Date: Sun, 3 May 1998 19:49:22 +0200 (SAT) From: John Hay <jhay@mikom.csir.co.za> To: phk@critter.freebsd.dk (Poul-Henning Kamp) Cc: freebsd-bugs@FreeBSD.ORG Subject: Re: i386/5398 Message-ID: <199805031749.TAA07478@zibbi.mikom.csir.co.za> In-Reply-To: <11689.894214766@critter.freebsd.dk> from Poul-Henning Kamp at "May 3, 98 06:59:26 pm"
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> > How is XFree86, a userland program, able to disable interrupts ? > > The Hardware blitter/PCI latency also seems impossible, 115200 = > > 11.5 KBytes/sec = 86uS per character x the FIFO depth (after the hack) > > of 4 or 8 character times is over 500uS. It just doesn't make any > > sense. > > By monopolizing the PCI bus, while blitting 3 or 4 MB data, I can > certainly see PCI starvation. Remeber that to blt 3 MB around, you > have to read 3 MB and write 3MB, so that is 6MB over a 133MB/sec bus, > giving a minimum duration of 45 msec per blt. Just to get my understanding of the hardware a little better. Is this blitting just doing something like a software memory copy, like what the C function bcopy() does? And can that really block interrupts just because it is done over the PCI bus? Or does blitting use something different? John -- John Hay -- John.Hay@mikom.csir.co.za To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
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