Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!think.com!yale!cs.yale.edu!cs.yale.edu!fischer-michael From: fischer-michael@cs.yale.edu (Michael Fischer) Newsgroups: comp.sys.atari.st.tech Subject: Re: ROM sockets in a Mega ST 2 Message-ID: <1991May1.163943.23932@cs.yale.edu> Date: 1 May 91 16:39:43 GMT References: <1991Apr29.083447.27132@bernina.ethz.ch> Sender: news@cs.yale.edu (Usenet News) Organization: Yale University Computer Science Dept., New Haven, CT 06520-2158 Lines: 34 Originator: fischer@ginkgo.CS.Yale.Edu Nntp-Posting-Host: ginkgo.theory.cs.yale.edu In article <1991Apr29.083447.27132@bernina.ethz.ch> felner@nessie.cs.id.ethz.ch (Tomas Felner) writes: >I want to upgrade a friend's Mega ST 2 from Blitter TOS to TOS 1.4. I have >never opened a Mega ST myself before, but I know that there are motherboards >for 2 ROM chips and others for 6 ROM chips (as in the old 520s). Last night >I opened his machine and I found 6 28-pin ROM sockets, labelled LO-0 to LO-2 >and HI-0 to HI-2. But there are only two ROMs in the sockets labelled LO-0 >and HI-0 !?!? I am confused, but I proceed and put 6 27256 EPROMS with TOS >1.4 in those 6 sockets. I boot, the screen turns white, the floppy light >flashes and the machine reboots and reboots and reboots ... > >Questions: > >Why are there 6 sockets if the ROMs only need 2? Or do I have both options, >2 and 6 ROM chips? If so, how do I change from one to the other? Is there a >jumper somewhere? I would prefer the 6 chips solution. If I have to stick with >2 chips, which EPROM type do I need? I found the same thing when I upgraded my Mega-4 to TOS 1.4 -- six sockets, the old ROM was on two chips and the new on six. Instructions that came with the new ROM told how to make the conversion. It involved removing a soldered-in chip and changing a jumper. I had my dealer do the work. He tried unsoldering the chip instead of simply clipping the pins and damaged the motherboard in the process. He finally patched things up and got it working, but I would never do it again unless there were absolutely no alternative. My recommendation: Take back the 6-chip TOS 1.4 ROM set and get the 2-chip set instead. Then you just plug them in in place of the old chips. -- ================================================== | Michael Fischer | ==================================================