Jump to content

IIsi or IIfx ROM SIMM Markings?

Recommended Posts

Does anyone know how a IIsi ROM SIMM is marked on the SIMM itself? Or a IIfx ROM SIMM for that matter? I have seen this list with part numbers: http://home.earthlink.net/~gamba2/os8_se30.html#SIMM

but are these numbers on the SIMM itself?


All I know is that the IIsi ROM is a 256K, 64-pin, 4-chip SIMM. I'm looking for more info with which to identify them, say if some hypothetical person had a number of various ROM SIMMS pulled from various hypothetical systems but could not identify them (and the hypothetical suspense is killing me)! Perhaps someone has a close-up picture of one?


Thanks for any info!



Link to post
Share on other sites

Gamba gave the numbers that are printed on the individual ROM chips on the IIsi ROM SIMM (IC). He could have given you a part number or an IC number, but they have been misleading. Part number and IC number are silkscreened on the circuit board.


A circuit board can be fitted with different components, hence the separate IC and part numbers. This typically applies to video cards which may have more onboard VRAM, VRAM sockets or blank solder points on the board.


As far as Gamba and IIsi ROMs go: a IIsi ROM part number may have been misleading because if there had been a few IIsi ROMs. If in doubt, identify the components on the IC.

Link to post
Share on other sites
  • 68kMLA Supporter

You are almost always better off with the part numbers from the ROM chips, than you would be with the part numbers from the circuit boards, as Charlieman pointed out.


This is particularly apparent in the case of the Beige G3. OWC tried to compose a web page which would guide one to identifying the ROM revision of Beige G3 ROMs based on circuit board markings, but there are so many exceptions, it is nearly useless.


There are three revisions of the ROM chips, which all go in the same type of chip and those chips can go on any of the circuit board revisions. So the only association between ROM revision and circuit board revision is caused by overlaps in manufacturing dates.


Similarly, with the Macintosh II family ROM SIMMs (including the SE/30) the circuit board can be the same for all models. In every Mac II model which uses a ROM SIMM, the SIMM is a 64 pin SIMM which plugs into the same type of socket used by the IIfx RAM.


There are several SIMM ROM designs because Apple used several differently packaged ROM chips and so needed circuit boards for each type of chip which they wished to mount.


By the time of the IIfx Apple seems to have settled on the 32 pin PLCC chip for their ROMs.


Anyway, any time you wish to identify Apple ROMs, your best bet is to take the Apple part numbers off of the ROM chips themselves.

Link to post
Share on other sites
  • 1 year later...

Having my IIfx ROM SIMM in front of me:


4 ROM Chips labled with

KM23C101 0G-12


341$07.. 81 (82,83,84) different numbers on the Chips!

and a copyright by Apple 1990.


On the bottom under the Chips:


U1 U2 U3 U4


Its a "army dark" green card, 64-pinner

On the back side:




103 SM





This one was installed in my MacSE/30 - on the stratup it crates the SimasiMac for 5 seconds then starting the patched 8.1.


Sadly now after booting it up after a year it restarts often and shows the Simasi the hole time... welcome SimasiMac...


I try now my IIsi ROM SIMM because I heared that this one does not have the Simasi effect. I let you know about the results.

Link to post
Share on other sites

Gues what... Leaking Caps...


All capacitors where leaking but I could clean the board using spiritus alcohol and now it boots up nicely - I even get the screen jumping away :-)


But strange - the IIsi ROM did not boot the patched System 8.1 - there was NO Simasi effect as reported but after two seconds I got a blackMac with an Error Code (I did no remember the code...).


After re-adding the IIfx ROM SIMM I am back to Simasi for 3 seconds but after that MacOS 8.1 boots quite fast.


I will add the IIsi ROM back to see the Error Code again - maybe I get some more infos why the IIsi ROM did not work. Get back to you soon.

Link to post
Share on other sites

It turns out my IIsi ROM SIMM is an original MacSE/30 ROM SIMM?


The Error Code it produces is





I have´nt checked the meaning yet.


Because the ROM does not boot the system and is identical in the markings as the original SE/30 ROM SIMM I pulled out of my MacSE/30 maybe I bought an IIsi with a swaped ROM SIMM and I got the dirty ROM.


Does anyone have a ROM-SIMM from a Mac IIsi to check my version?


Edit - Thank you Gary - seems I do not have a IIsi ROM. To sad - but the IIfx ROM is running aswell.

Edited by Guest
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...