Mac Plus RAM upgrade

[MacDougall]

Hello, new Mac tinkerer here. I have a Mac plus which is nearly fully operational. I have put the machine back to 1mb for now while I try to sort some other problems, but I have a few questions about upgrading the RAM.

Is it normal for a Mac plus with 4Mb to take a long time to start up?

After the bong, this Mac plus will sit with a grey screen for quite a while before asking for a disk or booting an HD.

Once going, it seems to be very happy with the 4Mb. Is there a recommended memtest program?

How picky should I expect the machine to be regarding simms, I have four 4Mb sets, (all parity), but only one seems to work properly. I've seen checkerboards and garbage and nothing at all with the others. Is it always required to readjust the voltage after upgrading RAM?

 

[Macdrone]

The issue should be the resistor on the motherboard should be removed. If it works with one set of 4 then I would guess it already is. Mine doesn't take a long time to boot, but capacitors may be dying slowly on the motherboard. Also the ram you have may be bad. I've been finding more and more go bad. Even uniserver will tell you I sent him some on a motherboard that just were garbage that worked before I sent to him.

 

[MacDougall]

Yep I did the resistor thing. I have also replaced all the electrolytics so it isn't old caps. There is a lingering problem on the analogue board at startup so I have put it back to 1Mb for now. I just wondered if this was normal. If it isn't clear, it doesn't take ages, just a chunk longer than with 1Mb, about what I might expect if there was a memory test at cold boot. If I press the reset button, the delay doesn't happen again.

The memory could be bad, it was thoroughly tested on a PC but they have been in storage for about 4 years since then.

 

[Macdrone]

Oh yeah it will take longer, So you will have a longer boot, new battery may help that also so it remembers it does a mem test. If other ram causes an issue that probably means a stick of it has gone bad. Wish I could tell you a good way to lck that down, but I am looking for a 30 pin mem test unit for cheap myself lol. As one of those can tell size also.

 

[onlyonemac]

Is it normal for a Mac plus with 4Mb to take a long time to start up? After the bong, this Mac plus will sit with a grey screen for quite a while before asking for a disk or booting an HD.

Those are really one in the same "problem". Actually, there's no problem at all! The grey screen means it's checking out its memory-the more memory you've got, the longer this will take.

 

[MacDougall]

Thanks, that's what I was hoping. How about the voltage. At one point I had checkerboard with the RAM which then worked after an adjustment. Is this normal or may indicate a PSU problem?

 

[Charlieman]

I presume that your working configuration uses 8 or 9 chip SIMMs. High density two or three chip SIMMs will cause checkerboards or random crashes. Different SIMM sets may have varying power consumption but not normally sufficient to require psu adjustment.

To improve startup times for the Plus, ensure that any SCSI boot disk has a high ID (ID six descending) if possible.

 

[onlyonemac]

At one point I had checkerboard with the RAM which then worked after an adjustment. Is this normal or may indicate a PSU problem?

Right. From what I've heard, the adjustment will only fix the problem temporarily. What's needed now is to replace all the capicators on (or "recap") the analogue board. If that doesn't help, then do the PSU, and then if that doesn't help then do the logic board. Adjusting the voltage will only fix the problem temporarily, as the capicitors will continue to get worse-therefore making the problem reuturn.
BTW If you're not comfortable doing the job yourself, then send it over to uniserver.

 

[volvo242gt]

The 68000 machines take a while to do their memory test. My 512Ke didn't take very long, since it was only 512k. But, my Plus (swapped the Plus board and shell over to the 512Ke's chassis, so I could use it, since the analog board has issues on the Plus' chassis) takes a while. As do both of my SE's. All three of them are maxed out, RAM-wise.

-J

 

[tomlee59]

Don't worry about the checkerboard pattern if it always goes away. Unlike later models, the Plus analog board doesn't have a congenital problem with caps, so this recapping business is not the first thing to consider here.

The memory test is indeed causing the extended boot time. If you're impatient like me, and don't want to wait, boot with the mouse button held down. That bypasses the memory test altogether. You can release the button as soon as you see it enter the normal boot sequence.

 

[MacDougall]

Thanks for all the advice, seems like this is nothing to worry about. I'm having another go at this mac at the moment and will open a new thread about that startup problem.

 

[nvdeynde]

Use 8 or 9-chip ram modules only in Compact Macs. They are the safest bet.

In some models, the 2 or 3-chip modules work but they often cause a lot of problems.

From personal experience 2 and 3-chip modules often give issues on Plus and SE boards going from not posting to being instable.

 

[MacDougall]

All four sets I have are 9 chip. Does seem odd that only one set works but once it is going it seems to work perfectly. Maybe just had bad contacts or a faulty simm with the other sets. I'll try this again if/when I'm satisfied everything else is in order.

 

[nvdeynde]

Are these matched sets of 4x identical modules ?

Mixing different modules with different speed or other chips in the same ram bank often gives unpredictable results.

The longer boot time with 4MB is normal, however it's not taking minutes, about 20 to 30 seconds I suppose.

If you have an unstable system and the rams are known good, then recapping of the logic board and the Analog board is definately a good idea, certainly if you want to use the machine regularly.

You could run ProVue ramtest on your Mac Plus for 12 hours to exclude ram problems, however if the machine is not recapped yet, It may not last this long.

What voltages do you get at the +5, +12v and -12v lines measured through the external FDD connector ?