CompuAdd 433 RAM upgrade (+CMOS battery question)

[smeezekitty]

So as you may know from the other thread, I am currently working on a CompuAdd 433 486 machine.

It is working well so far, but I am planning on booting Linux on it in addition to DOS/Win3.1

8 MB RAM is just barely enough to boot Linux and not enough to do anything useful.
I would like to get it up to atleast 12MB RAM with 16+ being better.

The motherboard has 12 RAM slots, of which there is current 8x1 MB 30-pin parity RAM sticks installed. As I understand, I need to install RAM sticks in multiples of 4, correct?

Does anyone know the maximum RAM on this board? Could I install 4 of these: http://www.oempcworld.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=018781&AttributeCode[1]=Computer&gdftrk=gdfV24137_a_7c1396_a_7c4928_a_7c018781&gclid=CKG7nNn5qLkCFcdxQgodhWwAUA to get 24 MB?

Another thing is the CMOS battery is bad and it loses all the settings within 4 hours of being off. Its external so easy to replace but I don't know the voltage and if it is rechargeable or not.

Thanks in advanced

 

[High_Treason]

I don't know anything about this machine, the maximum RAM is probably chipset dependant. Most 486's will take 16MB no problem, though some OEMs are weird about things like that. Also the ram you link to has parity, some boards use it, others ignore it but sometimes you get one that refuses to run with it.

You might be able to put a multimeter accross the terminals for the battery and fire the system up, should give you an idea of the voltage and if there's a sudden increase once the machine is running the battery is likely rechargeable in which case installing a new one will require adding a diode between the new battery and the board if they are of a different type.

 

[smeezekitty]

Thanks for the reply.

I don't know anything about this machine, the maximum RAM is probably chipset dependant. Most 486's will take 16MB no problem, though some OEMs are weird about things like that. Also the ram you link to has parity, some boards use it, others ignore it but sometimes you get one that refuses to run with it.

I googled the numbers on the existing sticks and appears that all the sticks currently in it are parity RAM so I figured I should stick with that.
Unfortunately I have know way of knowing the chipset because I cannot find a model number on the board and there is very little on this machine online.

You might be able to put a multimeter accross the terminals for the battery and fire the system up, should give you an idea of the voltage and if there's a sudden increase once the machine is running the battery is likely rechargeable in which case installing a new one will require adding a diode between the new battery and the board if they are of a different type.

Ok I will get the meter out when I get a chance

Do I just install new sticks? Or do I have to mess with jumpers or something for RAM?

 

[modem7]

Another thing is the CMOS battery is bad and it loses all the settings within 4 hours of being off. Its external so easy to replace but I don't know the voltage and if it is rechargeable or not.

What are the markings on the existing battery ?

Do I just install new sticks? Or do I have to mess with jumpers or something for RAM?

Different motherboards have different requirements. Without documentation, you are 'playing in the dark'.

 

[smeezekitty]

What are the markings on the existing battery ?

Rayovac computer clock battery

Different motherboards have different requirements. Without documentation, you are 'playing in the dark'.

Thats what I was afraid of. I don't have any documentation, and if I do need to adjust jumpers, it will not be fun because I can see there are some under the hard drive cage.

 

[modem7]

Rayovac computer clock battery

That is on one side of the battery. Are there no marking on the other sides? There may be some under the vecro strip.

 

[modem7]

As I understand, I need to install RAM sticks in multiples of 4, correct?

A 486 based computer has a data bus that is 32 bits wide. So the answer depends on the RAM that the particular motherboard supports.
If the motherboard uses RAM sticks of 8-bit data width, then the RAM is fitted 4 sticks at a time (4 x 8 = 32).
But if the motherboard uses RAM sticks of 32-bit data width, then the RAM can be fitted one stick at a time.

Different motherboards have different requirements as to which RAM slots are used before others, the type of RAM, etc.

