How can I access memory very fast over ISA bus?

How can I access memory over ISA bus very fast? I am read data
from the memory but this is really slow. I find out that
are 8 useless waitstates on the bus. What can I do to speed up
the access? I am use mmap_device_memory with no special options.


Bye Sascha( sascha@bitctrl.de )

Sascha Morgenstern
BitCtrl Systems GmbH
Weißenfelser Straße 67
Germany - 04229 Leipzig
Phon. +49 341 490 670
FAX. +49 341 490 67 15
eMail: sascha@bitctrl.de
WWW: http://www.bitctrl.de

Some BIOS gives you the option to removes some wait state ( at the
cost of running out of spec).

Try to read data in two bytes chunks to use the full with of the ISA
bus (if the card is 16 bit of course)

ISA bus is very slow compare to CPU ;-(

On Mon, 23 Apr 2001 12:53:22 +0200, “Sascha Morgenstern”
<sascha@bitctrl.de> wrote:

How can I access memory over ISA bus very fast? I am read data
from the memory but this is really slow. I find out that
are 8 useless waitstates on the bus. What can I do to speed up
the access? I am use mmap_device_memory with no special options.


Bye Sascha( > sascha@bitctrl.de > )

Sascha Morgenstern
BitCtrl Systems GmbH
Weißenfelser Straße 67
Germany - 04229 Leipzig
Phon. +49 341 490 670
FAX. +49 341 490 67 15
eMail: > sascha@bitctrl.de
WWW: > http://www.bitctrl.de
\

The words “ISA” and “FAST” should never be
used together in the same sentence.

You have basically two options:

  1. Do as Mario says and adjust your BIOS to remove
    the wait states. Upping the ISA clock may also help
    (i.e to PCIClk/3 rather than PCIClk/4). However,
    both of these options are pushing ISA out of spec.
  2. Redesign your hardware board to use bus master
    ISA transfers to memory – very ugly but possible.
    Ye olde Adaptec 1542 is a good example of this.

Michael Burkey

“Sascha Morgenstern” <sascha@bitctrl.de> wrote in message
news:9c11hp$9ce$1@inn.qnx.com

How can I access memory over ISA bus very fast? I am read data
from the memory but this is really slow. I find out that
are 8 useless waitstates on the bus. What can I do to speed up
the access? I am use mmap_device_memory with no special options.


Bye Sascha( > sascha@bitctrl.de > )

Sascha Morgenstern
BitCtrl Systems GmbH
Weißenfelser Straße 67
Germany - 04229 Leipzig
Phon. +49 341 490 670
FAX. +49 341 490 67 15
eMail: > sascha@bitctrl.de
WWW: > http://www.bitctrl.de
\