Re: ISA-Bus load?

Matti E Aarnio (
Wed, 3 Jul 1996 16:36:36 +0300 (EET DST)

> I am wondering if there is a chance to get an idea of what is
> happening on the PC's ISA-Bus from a programmer's view.
> I have a couple of add-on cards providing my software with
> datastreams from the real world, data rates less than 500kbit/s - I
> would like to plug in as many of them as possible.
> All I would like to find out is where the limit is. The idea
> of just trying it out is probably less than semi-optimal - who knows
> how good may way of communicating with the hardware is?
> I was hoping to find anything in the /proc-fs - in vain it seems.
> There must be something in the kernel...
> Thanks for any hints!!

With the ISA-bus you can do about 2 million memory
or io-cycles per second (depending on your bus-clock
setup -- from bios setups). There is nothing the
programmer can do in his/her programs -- except to
avoid any extra references via the ISA-bus.

The ISA-bus is SLOW! Compare to 120 MB/s on PCI with
30 MHz burst clock, and 4 byte wide transfers..

> Volker

/Matti Aarnio <>