Re: VAXstation 3100/30 KA420 SCSI DMA problem on netboot (and fix)

On Sun, Feb 18, 2024 at 11:59:30PM +0900, Izumi Tsutsui wrote:
> 
> Ok, this indicates:
> - No valid register at 200C00E0 (KA420_STC_MODE for KA420 to switch DMA size)
> - KA43_SC1_DADR/KA420_SCD_DADR (200C00A0),
>   KA43_SC1_DCNT/KA420_SCD_DCNT (200C00C0), and
>   KA43_SC1_DDIR/KA420_SCD_DDIR (200C00C4) are also available as KA420
> - There is some register is at 200C00B0
>   (no info at least in <machine/ka43.h>)

When I saw your reference to "200C00B0" I was curious and did a "Google"
search on "VAX 200C00B0".

The top item that came up was a bitsavers.org reference to "KA46 System
Board Specification" which pointed to this paragraph, for what it is
worth...

10.3.1 Register Definition

  The thirteen internal registers of the 53C94 SCSI Contoller chip are
  accessed as bits<07:00> of thirteen sequential longwords. Writes to
  the remaining bits of each longword are ignored, reads of those bits
  return UNPREDICTABLE data. The address range used by the 53C94 chip
  register set is 200C.0080 to 200C.00B0. In the following register
  description, only bits<5:2> of the address will be referenced.