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- Newsgroups: comp.sys.m68k
- Path: sparky!uunet!haven.umd.edu!darwin.sura.net!ftlsw.telematics.com!ted
- From: ted@telematics.com (Ted Goldblatt)
- Subject: Re: state of data bus during write of byte
- Message-ID: <1993Jan8.144915.28976@telematics.com>
- Sender: root@telematics.com
- Nntp-Posting-Host: sirius.ftlsw.telematics.com
- Organization: Telematics Intl., Inc.; Ft. Lauderdale, FL
- References: <C0HMG2.322@hermes.hrz.uni-bielefeld.de> <1ihk6gINNlve@uniwa.uwa.edu.au>
- Date: Fri, 8 Jan 1993 14:49:15 GMT
- Lines: 26
-
- In article <1ihk6gINNlve@uniwa.uwa.edu.au> john@gu.uwa.edu.au (John West) writes:
- >iikoch@techfak.uni-bielefeld.de (Ingolf Koch) writes:
- >
- >>What about other 680x0 (especially the 68040)?
- >
- >I think it copies the data onto all parts of the bus, but I can't find
- >the relevant bit in the book. Actually, I think it must, or the dynamic
- >bus sizing won't work.
-
- Moto must have forgotten to do this on the `040 - that's why
- dynamic bus sizing doesn't work :-).
-
- Actually, this is a :-(, since most systems need the dynamic bus
- sizer feature, at least for ROM references, and you're stuck
- either doing custom outboard logic or using the 68150, both of
- which "solutions" cost board real estate and prop delay.
-
- Question for Moto person: was dynamic bus sizing left out of the
- `040 due to transistor budget limits (or really, room for the
- "wires"), or because it was thought (at the time) that the
- feature wasn't really needed?
-
- ted
- --
- Ted Goldblatt ted@telematics.com (305) 351-4367
- Telematics Intl., Inc. Ft. Lauderdale, FL
-