3 Nov
2005
3 Nov
'05
3:45 p.m.
Subject: Re: That darn Intel jingle...
From: "Chuck Guzis" <cclist at sydex.com>
Date: Thu, 03 Nov 2005 15:32:44 -0800
To: cctalk at classiccmp.org
On 11/3/2005 at 6:22 PM ard at p850ug1.demon.co.uk wrote:
Z80 PIO.
However the 8255 is of the 8080/8085/z80/ and general Intel lineup and
due to that also the most widely multiply sourced. It's ugly but what
comes in to do better?
The worst, by far, has to tbe the 8255 parallel
chip. That was clearly
designed by soembody who didn't think what he was doing. For those of you
who've not read the data sheets, any write to the mode control register
clears all output port lines to 0.
For what it is and WHEN it was developed, the 8255 is a pretty good device.
There are still new products made that use it (very popular in the data
acquisition area). I can't think of any other single parallel interface
chip from the 70's that's still puffing along. I wish the thing was faster. The NEC 82C55AC variant
is good to 10 Mhz,
but that's pretty slow when you're talking about a PCI bus.
D72055 the last version of the part hit 12mhz. If your going on PCI
why bother and just put a gate array to work.
There are precious few of the really good peripheral
chips from the early
days of the microprocessor that are still as useful. The Signetics 2651
USART, maybe?
Well there are plenty of 8251, 8253, 8259 around, then there are the 2681s
and (gag) 8250 series.
Not many but then what do you need after lots of ram?
Allison