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8086 uP Require

J

Jim Thompson

Jan 1, 1970
0
Winfield Hill wrote...

Unlike some of the right-wing advocates here on s.e.d., I'm not one
to see things in black and white.

Oh, BARF! Gray is for political hacks... black and white is for
engineering.
While faster ram memory might help
solve WayneL's problem, it's also possible slower memory might be the
solution. That's because some slow memory ICs will store the data-bus
contents 50's of nanoseconds before the end of the WR* strobe pulse.
Slow memory tends to have a longer data-change setup time. In some
designs, slow RAM available when the design was tested might have led
to an unworthy confidence. Later on, new, faster RAM can destroy the
design's safety margins, and render late production a fragile product.
As in so many issues, the precise details determine the exact answer.

Modern designs could potentially suffer from these same issues, but
many employ a power solution, that wasn't available in the old days.

Good design does NOT rely on set-up-and-hold times as part of the
system timing.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

Global Warming is God's gift to the Blue States ;-)
 
W

Winfield Hill

Jan 1, 1970
0
Jim Thompson wrote...
Good design does NOT rely on set-up-and-hold times as part
of the system timing.

Agreed. We're talking about designs > 20 years ago, made with
limited resources. Unfortunately many such designs did not
bite the bullet and add the extra fast buffer chips necessary
for proper safe synchronous designs. I did many bullet-proof
synchronous designs in the mid 70s. So I'd say, while there
may not have been sufficient excuse for taking the cheap way
out in the mid 80s, I know it was commonplace. If you look at
Intel and other app notes of the day, you'll see it was common.
 
P

Pooh Bear

Jan 1, 1970
0
Winfield said:
Kryten wrote...

It would be great if it would solve his problem!

If it doesn't, I wonder how an NEC V30 would fare ?

Graham
 
P

Pooh Bear

Jan 1, 1970
0
Winfield said:
Jim Thompson wrote...

Agreed. We're talking about designs > 20 years ago, made with
limited resources. Unfortunately many such designs did not
bite the bullet and add the extra fast buffer chips necessary
for proper safe synchronous designs. I did many bullet-proof
synchronous designs in the mid 70s. So I'd say, while there
may not have been sufficient excuse for taking the cheap way
out in the mid 80s, I know it was commonplace. If you look at
Intel and other app notes of the day, you'll see it was common.

I recall doing some work for a marine radar company that made its own
8086 based boards for anti-collision systems.

One in 10 or so simply never worked they said.

Graham
 
M

Michael A. Terrell

Jan 1, 1970
0
Pooh said:
If it doesn't, I wonder how an NEC V30 would fare ?

Graham


Weren't the NEC chips upgrades for the 8088? I know the V20 was.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
M

Michael A. Terrell

Jan 1, 1970
0
Christian said:
As the V20 was an 8088 replacement, so the V30 was an 8086 replacement:

<http://www.cpu-world.com/CPUs/V30/>

// Christian Brunschen



Thanks, I had never used the V30 and I couldn't remember the V30
specs.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
P

Pooh Bear

Jan 1, 1970
0
Michael A. Terrell said:
Weren't the NEC chips upgrades for the 8088? I know the V20 was.

They were indeed. That means some timings are likely to be different but
that might work in the OP's favour since we don't know the reason for his
display issue.

Graham
 
R

Rich Grise

Jan 1, 1970
0
They were indeed. That means some timings are likely to be different but
that might work in the OP's favour since we don't know the reason for his
display issue.

Graham

No, it means it's useless in an 8086 socket - they have different data
busses. But I had thought that the V30 was just a hot V20, and the V40
was the 16-bit one, or am I thinking 286?

Thanks,
Rich
 
P

Pooh Bear

Jan 1, 1970
0
Rich said:
No, it means it's useless in an 8086 socket - they have different data
busses. But I had thought that the V30 was just a hot V20, and the V40
was the 16-bit one, or am I thinking 286?

The V30 is a drop-in replacement for an 8086. I fited one in my Amstrad PC of
old. It does the sums faster !

Graham
 
An 8088 is perfectly useless in an app that calls for an 8086. The core is
the same, but the 8086 has an actual 16-bit data bus, where the 8088 has
only an 8 bit bus, and doubles up on memory/peripheral access.

IIRC, from reading a useless old IBM PC handbook (written in '81ish
and very useful, but this was in about '94. Stupid library, stupid
council / government fucking budget cuts to give tax bribes to their
rich mates etc etc etc).

But any, IIRC, it was the address bus that also doubled (was
multiplexed) with the data bus.

The 8086 had it's 20 address lines, the lower 16 of which were D15..D0
.. On the 8088 only the bottom 8 addr lines were D7...D0. Pin-wise
there's no saving, IIRC there's some pin on the chip that tells you
whether the bus has address or data on it.

The IO was obviously multiplexed into the memory range, same as the
Z80, same as practically every CPU I can think of. Don't even Pentiums
use the same addr/data and an IORQ/MEMRQ pin (or possibly 40 of each
to handle the current demands. Next year's big computer comes with
optional PSU / arc welder)?

Anyway... it was really a good idea. Save a damn fortune on excess
glue and RAM, use existing, popular support chips, and still enjoy
16-BIT POWER!!!! (To quote the Sega Megadrive, 10 years or so later).

Actually a lot of early 80s arcade games used an 8086. Tho Bubble
Bobble, in about 1985, used 3 Z80s. At the time, as a product of price
and power, it was a brilliant idea. Just god-awful to program.
Fortunately we're just about over that legacy.
 
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