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dongfeng
August 13th, 2006, 11:25 AM
My 486DX33 currently has four 1MB 30-pin SIMMS in bank 1, giving a total of 4MB memory. I would like to put some additional memory in bank 2, to make the computer a bit more useable! According to the motherboard listing, I can make a total of 20MB by keeping the 4 x 1MB SIMMS in bank 1 and putting 4 x 4MB SIMMS in bank 2.

It's been a LONG time since I dealt with 30-pin SIMMS, how can I tell which memory I require? I seem to remember them being quite fussy.

Regards,

Jorg
August 13th, 2006, 11:49 AM
The question is if the motherboard supports that config- only the manual can tell you.
On 30 pin simms the number of chips might play a role in that, 9 vs 3 iirc.

4 MB 30 pin simms are very hard to find I believe.

dongfeng
August 13th, 2006, 11:54 AM
The manual tells me:


20MB
----
Bank 0: (4) 1M x 9
Bank 1: (4) 4M x 9


When I look at the SIMM itself, there are 3 chips on it and the pins are gold.

Jorg
August 13th, 2006, 11:57 AM
The manual tells me:


20MB
----
Bank 0: (4) 1M x 9
Bank 1: (4) 4M x 9


When I look at the SIMM itself, there are 3 chips on it and the pins are gold.

That looks good, I remember the 9 pin chips gave trouble sometimes

dongfeng
August 13th, 2006, 12:26 PM
then what is the meaning of the x9 in the manual?

mbbrutman
August 13th, 2006, 12:29 PM
30 pin SIMMs are either parity or non-parity. Non parity SIMMs will generally be constructed of 2 chips (4 bits wide) or 8 chips (1 bit wide), for a total of 8 bits. Parity SIMMs will be generally 3 chips (2x4 + 1x1) or 9 chips for a total of 9 bits.

Parity SIMMs are preferred, but sometimes the number of chips causes electrical loading problems.

In ye olden days, it was a common cheat to have 'parity SIMMs' that faked the 9th bit. Instead of having a true parity bit, a cheap chip would just compute the correct parity value. For boards that required parity it would work, but the answer would always be 'correct' because of the fakery, so it was worthless.

Look for 60ns SIMMs on a 486 at high clock speeds. 70s were also common, and can be accomodated by tweaking the BIOS settings a little. Above 70ns forget it .. not unless the bus speed on your machine was very slow. (The motherboard manual will specify the speed to use.)

And look for a 'matched set' of 4 to avoid flakiness. In theory a mixed set is fine, but matched works better in practice.

mbbrutman
August 13th, 2006, 12:29 PM
BTW, this belongs in Hardware.

dongfeng
August 13th, 2006, 12:48 PM
That's great, thanks for explaining! It seems, since my current SIMMS have 3-chips, I will need some parity SIMMS to add.

I have another question though. There are 4 1MB 30-pin SIMMS in my 286, and they have 9 chips on them. I removed the original memory from bank 0 on the 486, and put in these new ones. It worked fine. However, when I add both sets (so banks 0 and 1 are full of 8 1MB SIMMS making a total of 8MB) the computer will not boot.

mbbrutman
August 13th, 2006, 01:45 PM
Read the numbers on all three chips to be sure that it really is a parity SIMM. Memory chips can be identified by number. The fake parity generators will show up as something other than a DRAM.

The DRAM chips will have part numbers on them and usually a speed rating. The speed rating will usually be after the part number and will have a '-' followed by a number, such as 60, 70, 80, 12. Chances are that the SIMMs in your 286 are *far* slower than the SIMMs in your 486, and that might be causing the problem. Also, the motherboard may have restrictions on the allowable speeds that can be mixed.

Amiga4k
August 17th, 2006, 10:53 AM
Dongfeng,
I have boxes of 30 pin simms, all sorted. Whatever flavor you need with 256k, 1 meg, 4 meg in either 3 or 9 chip.
What speed are your present 30 pin simms?

PS> as I only have 2 of the 9 chip and 4 of the 3 chip, you will have the right of first refusal.

Best to email me, as I visit so seldom.

Sharkonwheels
September 25th, 2006, 01:18 PM
Dongfeng:

a little late, but see if the manual says it supports 16MB 30-pin simms.
I have about 40 of them, matching brand. Samsung I believe.


Tony

lonnieredskinds
September 28th, 2006, 10:00 AM
[QUOTE=dongfeng;26290]My 486DX33 currently has four 1MB 30-pin SIMMS in bank 1, giving a total of 4MB memory. I would like to put some additional memory in bank 2, to make the computer a bit more useable! According to the motherboard listing, I can make a total of 20MB by keeping the 4 x 1MB SIMMS in bank 1 and putting 4 x 4MB SIMMS in bank 2.

It's been a LONG time since I dealt with 30-pin SIMMS, how can I tell which memory I require? I seem to remember them being quite fussy.

i have around 30 or so 30-pin simms will let you have them for $ 10.00 s/h
also have a card that holds 4 30 - sims just plug it in tis got 4 simms in it
that i will let you have for $ 5.00 i la so have a post that im givining away
old disk drives modems motherbords ribbions some other stuff im moving
cant take it with me if you want to see any pic of what i have them email
me lonnieredskinds@yahoo.com

lonnieredskinds
October 4th, 2006, 12:53 PM
have a lot of it 30 pin sims cheep moving cant take with me have a lot of
free stuff hard drives mother boards modem a-drive all kind cards if anyone wants to see pic they can email me i will send you pic all you do is pay s/h it free lonnieredskinds@yahoo.com

Mike Chambers
October 6th, 2006, 08:48 PM
my 386 DX/40 and 386 SX/20 both take these types of chips... if i had more i would send them do you just for shipping costs. sorry. i had purchased two SIMMs (a 1 MB and a 4 MB from memoryx.com) CHEAP

i didnt find out until i received them, that i needed at least four chips to make it work. :/

luckily i went through all my boxes of old computer stuff in my basement and found two extra chips. stuck them on the DX/40 board and it turned right on. however, it only reads 3.7 MB total even though two of the chips are 4 MB(for a grand total of 6) oh well. at least it works.

check this link out, this is where i got my chips:
http://www.memoryx.net/generic-memory-30-pin-simm.html