Date: Thu, 21 Aug 1997 10:54:43 -0600 From: "Justin T. Gibbs" <gibbs@plutotech.com> To: Tom Samplonius <tom@sdf.com> Cc: Andreas Klemm <andreas@wup.de>, Stephen McKay <syssgm@dtir.qld.gov.au>, freebsd-hardware@FreeBSD.ORG Subject: Re: Quiet SCSI disk? Message-ID: <199708211655.KAA20737@pluto.plutotech.com> In-Reply-To: Your message of "Thu, 21 Aug 1997 08:29:01 PDT." <Pine.BSF.3.95q.970821082249.9973D-100000@misery.sdf.com>
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> Beware. The ncr driver allocates up to 4 tags per device. The ahc >driver has a certain number of tags per channel (and it isn't easy to see >how many tags a device is using). This number is determined by the card >type. Most have 16 tags per channel (the 2940UW definitely has 16SCBs). >This number can be increased via paging the SCBs to system RAM. > > Adaptec has been cheapening their 2940 line. The original 2940 had 16 >SCBs, but newer cards only have 8. I think the only 2940 with 16 >SCBs is the 2940UW. Adaptec also made a 3940 with 255 SCBs, but newer >3940s also only have 16. Just to clear up any misconceptions: Chip # of SCBs # of slots in FIFOs paging #tags CAM paging #tags aic7770 4 4 N/A 255 aic7850 3 8 8 255 aic7860 3 8 8 255 aic7870 16 16 255 255 aic7880 16 16 255 255 Card Model Chip External SCB RAM 2940 aic7870 NO DISCONTINUED 2940W aic7870 NO DISCONTINUED 3940 aic7870 NO DISCONTINUED 3940W aic7870 NO DISCONTINUED 2940U aic7880 NO DISCONTINUED 2940UW aic7880 NO 3940U aic7880 NO 3940UW aic7880 NO 2940AU aic7860 NO 3980 aic7870 YES DISCONTINUED 3980W aic7870 YES DISCONTINUED 3980U aic7880 YES 3980UW aic7880 YES 3985 aic7870 YES DISCONTINUED 3985W aic7870 YES DISCONTINUED 3985U aic7880 YES 3985UW aic7880 YES Adapters with external SRAM can be configured to have 255 SCBs, but since I've never had access to a card to experiment with enabling this feature, the current aic7xxx driver does not support this mode. >Tom -- Justin T. Gibbs =========================================== FreeBSD: Turning PCs into workstations ===========================================
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