Screen artifacts with a IIfx ROM

[JDW]

...failing network filter and/or scsi controller? Have you tried replacing them?

Most of the information on the web and in Pina's books suggest replacement of the Bourns filter. But, no, I've not tried replacing that. If I had known-good replacement chips handy I would though!

But I wonder if a SCSI controller or new Bourns filters would in fact be a fix. I say this because I see the "strange artifacts" even if no SCSI drive is connected internally or externally, and even if no ADB or serial devices are connected. I would think the Mac would act up if one of those devices was attached and working through the controller, but unless the Mac polls those chips to see if they are okay, I again cannot see how replacing them would solve the problem.

Nevertheless, you are correct in saying that by not replacing them, you never know if the new parts would in fact be a fix.

Thanks.

 

[TylerEss]

I would be totally shocked if the SCSI controller replacement fixed it in any way, but the bournes filter is suspect, in my book...

I want to add that I have only ever seen the "strange artifacts" on a cold-boot; once an OS has been loaded and restarted, they have never occured.

They seem to occur less often now that I replaced the PRAM battery, too. I don't know if this is related or not.

 

[003]

I had discovered, that when I pulled the PRAM battery and booted with a non stock ROM, I never got any artifacts at all and the se/30 just booted normally.

 

[JDW]

Tyler, again, your experience is similar to mine. I only get them for a few short seconds at cold boot. I never see them any other time, even during a major system bomb. As to the PRAM battery having anything to do with it, I wrote a complete report about that in this Applefritter thread (the 4th post). Simply put, in my case, the PRAM battery and holder have nothing at all to do with it.

 

[JDW]

I see that the "strange artifacts" problem exists even on SE/30's currently being sold on EBAY. These artifacts are EXACTLY like mine, to the pixel. (Also note this AppleFritter thread and this AppleFritter thread supplement this thread in regards to these "strange artifacts.")

In light of all the well known CRT patterns documented by Larry Pina and others -- screen patterns that are always the same when hardware exhibits certain problems -- there absolutely MUST be a technical reason for the "strange artifacts." In other words, something clearly has gone awry on the logic board and/or analog board to cause these "strange artifacts," regardless of whether they cause me any noticeable trouble or not. Surprisingly, neither Pina nor anyone else on the web has ever documented the hardware reasons for the "strange artifacts."

And just to bring you all up to speed (without forcing you to read every single post in these threads about this), I see the "strange artifacts" only a cold boot, during the 60 seconds it takes my SE/30 to check all 128MB of RAM (and yes, if I put in less RAM, they still appear, albeit less than 60 seconds as it takes less time to check less RAM). When the RAM check concludes, the "strange artifacts" vanish and the normal "gray" backdrop and happy Mac icon appear as actually booting begins.

So many people have advised me to "just don't worry about it" -- but that is merely a cop-out to avoid saying "I don't know what causes them." But I want to know! What in the world causes these "strange artifacts"? And with Larry Pina having put such a comprehensive list of classic Mac CRT screen patterns in his books, why aren't the "strange patterns" in his books? I can only guess it is due to something that has taken 20 years to surface, which is something that Larry Pina would not have seen during the time his books are written. A real mystery, to be sure! And one I wish to solve!

Further speculation of a technical nature would be appreciated. Thanks.

 

[Charlieman]

And just to bring you all up to speed (without forcing you to read every single post in these threads about this), I see the "strange artifacts" only a cold boot, during the 60 seconds it takes my SE/30 to check all 128MB of RAM (and yes, if I put in less RAM, they still appear, albeit less than 60 seconds as it takes less time to check less RAM). When the RAM check concludes, the "strange artifacts" vanish and the normal "gray" backdrop and happy Mac icon appear as actually booting begins.

Haven't you just suggested the answer to your own question?

The SE/30 uses part of the system RAM for video, unlike the IIfx, so when you perform a cold boot with a IIfx ROM it will perform a full memory check. This memory check code has to be in the ROM (there is no OS at this point) but the IIfx ROM doesn't know that it shouldn't clobber the region used for video. After the OS starts to load, the system RAM used for video is protected from rogue activity and you see a normal screen again.

This is further supported by the fact that the artifacts only display on a cold boot and that their duration is linked to the length of the memory test. You may be able to confirm this theory by running a version of the Mac OS that allows you to disable the memory test on a cold boot.

The IIsi uses some system RAM as video RAM, but it requires more than a compact Mac. Additionally, it is likely that a different region of RAM is used for this purpose (the location should be in the developer notes or Inside Mac). So you should also get artifacts with a IIsi ROM, but they may be different.

 

[JDW]

Haven't you just suggested the answer to your own question?

In a word... "No." 8-o

(You would have had to read through this entire thread to see the reason why.)

...the IIfx ROM doesn't know...

Again, read through all the threads (this one and the 2 AppleFritter threads) I've linked for you in my previous post. That will eliminate my having to repeat things that have already been said, and it will bring you up to speed on the dozens of questions that others have asked me before (with my detailed answers). Nevertheless, I feel compelled to say this again...

The ROM is irrelevant to this problem (as is the "cleanliness" of the ROM connector contacts). Utterly and completely irrelevant. The "strange artifacts" occur even with the stock SE/30 ROM, (and yes, I've tried more than one stock SE/30 ROM too).