Subject: Re: silo overflow contd.
To: Jeremy Alan Green <>
From: Michael L. Hitch <>
List: amiga
Date: 10/20/1994 14:37:27
On Oct 20, 11:33am, Jeremy Alan Green wrote:
> Also, it seems that other people are getting better performance than I am
> with an A2000 and a GVP board.  My 2000 has a 50mhz 030 in it and it is
> unusable for transfering files off the net with ppp and ftp.  Is it
> something I am doing?  I was trying to download a 5 meg file, whilc should

  Is the GVP board an accelerator and SCSI interface?  Also, what's your
memory configuration?  If the accelerator includes the SCSI interface, then
the NetBSD SCSI driver should be doing DMA directly to the accelerator
memory.  If the GVP SCSI is a Zorro II board, it can only do DMA to 16 bit
memory.  NetBSD will try to allocate a DMA buffer from Zorro II memory, but
if there isn't any Zorro II memory, it will use chip memory.  Access to the
Zorro II memory is bad enough, but accessing chip memory is worse.  If the
GVP SCSI is doing DMA through a chip memory buffer, it is very likely to
cause a big hit in serial performance.  If the SCSI interface is on the
accelerator card, it should be able to use the on-board accelerator memory
directly, but may still cause problems with serial I/O.  There is a parameter
(_gtsc_maxdma) which will restrict the maximum DMA transfer length that
the GVP SCSI driver will do.  This could be binpatched to a small value
(i.e. 512, 258, or 128) to see if it helps any.  Using a smaller DMA
transfer length will decrease disk performance though.

  I would like to know what NetBSD reports when it configures your SCSI.
It should be printing out a dmamask value (which represents the valid DMA
address space), the address of the DMA buffer, and the maximum DMA length.

> to 230 minutes.  Is the serial hardware in the A2000 junk?  My mac which is
> a 16mhz 030 can handle 38.4 kbps with almost no problems...

  I'll bet the Macintosh doesn't have an unbuffered serial port.  I have
been able to transfer (using kermit) at 115K on the Amiga serial port -
on an A4000 with a 40Mhz Warp Engine.  I would get occasional silo overflow
messages, but very few.

  Oh, one other thing - which kernel are you running?  The latest one includes
some changes to the Amiga serial driver to deal with hardware flow control
better.  You are using CRTSCTS on your PPP link, aren't you?


Michael L. Hitch			INTERNET:
Computer Consultant
Office of Systems and Computing Services
Montana State University	Bozeman, MT	USA