Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!nstn.ns.ca!news.cs.indiana.edu!julius.cs.uiuc.edu!usc!samsung!interlan.InterLan.COM!interlan.interlan.com!dave From: dave@interlan.Interlan.COM (Dave Goldblatt) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: coprocessor... how fast??? Message-ID: Date: 28 Jan 91 20:25:32 GMT References: <1991Jan27.172506.15133@ncsuvx.ncsu.edu> <1991Jan28.150353.25420@athena.mit.edu> Sender: news@interlan.Interlan.COM (No News is BAD News) Reply-To: dave@interlan.interlan.com Organization: Racal InterLan, Inc., Boxborough, MA (1-800-LAN-TALK) Lines: 20 In-Reply-To: acook@athena.mit.edu's message of 28 Jan 91 15:03:53 GMT Nntp-Posting-Host: slam.interlan.com According to the Intel spec book I looked at, the 80287 (and, I assume, the 80387; not sure about the 8087) can be driver either off an external clock, or, as is usually the case, off the system clock. When driven off of the system clock, the coprocessor uses an internal divide-by-3 to knock down the system clock speed. Thus, if your 80287 runs at 6MHz, the system clock can be no greater than 18MHz. The problem is that some people refer to say, an 80287-8 to mean an internal clock of 8MHz, whereas others mean that it will only work on an 8MHz machine. Best bet is to talk to the manufacturer (or look in the data books) to verify EXACTLY which coprocessor you'll need. -dg- -- "Dan Rather? NOT!" * Dave Goldblatt [dave@interlan.com] - Wayne Campbell, * Diagnostic Engineering "Wayne's World" * Racal InterLan _SNL_ * Boxborough MA (508) 263-9929