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| complex instruction set compiler vjain@ececs.uc.edu (Vipin Jain) (1998-03-15) |
| Re: complex instruction set compiler ian@five-d.com (1998-03-15) |
| Re: complex instruction set compiler chase@naturalbridge.com (David Chase) (1998-03-15) |
| Re: complex instruction set compiler Eric.Hildum@Japan.NCR.COM (Eric Hildum) (1998-03-18) |
| Re: complex instruction set compiler richard@cogsci.ed.ac.uk (1998-03-18) |
| Re: complex instruction set compiler tmoog@mcs.net (Tom Moog) (1998-03-20) |
| Re: complex instruction set compiler jan@mailhost.neuroinformatik.ruhr-uni-bochum.de (Jan Vorbrueggen) (1998-03-20) |
| From: | Jan Vorbrueggen <jan@mailhost.neuroinformatik.ruhr-uni-bochum.de> |
| Newsgroups: | comp.compilers,comp.arch,comp.compilers.tools.pccts |
| Date: | 20 Mar 1998 01:19:09 -0500 |
| Organization: | Institut fuer Neuroinformatik, Ruhr-Universitaet Bochum, Germany |
| References: | 98-03-144 98-03-149 98-03-175 |
| Keywords: | architecture, performance |
Eric Hildum <Eric.Hildum@Japan.NCR.COM> writes:
> The backup program used the CRC instruction - in fact, removing CRC from the
> HW in the uVAX I and II was considered a mistake at the time because of the
> dramatic effect on backup time requirements when the backup default was /CRC.
> [I can believe that EDIT helped; it was one of the few CISC instructions
> in the IBM 360 architecture. But depending on a CRC instruction was pretty
> silly since you can do CRC so easily with a small precomputed table and
> a few shifts and masks per byte. -John]
Indeed, after the slowdown from emulating CRC in the microvaxes was noted,
BACKUP was modified to compute the CRC as noted by John, and ran faster even
on those implementation that had the CRC in hardware. One of the best
demonstrations of RIS{C|K}...
Jan
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