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Pre-Post analysis.

Micom 2000

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Back in the 80s and 90s there were these marvelous testers which would test the functioning before the BIOS Post kicked in. Every computer repairman would love to acquire one, but they were quite expensive. I could never afford one, but acquired a cheap chinese one some time back which supposedly did the same thing. Has anyone here used them ? Either the original machine or the chinese version. I wonder if it could be used to check whether or not a processor and motherboard was working.
 

sergey

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Are you're talking about a POST card?
These cards doesn't really test anything before BIOS POST, they just display POST codes that BIOS outputs.
I personally doubt usefulness of such cards for computer repair. They might diagnose issues and help with repairing older boards built from 82xx ICs (mostly early 80286/80386 motherboards). But even in this case they only work if the processor is able to fetch and execute instructions from the BIOS, which assumes that all the bus logic is working. On newer motherboards they not really useful - most likely you're not going to replace a chipset...

I personally not sure why these boards were expensive, it takes only a few very common 74xx ICs and a seven segment LED indicator to build one.
 

Micom 2000

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I do mean the Post card. This was in the era you mention, 80s early 90s. To my knowledge you could use it to test a motherboard without a drive or monitor installed. As I say, I never did use it. Oh well. :^(

L.
 

sergey

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I do mean the Post card. To my knowledge you could use it to test a motherboard without a drive or monitor installed.

Yes, you can use it to test a motherboard without disk drives or video card. At least to the point where it tries to boot.
Some of more advanced cards offered additional activity indicators. Such as LEDs showing CPU clock or activity of CPU control signals.

My ISA Backplane, which has a built-in POST indicator, uses decimal point segments to show activity on A8 address line. It is a very basic indicator of the CPU activity. If CPU is working and fetching instructions or data (even if there is no BIOS), these segments will flash.

Edit: You can refer to the schematics to understand the complexity of POST indicator... It is only 5 74LS* ICs (6 with 74LS74 for the A8 activity) and 2 position 7 segment LED indicator. Although many commercial boards reduced component count even more (to 3 ICs or even one) by using PAL/SPLD/CPLD programmable logic instead of generic logic.
 
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