Yes, but even at 50 cents per hour, it's less costly to replace the board by
snagging one from a thrift store for $1 than to set about to repair one. The
thrift stores discard them by the dozens every day. So long as they are
cheaper to buy than to fix, I'd suggest one do that. It's only a matter of
time, however, before the CPU, memory, I/O and everything else you'd want will
be on a single device. That will help with the packaging, but won't do much
for maintainablity.
I just finished trying to buy some 3-volt logic, and find that everybody in
distribution's convinced that the only thing that is relevant any longer is
1.5-volt logic. I must have blinked ...
Dick
----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, March 13, 2002 3:51 PM
Subject: Re: Free: older hardware, mainly PC
> >
> > At 05:43 PM 3/12/02 -0500, you wrote:
> > >Also, surface mount
> > >chips would be hard, since they are usually so small, although, I don't
> > >think uarts are made that way, none that I've noticed any way.
>
> Oh yes, many common UARTs (and other serial chips) are available in PLCC
> packages that can be surface-mounted. That does not make them
> non-replaceable, though...
>
> > >
> > >Chad Fernandez
> > >Michigan, USA
> >
> > Yes they are; most recent i/o cards have everything (decode logic,
> > buffers, UARTs, even line drivers/receivers) integrated
> > in a small SMC chip. Toss and replace. I like old serial
>
> Painful, aren't they :-(
>
> However, the original message said '16450 UARTs'. To me (as a hardware
> hacker) that's a particular chip, often a 40 pin DIL device (although I
> think a PLCC version exists). Single UART, no FIFO.
>
> A multi-I/O chip (or even a dual UART) that happens to be
> software-compatible with a 16450 is _not_ a 16450 to me.
>
> > cards with jumpers, even if they have soldered UARTS and
> > drivers, because I can fix them and upgrade them. Plus, they're
> > usually double-sided and easy to work with.
>
> Having replaced transistors on an irreplaceable, irrepairable [1] 16
> layers PCB, I don't generally worry about normal multi-layer board any more.
>
> [1] On-topic, very. The main ROM board from an HP9100B. The ROM assembly
> is 4 boards linked by soldered-in pins. Address decoder, 2 sense
> amplifiers, and the ROM itself. The last contains driver transistors and
> an inductively-coupled matrix of tracks that form the bit pattern in the
> ROM. If that ever fails there's no easy way to repair it. Fortunately all
> I've had to do is replace the odd driver transistor.
>
> -tony
>
>
Received on Wed Mar 13 2002 - 18:52:36 GMT