Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!ig!ames!oliveb!apple!vsi1!wyse!mips!mark
From: mark@mips.COM (Mark G. Johnson)
Newsgroups: comp.arch
Subject: Re: Do you have bandwidth?
Keywords: memory bandwidth latency
Message-ID: <18753@obiwan.mips.COM>
Date: 4 May 89 00:57:10 GMT
References: <407@bnr-fos.UUCP> <7766@thorin.cs.unc.edu> <23649@agate.BERKELEY.EDU> <833@wucs1.wustl.edu> <6759@cbmvax.UUCP>
Reply-To: mark@mips.COM (Mark G. Johnson)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 29

In article <6759@cbmvax.UUCP> jesup@cbmvax.UUCP (Randell Jesup) writes:
 >	But then again PGA's have thermal expansion coefficient problems
 >  due to mismatch with the coefficient of board they mount on (or so I
 >  was told).  That's why the RPM-40 in in a leadless chip carrier
 >  instead of a PGA.  (Perhaps PGA's with sufficient pins weren't
 >   rated for 40 MHz, either.)
 >Randell Jesup, Commodore Engineering {uunet|rutgers|allegra}!cbmvax!jesup


Seems to me that PGA's do just fine with respect to both temperature
and frequency.  The defacto industry-standard CMOS video DAC (Brooktree 458)
comes in an 84 pin PGA, dissipates 2.2 Watts, and runs at 125 MHz.
Maybe Brooktree is more clever with "rating" their package than RPM40 was.

Intel's i860 CMOS microprocessor comes in a 168-pin PGA, runs at 40 MHz,
and dissipates 3.5 Watts.  Maybe Intel .....

Hewlett-Packard's most recent HP-n000 series microprocessor, built in
NMOS, dissipates 26 Watts and is mounted in a 408 pin PGA.

Various ECL and GaAs RISC processors are about-to-be-introduced, from
several sources, dissipating godzilla amounts of power and running at mucho
Megahertz --- and several of them are in PGA packages.

Looks like folks who really want to, can make PGAs go quite far indeed.
-- 
 -- Mark Johnson	
 	MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086
	...!decwrl!mips!mark	(408) 991-0208