Date: 13 Sep 85 01:28:22 GMT


I am using the NEC V20 in my ITT Xtra (a little known but very nice
MS-DOS machine) with the 8087 co-processor. I have had no problems
with it. Anybody want to buy a used 8088? ;-)

Douglas Hall
ITT Telecom
Raleigh, NC
ittatc!ittral!hall

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Forum: p 340:342
[0340] ( 20 lines) bsilverio    02/14/86 13:18 ibmpc
Subject:RE:NEC V20
*(        from Multics ibmpc meeting on 02/13/86 )*

Date:  9 Sep 1985 10:06:32 PDT
From: Barry Megdal <[e-mail]>


Before everyone rushes out to replace their 8088's with NEC V20's:

I just replaced the 8 mhz 8088 in my Leading Edge, with the 8 mhz version
of the NEC V20.  It works fine, but the measured performance improvement
was 4% for a large assembly with the Microsoft Macro Assembler, and
10% for a CPU-bound Lotus 123 task (a large data fill).  Ok for $20 perhaps,
but hardly in the 25-100% range.  I am sure that test cases can be
constructed that will yield 25% and more, but what about real examples?
Or am I somehow seeing a different result due to the 8mhz part and/or
the Leading Edge?

-Barry

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[0341] ( 43 lines) bsilverio    02/14/86 13:19 ibmpc
Subject:RE:NEC V20
*(        from Multics ibmpc meeting on 02/13/86 )*

Date: Wed 11 Sep 85 11:07:17-EDT
From: Gern <[e-mail]>

I have a few comments on the NEC V20 'improved' 8088.

The NEC V20 is a CMOS IC that is pin and software compatible superset
of the Intel 8088.   Aside from the addition of extra instructions
(The Z-80 superset in the 8080 CP/M world haunts...), the NEC V20
has a separate ALU to calculate the address, instead of the Intel 8088
having to take extra clock cycles to reuse the 'core' ALU.   This
WILL give a significant increase in thruput.   The Intel 80186 and
Intel 80286 also use this separate address ALU.    HOPEFULLY, Intel
will come out with an 8088 pin compatible 80188.

NEC has been producing 8088 CPUs for some time now - AND THEY DO NOT
HAVE A LICENSE FROM INTEL TO DO SO (At least the last time I checked).
Downright illegal.   Even worse, these PIRATE NEC 8088s don't quite
work right, the 8087 support is messed up and won't work at all.  Do
note that AND, National (I think) ARE Licensed 8088 producers, and
a few companies (IBM being one) are licensed to produce 8088s for their
own use and products.

Now NEC has improved their stolen 8088 (and 8086, the NEC V30) with the
address ALU idea from the Intel 8018x.   Currently Intel is trying to sue
NEC and I hope that they win.   I also hope that Intel gets on the ball
and properly improves the 8088/8086 with a similar thruput increase.

Cheers,
Gern

[A longer version of this message appeared in INFO-HZ100. INFO-IBMPC
is limited to technical discussions of this chip. Hopefully we can
determine exactly what the differences are. BTW I have one installed
with an 8087 and haven't found any problems even though I use
floating point all the time. I am sure INFO-LEGAL (or is it law?)
would welcome a discussion of pirate hardware.  INFO-IBMPC doesn't
welcome such a discussion as these digests are too large already even
though I throw away 75% of the messages that arrive here. -wab]


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Forum: p 338
[0338] ( 21 lines) bsilverio    02/14/86 13:18 ibmpc
Subject:RE:NEC V20
*(        from Multics ibmpc meeting on 02/13/86 )*

Date: Sun 8 Sep 85 08:29:45-PDT
From: Steve Dennett <[e-mail]>


Well, I bought an NEC V20 from JDR Microdevices at the PC Faire last Friday.
Took it home and with some trepidation (felt like I was doing heart surgery
on my only child) put it into my Compaq transportable.

After everything was back together, I turned it on and began trying software.
So far no problems with any, including communications software (which often
seems to be sensitive to timing).  I haven't measured the speedup, but it
is noticeable; some of my old games are challenging again!  Not bad for
~$21.

Steve Dennett
[e-mail]


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Forum: p 291:293
[0291] ( 37 lines) bsilverio    02/14/86 13:10 ibmpc
Subject:NEC V20, V30 Replacements for Intel 8088/86
*(        from Multics ibmpc meeting on 02/13/86 )*

From: Bob Hartman <[e-mail]>
Date: 6 Sep 85 16:49:48 GMT
To:       [e-mail]


        To those of you that saw my posting last week about the new NEC V20
and V30 chips, thanks for responding and telling me where to get one.  I got
mine through JDR Microdevices ($20.95 - advertised in BYTE).

        As you may or may not know, the V20/V30 chips are 8088/86 look-alikes
that are sold by NEC.  The differences are many, but mainly in that the V20/30
are SUPERSETS of the 8088/86 family.  For example, they support 8080 emulation,
contain the 80186 instruction set, plus a bunch of new instructions.  The real
kicker is that the V20 is faster than the 8088 in most instructions, and the
rest of the instructions are at the same speed.  Big gains are in relative
addressing modes where the V20 takes 2 clock cycles for the address compared
to the 8088's 5-12 cycles.  Anyway, the moral of the story is that you can
buy this chip, stick it into your PC in place of the 8088, put the cover back
on, and everything will work as before.  The only difference is that you will
get a 5-100% improvement in performance depending upon the software being used!
I found that in general I was getting about 25% improvement.  For $20.95, you
can't beat this system upgrade.  I checked out every program I own (I run the
UN*X Gateway BBS - Fido 101/101, and I have about 20MB of programs), and they
all ran perfectly (and yes, that includes with and without an 8087 chip).  The
funny thing is that unlike the AT, programs that use the timer interrupt do not
run faster.  This is because the clock frequency is the same, just the
instructions execute faster.

Hope this helps people who were wondering.

- Bob Hartman -
UUCP: {decvax,ihnp4}!encore!vaxine!rch
BBS: Fido 101/101   -   [phone]   300/1200/2400 baud

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[0293] ( 11 lines) bsilverio    02/14/86 13:10 ibmpc
Subject:NEC V20
*(        from Multics ibmpc meeting on 02/13/86 )*

Date: Friday,  6 Sep 1985 13:10:05-PDT
From: [e-mail]  (David Dantowitz -- LTN2-2/H07)
To: [e-mail]


I am curious if anyone has tried the NEC V20 on Seequa's Chameleon
or any of the other IBM PC compatible.

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