Date: Tue, 25 Jan 2000 21:53:37 -0500 (EST) From: Ralph Strohschein <ralph@tinynet.hamilton.on.ca> To: freebsd-questions@freebsd.org Subject: Adaptec 1542CF and More Than 16 MB Ram Message-ID: <Pine.BSF.3.96.1000125193146.12974A-100000@starlight.tinynet.hamilton.on.ca>
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My apologies if this should be directed to the SCSI mailing list instead. I'm running FreeBSD 3.4-RC on a pentium 75 system with 16 MB ram, an adaptec 1542CF, two SCSI-2 disks, a SCSI DAT, and a SCSI cdrom. My system seems to thrash the disks a lot (mainly while expunging messages in Pine when I have several hundred messages in my inbox). I have softupdates enabled, so I would presume this thrashing is due to paging. I'm thinking of increasing the ram to 32 MB. What is not clear to me is how the aha driver handles DMA and more than 16 MB of ram. I do recall that bounce buffers were dropped after FreeBSD 2.2.8. Am I to assume that DMA will no longer work if I increase my ram? (I'm assuming that the busmastering capabilities of this card are enabled for 16 MB or less in 3.X ??). Will I be stuck with PIO mode, or will it only resort to PIO mode when copying to memory locations above 16 MB? Should I upgrade the ram, or would I be better off upgrading to a busmastering PCI adapter first? -- Ralph Strohschein ralph@tinynet.hamilton.on.ca To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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