14 Dec
2001
14 Dec
'01
3:28 p.m.
From: Richard Erlacher <edick(a)idcomm.com>
The 8250 was a fine chip for the application, though I wonder why they used
the
DIP version. There were better choices available, but
they didn't want to
lose
In 1981 there was only the DIP version as surface mount was not a widespread
technology yet.
the serial port board business by putting two of them
on the same card, and
by
that time serial I/O chips tended to have between 2 and
8 ports on them.
In 1981 they did exist, those with more than two ports didn't have second
source and they werent cheap. The 8274 ( the 8088 bus version of the
Zilog SIO) was about 4 times the cost of the 8250(in the fall of 1981)
though it was a far better part and intel would have loved the business.
What's funny is my Leading Edge Model D PC clone used 8251 and put all
the video, floppy, printer and COM1 on the mother board. In my book the
clones often {but, not always} improved a dumb design.
Allison
14 Dec
14 Dec
4:50 p.m.
I went with PLCC-44 in a couple of devices back in '81-82. The first ones I
used were the first application in which I put parts on both sides of the board.
The PLCC-68 was even more common, though many mfg's felt more comfortable with
the equivalent PGA. Most folks didn't like the relatively hot parts in a plastic
package. The 68-pin package was more common.
PLCC wasn't a "surface mount" device back in those days, being viewed as a
plastic version of PGA package. Lots of guys didn't like the gull-wing parts,
so they used the J-lead part in a socket. In most cases, the pinout of the PLCC
+ socket was the same as the equivalent PGA, if there was one.
Dick
----- Original Message -----
From: "Allison" <ajp166(a)bellatlantic.net>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, December 14, 2001 2:28 PM
Subject: Re: MITS 2SIO serial chip?
From: Richard Erlacher <edick(a)idcomm.com>
The 8250 was a fine chip for the application, though I wonder why they used
the
DIP version. There were better choices available,
but they didn't want to
lose
In 1981 there was only the DIP version as surface mount was not a widespread
technology yet.
the serial port board business by putting two of
them on the same card, and
by
that time serial I/O chips tended to have between
2 and 8 ports on them.
In 1981 they did exist, those with more than two ports didn't have second
source and they werent cheap. The 8274 ( the 8088 bus version of the
Zilog SIO) was about 4 times the cost of the 8250(in the fall of 1981)
though it was a far better part and intel would have loved the business.
What's funny is my Leading Edge Model D PC clone used 8251 and put all
the video, floppy, printer and COM1 on the mother board. In my book the
clones often {but, not always} improved a dumb design.
Allison
8428
days inactive
8428
days old
1 comments
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