thomas@eleazar.dartmouth.edu (Thomas Summerall) (10/05/89)
Hi Folks! It looks our deparment's Mac II is about to be released from memory bondage! I have in front of me a 68851 PMMU sent to us by Motorola. Here's the problem: I don't know if it is the right speed. Do PMMU's come in different speeds? If so, how do I know what speed this one is? I didn't specify 16Mhz in the request letter, so I'm not sure, and I don't want to fry my Mac in the process of installation... Thanks... Thomas Summerall thomas@eleazar.dartmouth.edu
jtwarden@pawl.rpi.edu (Joseph T. Warden) (10/06/89)
In <15944@dartvax.Dartmouth.EDU> thomas@eleazar.dartmouth.edu (Thomas Summerall) writes: > >Hi Folks! It looks our deparment's Mac II is about to be released from memory >bondage! I have in front of me a 68851 PMMU sent to us by Motorola. Here's the >problem: I don't know if it is the right speed. > >Do PMMU's come in different speeds? If so, how do I know what speed this one >is? I didn't specify 16Mhz in the request letter, so I'm not sure, and I don't >want to fry my Mac in the process of installation... > > >Thanks... >Thomas Summerall >thomas@eleazar.dartmouth.edu The designation for the speed is part of the part number for the chip as is stenciled on the top. You should see a list of numbers including (my memory fails me here) 16RC (or something like that). I also received a part from Motorola (Thanks so much Chet and crew) and it was a 16 MHz part. MacEnvy recognized its presence so I am assuming all is well. Caution - when installing (1) ground yourself and the Mac (2) wear a wrist strap (3) exercise great caution in removing the "dummy" PMMU and (4) make sure the PMMU is seated all the way in its socket (it does not go in easy - if you don't get it in your Mac won't boot!) - be careful not to touch the pins or bend them when inserting the PMMU. (If you know all of these cautions - my apologies; but I think it is best to be safe when dealing with static sensitive circuits). Good luck with your installation. Joseph Warden Rensselaer Polytechnic Institute
daveh@cbmvax.UUCP (Dave Haynie) (10/10/89)
in article <15944@dartvax.Dartmouth.EDU>, thomas@eleazar.dartmouth.edu (Thomas Summerall) says: > Do PMMU's come in different speeds? Yup. > If so, how do I know what speed this one is? Read the part. A 16MHz part will say something along the lines of MC68851RC16A ^^ This last part's the speed. The slowest 68020 family parts are 12MHz, the fastest 40MHz, though I don't know if MMUs are available in the full range of speeds. The part you need is 16MHz; a slightly faster part will usually work. -- Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Too much of everything is just enough