Re: 1 or 2 MHz interrupt on PC

From: Spiro Trikaliotis (Trik-news_at_gmx.de)
Date: 2001-05-08 12:59:48

Hi Nick,

> The speed limitation in this case seems to be reading from the I/O area on
a
> PC. This is because the bus slows down (for ISA at least). The best I've
> ever come across is approx 1MHz read rate from the I/O area on a PIII-600
> using 8bit accesses. I expect the limiting case is not much faster than
> this.

Ah, I forgot: I used 16 bit accesses for this purposes, because I needed
more than 8 inputs. Anyhow, if I remember right, 16 bit access are FASTER
than 8 bit access (at least, with all BIOSes I remember, the the wait states
for 8 bit access where more than for 16 bit accesses. I think that was
because 8 bit access must be compatible with even older hardware (from
pre-AT ages).

Spiro.

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