Some motherboard manuals will even indicate known compatible RAM, eg.
"The following make/model of RAM has been successfully tested on this motherboard:
AAAAAAAAAAA
BBBBBBBBBBB
CCCCCCCCCCC
DDDDDDDDDDD
The use of RAM other than that listed above may result in the motherboard not working, or result in unstable operation."

 

[smeezekitty]

Finally got to look at the battery. It is 4.5 volts alkaline!
I should be able to just solder 3xAA or 3xAAA holder to the connector then, correct?

Still concerned about the RAM

 

[Caluser2000]

Have you cleaned the simm slot contacts?

 

[modem7]

Finally got to look at the battery. It is 4.5 volts alkaline!
I should be able to just solder 3xAA or 3xAAA holder to the connector then, correct?

Yes, that is correct.

 

[smeezekitty]

Have you cleaned the simm slot contacts?

No. I am not having any problems.
I just don't want to buy RAM that turns out to not work with it or not be able to figure out how to configure it.

 

[Caluser2000]

Why not post a decent picture of the motherboard? Someone here is bound to be able to ID it and it'll take the guess work out of you're ram selection.

 

[Stone]

I'm going to make an educated guess and say that this board uses 1Mx9 and 4Mx9 SIMMs.

 

[smeezekitty]

I took some pictures but I cannot really get good pictures with all the stuff in there.
I guess I will probably have to bite the bullet and try to buy some RAM

 

[smeezekitty]

Here are some pictures of the CMOS battery mod

 

[smeezekitty]

I am having the worst luck right now! Besides the floppy drive problem, I install RAM and its not working right!

These are the RAM sticks: http://doc.chipfind.ru/samsung/kmm594000a8.htm
This motherboard is similar but not identical: http://stason.org/TULARC/pc/motherboards/C/COMPUADD-INC-486-486-ISA-HP-SX-DX.html

I installed 4 sticks in bank 3 and I got this:
Memory write/read failure at 00800000, read 806f806e expecting 806f806f
Decreasing available memory

The address sometimes changes but the failed bit is always the same
To make things worse, I cannot figure out how to remove the simms
So did I get one or more DOA sticks or am I doing something wrong or is the motherboard flaky?

 

[smeezekitty]

I finally figured out how to get the sticks out. You need to poke out the latch with something pointy and kind of work it out.
Annoyingly difficult and concerning.


In any case, I think I found trouble. One of the sticks had corrosion on some of the pins and one or two legs of one of the chips.
I managed to remove it from the contact pins but now it won't count past 8MB at all. I suspect that the corrosion is the cause and I should contact the seller.

 

[modem7]

The motherboard has 12 RAM slots, of which there is current 8x1 MB 30-pin parity RAM sticks installed

So, banks 0, 1 and 2 (3 banks of 4 slots).

I installed 4 sticks in bank 3

That must be bank 2, the third bank.

Bank 0: 4 x 1MB SIMM: 0MB to 4MB-1
Bank 1: 4 x 1MB SIMM: 4MB to 8MB-1
Bank 2: 4 x 4MB SIMM: 8MB to 24MB-1 <--- what you have added

Memory write/read failure at 00800000

Address 800000 hex = 8 MB
So, there's a problem in bank 2.

read 806f806e expecting 806f806f

A single bit in error. Try swapping the 4MB SIMS about within the bank and see if the bit-in-error moves accordingly.
And check the bank 2 sockets for dust/hair, a possible cause of a connection problem.

To make things worse, I cannot figure out how to remove the simms

Be careful. The thought of "perhaps it needs just a little more force" often results in breakage.

 

[smeezekitty]

^ forum bug - your post is after my response

-edit-
whoever designed these simm slots should be whipped


-edit again-

I swapped out the bank 1 chips with the new chips and it only show 4 MB - so I guess I have atleast 1 DOA stick. I almost broke one of the old sticks trying to get it out because of the terrible simm sockets.

 

[smeezekitty]

I found that two sticks had corrosion on them and RMA'd them.
The new sticks solved the problem and I am now showing 23 MB extended.

Thanks for trying to help though.