felner@nessie.cs.id.ethz.ch (Tomas Felner) (04/29/91)
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?
The revision number of the motherboard is 5.0. The machine is about 2-3
years old.
Tomas Felner
--
Tomas Felner, Quellenstrasse 30, CH-8005 Zurich, Switzerland
email: felner@nessie.cs.id.ethz.ch, felner@iiic.ethz.ch
for C hackers: #include <std_disclaimer.h>
for Modula-2 programmers: FROM Standards IMPORT Disclaimer;ytsuji@wucc.waseda.ac.jp (Y.Tsuji) (04/29/91)
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 ST2 to TOS 1.4. (deleted) > Questions: > > Why are there 6 sockets if the ROMs only need 2? So that 6 new ROMs can be placed. > Or do I have both options, Yes, you do. > 2 and 6 ROM chips? If so, how do I change from one to the other? Is there a > jumper somewhere? 6 ROMs are 256 stuff while 2 ROMs are 1 megabit stuff. You must 'short' pin 2 and 12 of U12 (pluck off the IC first and replace a socket so that future TOS can be fitted in 2 chips.) As for jumpers w2 and w3, replace the caps the other way. > I would prefer the 6 chips solution. If I have to stick with > 2 chips, which EPROM type do I need? The same type you have had of course. The Best Electronics of San Jose sell a plug-in board by Wizztronics that looks after two different sets of ROMs( 2 and 2, 2 and 6, or 6 and 6 chips) for $69.95. It will allow you to switch between to different OSes. I haven't tried it but I can well imagine it.
fischer-michael@cs.yale.edu (Michael Fischer) (05/01/91)
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 <fischer-michael@cs.yale.edu> | ==================================================
fischer-michael@cs.yale.edu (Michael Fischer) (05/01/91)
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 ... When I replied to your posting, I didn't notice that you were talking about "EPROMS with TOS 1.4". I know that Atari distributed early copies of TOS 1.4 on EPROMS but later switched to ordinary ROMS. I do not know if TOS 1.4 is legally available any more on EPROMS, but if the EPROMS that you have are not legal copies, then I do not condone what you are doing. -- ================================================== | Michael Fischer <fischer-michael@cs.yale.edu> | ==================================================