LC II vs. 4MB SIMM Problem

Genjoke

Tinkerer
Oct 31, 2021
72
43
18
Brazil - Rio de Janeiro - Flamengo
Hi folks.

My first color mac was a 2nd hand LCII I got back in 1995.

A couple years ago I got a new LC II. I got it all the way from France to Brazil, hence I cal him Frenchy (my language has gramatical gender and computers are masculine lol).

I am little by little upgrading it to the dream machine from my youth. It has now:
  1. FPU - I soldered the socket and added a 16MHz 68882
  2. 512k VRAM
  3. Blue SCSI
  4. SC-88 MIDI
  5. Assanté SCSI-Ethernet networking (the real deal, not emulated)
I had some 4MB SIMMS but I decided to put them on My Classic II, leaving Frenchy with only 2MB (2x1MM) of extra memory.
Recently (In fact it got here today) I got an Apple Ethernet LC Card and an extra pair of 30 pin 4MB SIMMs.

Here comes the problem: When I install the RAM and start with Extensions Off, I get the 10MB of ram (4 soldered + 8 installed - 2 not addressed). However, if I turn on extensions there's no way it will successfuly boot! I get either:
  • Freeze during startup before any extension icon is displayed in the bottom of the screen
  • Illigal instruction
  • Sad Mac (0000000F / 00007FFF)
I didn't try to install the Ethernet LC Card yet.

I tried even removing the FPU, to no vail. I also tried to boot from 3 different disk images, using system 7.1.2 or 7.5.5. Both started up ok with Extensions Off but could not boot properly when extensions were enabled.

Another symptom: when booted with extensions off and left running with 10MB, I noticed some video artifacts. Tiny pink dots in rows across the screen, very few, but they are there.

Do I have wrong SIMMs? In fact I bought them from a fellow collector who removed them from an IBM 386. They are 9 chips SIMMs.

VRAM Issue (due to the artifacts)?

Do I have any other issue?

Any suggestions?

As always thanks for any help.
 
Last edited: