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Aucbvax.5619 fa.unix-wizards utzoo!decvax!ucbvax!unix-wizards Sun Dec 27 16:16:10 1981 VAX 750 disk controllers >From decvax!duke!unc!lynn@Berkeley Sun Dec 27 16:02:41 1981

We have two SI 9400 Unibus disk controllers on VAX 780's. I would not but them again. For about eight months we had endless problems finally fixed -- we were getting noise on the reset lines which would terminate transfers and also clear all error bits (and vv, and mol). After many board swaps (you thought DEC field service was bad that way!) the problems were finally fixed (probably noisy power supplies) but I would not be willing to go through that again. In addition, the SI controller does not keep up with the disk on a 780 -- I don't know about the 750. This is not a serious problem, as all file system transfers are fully buffered in the controller, but does cause some performance loss under heavy swapping.

I strongly recommend that you look at two other disk controllers -- the Western Peripherals DC-231 and the Emulex SC-21v. Both are single board Unibus controllers that are known to work on the VAX. Personally I think the DC-231 is a shade better, but I am biased -- I consult for Western Peripherals. (There is both Unix and VMS support for both controllers, by the way.) I think the Emulex is $5000 and the WP is $3500, but check it out.

You might also look at the Xylogics 650 -- they have an RM02 emulation and an RK07 emulation, which might be of interest if you plan to run VMS. (Software transparent, but not as nice a configuration.)

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