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Re: OT: Mac Plus and 20SC
- Subject: Re: OT: Mac Plus and 20SC
- From: Salvador Limones <sallimones@hotmail.com>
- Date: Wed, 24 Dec 2003 05:19:11 GMT
- Newsgroups: comp.sys.apple2
- Organization: LSA
- References: <chZrb.8386$lK1.7418@news04.bloor.is.net.cable.rogers.com> <tjJDb.193924$e6.7314449@twister2.libero.it> <r6LDb.194232$e6.7330250@twister2.libero.it> <w0NDb.22058$OJ.17883@edtnps84> <ruSdnRdN_fzWMEKiRVn-sA@comcast.com> <_3SDb.2$Lu1.1@edtnps84> <4LydnRIGL5T0l32i4p2dnA@comcast.com> <tsUDb.94838$bC.75123@clgrps13>
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Last week I bought"FWB's Guide To Storage" by Norman Fong. Along with
the other stuff, the author mentions several problems with the original
Plus:
1. "The Plus cannot properly handle the SCSI Req/Ack handshaking
protocol because it has no hardware line for relaying handshaking or
interrupts."
The handshaking is being performed in software (by the drivers) and is
very slow. The Mac SE and later have hardware handshaking.
My comment: Every considerably "modern" HD is too fast for the Plus.
2. "The Mac Plus does not include internal termination because it has no
internal SCSI connector. According to Apple, the devices closest to and
farthest away from the Macintosh Plus should be terminated. But if there
is only one peripheral attached to the Plus, only that device needs a
terminator.
Alex