Using a Dell 486P with non-parity RAM

Discussion about old PC hardware.

Using a Dell 486P with non-parity RAM

Postby mdog69 » 2019-11-15 @ 18:44

I have a Dell 486/P.
The motherboard matches that shown at https://stason.org/TULARC/pc/motherboar ... -486P.html
and the links are more accurately described here: http://ps-2.kev009.com/ohlandl/PS2_MOST ... 006005.PDF

The board has 4x 72pin SIMM slots, which will accept 1, 4 or 16Mb with parity.
The problem is that I only have 4Mb and 8Mb parity SIMMs. The 8Mb SIMMs get recognised as 4Mb, so I'm stuck with 16Mb.
I do have some 16k FPM non-parity SIMMs, but these are either ignored, or give a memory error.

The BIOS setup is a two page "dumbed down" menu with no way of disabling RAM parity.
The Phoenix motherboard BIOS is version "1.10 A09", and lives on a soldered in 28F001 flash device (rather than in a EPROM socket which would make life easier).
The setup menu is a two page "dumbed down" menu with no option to disable RAM parity.
It also has an XTIDE ROM installed in a 3C509 card to get around the 504/528Mb disk limit.

The only other information I have is as follows:
1) JP5 has the following functions (not as documented via the link above)
Code: Select all
                                        Closed  Open
VIRQ            VGA Interrupt           None    IRQ9*
RSET            Reset for factory diag  On      Off *
MOCO            Mono/Colour             Colour* Mono
MNT             Resrved manuf maint   On      Off*
EPWD            Password on/off         On*     Off
MIRQ            Mouse enable/IRQ        IRQ12*  Off
NIDE            New/old IDE drive       New*    Old
OIDE            New/old IDE drive       Old     New*
NWAT            Normal ISA cycles       Normal* 1xWait State
ATRM            ISA Exp bus boot        Enable  Disable*
             * = current setting


Does anyone know if this board can be knobbled into accepting non-parity RAM, either by some undocumented hardware hack, updating the motherboard BIOS, or at a pinch, shoehorning a kludge into my XTIDE EPROM?

/mdog69
mdog69
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