XT slots (was: RE: IBM 5161

From: Fred Cisin <cisin_at_xenosoft.com>
Date: Wed Apr 2 17:31:01 2003

Thank you for the details.

But could you explain (for those of us who barely know which end of a
soldering iron to hold), WHY did they do that? What did they gain by it?
What use is the difference?


On 2 Apr 2003, Steve Thatcher wrote:

> after checking in my IBM XT reference manual, the fact is that
> they added a buffer to the normal data and address bus and sent
> buffered these signals into J8. Also, they added a 14.318mhz
> oscillator on the expansion chassis side because they did not
> want pass this high of a frequency over the cable. This does
> mean that the manin 14mhz and the expansion chassis 14mhz are
> not in phase.
> The added buffers make the timning in slot 8 a littl emore tight
> because of the added delays through the additional chips. Slot
> 8 also had a requirement that it supply a card selected signal
> back to make sure the card was really ready to be accessed.
>
> The buffering from an engineering standpoint was done to increase
> the drive on the cable to the expansion chassis as well as help
> isolate the rest of the system bus from any added capacitance
> and noise from the outside world.
>
> best regards, Steve Thatcher
Received on Wed Apr 02 2003 - 17:31:01 BST