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The Digital DECpc 425sx/LP

k2x4b524[

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Got one of these little beasties from a recycler who was gonna chuck it.

It's a 486SX-25 Machine, made by Digital.

What makes it special, is the fact that is can, STABILY, support 50mhz bus, Hence i gave it my 486DX-50.
It is purely isa, no vlb or pci, but i think the onboard may be VLB, but it's got no problems, i THINK it might be able to handle a DX4-100 or a DX2-100 if there is such a chip as a DX2-100. I believe it can support up to 64mb ram onboard aswell.

I am unable to locate a user manual through google, and will post a pic or 2 once i finish upgrading it
 

vwestlife

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What makes it special, is the fact that is can, STABILY, support 50mhz bus, Hence i gave it my 486DX-50.
It is purely isa, no vlb or pci, but i think the onboard may be VLB, but it's got no problems, i THINK it might be able to handle a DX4-100 or a DX2-100 if there is such a chip as a DX2-100. I believe it can support up to 64mb ram onboard aswell.

Any Intel 486DX4-100 should be able to run in 50 MHz x 2 mode as well as 33 x 3. It is an officially supported, but rarely documented feature of the chip. I'm not so sure about the AMD or Cyrix versions, however.
 

k2x4b524[

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well, the thing is the board doesn't let you set the multiplier, just the bus speed, so that 100 would be trying to pump away at 150 and a 120 would be trying to go around 200mhx, the 486-dx2-80 would be a better best being 40x2 so 50x2 would give 100 and with proper heatsink, still be stable, but the socket 3 on the board is a 5 volt, not 3 or 3.3, and i'm not sure if my one and only interposer works or not
 

Tetrium

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Iirc not all Intel DX4's supported the x2 multi. Even if they do, likely his board doesn't support 3.3V CPU's. Ofcourse theres adapters for the voltage thingy

I'm not sure what the default multi would be on an Intel DX4. If it defaults to x2 and you got the voltage regulator then perhaps it'll work

Edit:Found a helpfull page about DX4 multipliers
http://en.wikipedia.org/wiki/Intel_80486DX4
 

k2x4b524[

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I'm pretty sure it won't load up, i have the voltage regulator from a Kingston 486/TC100 Step-up chip, and all my higher end chips refuse to work. BUT the board's jumpers SAY to use a certain setting for DX OR DX2 so i'm thinking that it MAY support both voltages despite being an older style socket. However without the regulator thingy, everything up to my DX-50 works, hell my socketable 486SX-33 works in it also, it's just everything with a DX2 or greater multiplier, and the voltage thingy, refuse to work, that includes my 5x86 ADW, my 5x86 ADZ, and my IBM/Cyrix 5x86-133, they all get warm, meaning they are getting power, just nothing is happening
 

Raven

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DX2-100 does exist, but they're a rare upgrade to the rare DX-50 systems.

The 5x86ADW chips are pretty happy with almost any signals fed into them - try them on DX and DX2 settings, either will work, worst case is an underclock.

I've run them successfully with every jumper combo available in my ValuePoint, none of which raising the speed or lowering it, however. ValuePoint refuses to run above 101mhz. The two jumpers it has are DX/DX2, and OD/DX(2?)..
 

k2x4b524[

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Update: I'm leaving it with my DX-50 as it seems the most stable of the chips the MB will take. BUT i can't find a user manual for it ANYWHERE, i would like to bring the ram up to 32mb or 64mb, but it appears to only see 16mb simms max. Also, in the 4th simm slot, whatever simm i put in it it won't recognize ANY extended memory. Is this thing just really anal about memory or am i doing something wrong with it?
 
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