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Dell 433s/x build memory issue

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First post, by Arbuthnot

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Hello all, new here. I've acquired a Dell 486SX (433s/x) motherboard to rebuild my dead old PC from when I was a kid. I am struggling to find much information on it but it appears to be this board: https://web.archive.org/web/19970224223616/ht … 86L/default.htm It is working OK with the 4 old 4MB 72-pin chips from my dead IBM, but I was hoping to upgrade it to 64MB total so I picked up some 16MB SIMMS from eBay. The board will POST with any one of them and shows 16MB installed, but it won't take more than one. I realised that I had bought 60ns memory and the board details linked say 70ns - could that be why it will not take more than 16?

Reply 1 of 9, by Horun

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Hmmm are the old 4Mb SIMMS single sided: all chips on one side, typically 8 or 9 of them ?
Manual does say it supports up to 64Mb using 16Mb SIMMS. Being 60nS they should work because 60nS is capable of being faster than 70nS... unless your SIMMS are an odd chip layout. Can you post pictures of you SIMMS ? Most old 486 16Mb 72pin were single sided with 8 chips or 9 chip. If using some of the newer (Pentium compatible) 2 chip or 3 chip type they could be double density which means each actually uses same as two SIMM sockets for addressing. If that the case then best scenario is only two will work being spaced by one empty SIMM socket. Just guessing at this point but is a possibility....

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 2 of 9, by Arbuthnot

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Thanks for the reply. 3 of the 4MB chips are single-sided with 8 chips, one is double with 12 chips (makes unknown).
The 16s are single-sided, Texas Instruments TM497FBK32S-60 72-Pin 60n/s EDO. 8 chips per stick.

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Reply 4 of 9, by Arbuthnot

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Hello, the 4MB chips that I have that work are 1 x double side and 3 x single side. Here are pictures of the double and one of the singles. Thanks.

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Reply 5 of 9, by pentiumspeed

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Yes, I ask photos of both sides of the double sided memory to see what other side looks like.

By the way, Dell of this type typically requires parity memory. Just like Compaq Deskpros and PS/2 were all parity memory required.

Cheers,

Great Northern aka Canada.

Reply 6 of 9, by Arbuthnot

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The 2 photos in my previous post do show both sides of the double-sided memory chip I have - it's the one with the gold contacts. RE: parity memory, the guidance I found for the motherboard (linked in my first post above) says non-parity?

Reply 7 of 9, by pentiumspeed

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The gold one is parity memory. Was this original with Dell 486 based? That's your answer! FPM, parity or non parity DIMM is required for this computer.

Oh, EDO will not work in your computer, you should had stated that early on, EDO is for Pentium boards. Next time buy FPM parity or non-parity 16MB DIMMs, 70ns or 60ns.

Sorry, Cheers,

Great Northern aka Canada.

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