Adaptec and DMA (long)

[Norman Kohn]

In article <9 at kaspar.UUCP> ires at kaspar.UUCP (Bruce R. Larson) writes:
>In article <1990Nov02.021739.9280 at ddsw1.MCS.COM>, nvk at ddsw1.MCS.COM (Norman Kohn) writes:
>> There have been many comments about boards that won't support
>> the Adaptec 1542[AB] SCSI bus master controller.
>i)   With all of the boards removed except the 1542B and a monochrone
>     video adapter, the monitor frequently refused to display anything
>     until the reset button was pressed a number of times.
>ii)  whether the monitor would work at all was influenced by the relative
>     positions of the video card and the host adapter.  In most config-
>     urations it just did not work.
>iii) The system would not even go through its memory test when the
>     serial/parallel card was present.  (No, there weren't any IRQ
>     or base i/o address conflicts.)
>
>These sound like timing problems to me.
>
>THE SOLUTION
>I remembered a posting in this group (thanks again guys) about
>possible problem when using the 1542B.  I replaced the 1542B with
>a 1542A and every problem vanished.  I discovered this last night,
I spoke with the technical person at the vendor who'd told me this.
He says that it's a characteristic of boards using the C&T chipset.
The 1542B holds the bus too long during its ROM boot-up.
Later buson/busoff are configurable in software (e.g., under ISC unix).
This is allegedly a matter of optimistic timing programmed into the
on-board ROM and could be solved with a ROM upgrade (fix).
Karl Deninger may be right that the motherboard could/should speak
up for itself.  I called Adaptec but have not heard back from
their technical people yet.

-- 
Norman Kohn   		| ...ddsw1!nvk
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