Using SDRAM in Mainboard New Generation VXpro+ Chipset

Posted on 1998-09-02
Last Modified: 2013-11-10
Can only get SDRAM to read at 1/4 of total in this board.  Example-128 meg reads 32, 64 reads 16.  with both installed, they read 48 at boot up.  Simms chips read ok and EDO reads ok. Currently have 128 & 64 SDRAM and 2-16 SIMMS installed.  Reads 81 at boot up.  What do I need top do so it will read all of memory?
Question by:terryj
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Expert Comment

ID: 1124314
Are you sure they're 128 and 64?
128MB SDRAMS should have '16-64' somewhere on a label or the sales invoice (16-72 if with parity),64MBs are 8-64.
I assume you've already tried each alone - with all other memory removed.
Are both from the same manufacturer?
What CPU and what speed are the SDRAMS - 66 or 100MHZ?
Do you get the same results in another 168 pin socket?


Expert Comment

ID: 1124315
Try another manufacture of SDRAM.  I had the same problem with a chip.  It wouldn't read correctly in three workstations it was made by a top named manufacture.  Replaced it with a cheeper smaller warentee and it shows the correct memory.

Expert Comment

ID: 1124316
what type of mainboard do you have? Do you have jumpers for your
d\simm voltage?Is you bios set right ?Does your mainboard manual
say it can handle the ns(nano seconds)usally 80-10 of the
d\simms?Plus MATTCEI asked my first? PLEASE answer it might help!
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Expert Comment

ID: 1124317
I agree with checking the Ram and making sure it is the size you think it is. Second i would take out the simms and try only the SD-Ram in the board. THis may help.
LVL 32

Expert Comment

ID: 1124318
If you know that the SDRAM is good (or if more than one module is doing this), you have a defective motherboard.  Most likely is a dead address line on the memory bus.

Expert Comment

ID: 1124319
Try to disconnect EDO ram.
Connect your SDRAM.
Boot, and look Memory size.

-Sometimes there is a relation betwen EDO Ram size and SDRAM size.  
-Sometimes if you have 2 banks for EDO and two banks for Dimms you can't use in the same time EDO and DIMMS banks.
With my motherboard, if i use EDO banks, only 1 SDRAM bank is available.


Expert Comment

ID: 1124320
You have the same motherboard in my kids comp.Notice Dimm2
and simm1,2 can not be installed at the same time!

Author Comment

ID: 1124321
Chips are good and are correct size.  Tried on another board and they worked ok.  However, I have a friend who has the same problem with different chips. The catalogue that came with the board shows it to be "MAINBOARD" Pentium MMX New Generation VXpro+ Chipset.  
LVL 32

Expert Comment

ID: 1124322
If you know that the SDRAM is good (or if more than one module is doing this), you have a defective motherboard.  Most likely is a dead address line on the memory bus.

LVL 12

Expert Comment

ID: 1124323
Read the manual. VXPro chipset does not allow many dimm and simm combinations.

Accepted Solution

second earned 100 total points
ID: 1124324
Try the same DIMMS (128 & 64) in another board and
try other DIMMS (128 & 64) in this (VXPro+) board.

I think I understand what is going on:
The 128MB DIMM is maked from 16chips x 8MB each (16x8=128MB), but your board/chipset don't support 8MB chips, it should support only 2MB chips. So when the board recognises the DIM Module correctly as 16chip module it calculates 16x2MB=32MB and allocate only 32MB of the 128MB-DIMM. The same with 64MB (you must have "small" 64MB DIMM - with 8 chips - the  "big" is with 32chips and is double-high) The board recognise it correct as 8chip and calculate 8x2MB=16MB...........
So try one 64MB DIMM with 32chips (double-high Module), but it is possible that your board don't support 32chip-DIMMs. So better try one 32MB DIMM with 16chips (2MB each) and see what happen..........

P.S. The "Pro" boards aren't very good . Your VXPro+ is not an excluson. Better buy a MVP3, MVP4, Alladin V board................

Expert Comment

ID: 1124325
I have sended a answer, but something more:

DIMMs with 2MB chips:
8chip - 16MB
16chip - 32MB
32chip - 64MB (double-high Modle - like two modules placed ine over the another; not all boards/chipsets, especialy the olders, not all boards support 32chip modules)

DIMMs with 8MB chips:
8chip - 64MB
16chip - 128MB
32chip - 256MB (not-yet-released, but soon)

Be sure the ns (in BIOS) are set properly;
It is not very good to mish SIMM/EDO & DIMM/SDRAM even if the board support this - the voltage is different, speed too, etc.
It is best to use two(2x64MB are faster than 1x128MB) fully identical SDRAM DIMMs with 8chips and 7ns

Expert Comment

ID: 1124326
happy to help

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