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View Full Version : Olivetti m24 ram fail



simon_the_s
February 17th, 2016, 12:28 AM
Hi

Referering to this old thread http://www.vcfed.org/forum/showthread.php?31130-olivetti-m24-ram-fail/page2&highlight=olivetti+m24

My problem summarized:
Ive got an old Olivetti M24 - which powered up after several years of neglect, fails to detect the 640kb ram it should. it just stalls at 128kb:

29616

So ive tried taking out all the socketed ram in bank1:

29617

- and starting up the machine - same issue - though i later found out (through help of this forum) that this not possible without altering dipswitch0 setting:

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according to http://compgeke.com/files/PC6300/PC6300ServiceManual.pdf page 92 and on.

However i cannot in this manual find the settings for the 128kb settings.

So i have three questions:

1: Does anyone know the dipswitch0 settings for 128kb ram.

2: Can i start up the system with this 128kb settings without removing the socketed ram - or would this cause an error.

3: In the old thread i was suggested to piggyback the socketed ram to identify the faulty one(s). I am still not sure how to practice this - how to tell if the ram is faulty.

Any help is greatly appreciated.

-Simon

pietja
February 17th, 2016, 01:10 PM
On page 574 of the pdf document are the settings for 128kB
maybe playing around with the different 640kB settings will do something ?

1ST1
February 17th, 2016, 10:43 PM
Here you have a more detailed thing, I think it should help to locate the faulty ram: http://bitsavers.informatik.uni-stuttgart.de/pdf/olivetti/m21_m24/Olivetti_M21_M24_Theory_of_Operation_Nov84.pdf

simon_the_s
February 17th, 2016, 11:32 PM
On page 574 of the pdf document are the settings for 128kB
maybe playing around with the different 640kB settings will do something ?

Thanks - had not seen that - do you know if i have to remove the socketed ram when running the system at 128kb configuration?

Last time i took them out i bent some legs - and i would like to harm them as little as possible.

-simon

simon_the_s
February 17th, 2016, 11:53 PM
Here you have a more detailed thing, I think it should help to locate the faulty ram: http://bitsavers.informatik.uni-stuttgart.de/pdf/olivetti/m21_m24/Olivetti_M21_M24_Theory_of_Operation_Nov84.pdf

Thanks for link.

On page 73 i find the following:

29642

Now since i dont have a memory expansion board - and - it used count 640kb ram - i can coclude that i should have 512kb in BANK0.

Since it only counts 128kb now - the faulty ram is one of the soldered ram chips? - is that a valid conclusion?

btw if any1 can tell me anything from the part numbers on the picture of the ram banks it would be great - cant seem to find anything useful.

-simon

pietja
February 18th, 2016, 12:49 AM
You have 128kB of soldered MCM6665BP15 ram in BANK0 and 512kB of socketed MT1257-15 ram in BANK1.
If you remove all the ram in BANK1 and adjust the dipswitch for 128kB then you know if the soldered ram is good.

Check if all the pins of BANK1 are actually inside the socket pins, because you have bent pins and they could end up under the chip instead of in the socket.
So make sure all the pins are straight and put them back in carefully, if you happen to brake a pin of you can still find some new ram online. (http://www.ebay.com/itm/221482382200)

simon_the_s
February 18th, 2016, 01:03 AM
You have 128kB of soldered MCM6665BP15 ram in BANK0 and 512kB of socketed MT1257-15 ram in BANK1.
If you remove all the ram in BANK1 and adjust the dipswitch for 128kB then you know if the soldered ram is good.

Check if all the pins of BANK1 are actually inside the socket pins, because you have bent pins and they could end up under the chip instead of in the socket.
So make sure all the pins are straight and put them back in carefully, if you happen to brake a pin of you can still find some new ram online. (http://www.ebay.com/itm/221482382200)

ok thanks for the clarification - it was just since there was no configuration in:

29643

for 512kb in bank1 i thought it was the other way around.

anywas i will try what u have suggested when i get home - thanks

pietja
February 18th, 2016, 01:33 AM
That table is for the 1.21 BIOS, you have 1.43 so use the table on page 574 of the first pdf. (http://compgeke.com/files/PC6300/PC6300ServiceManual.pdf)

simon_the_s
February 18th, 2016, 08:16 AM
so i removed all the socketed ram.
set dipswitch0 to 01111111. (which i think should be the correct setting for 128kb?)

now when i boot - it gives a short beep - and the lights in the keyboard go out - nothing on the screen.

pietja
February 18th, 2016, 01:52 PM
The dipswith is right (all down except the first)

Strange that wont boot because at first it stops at 128kB and now that you have exactly that 128kB and wont boot at all.
Does it hang at the 128kB if you set the dipswitch back?

Have you found any really bend pins on the socketed ram?

simon_the_s
February 18th, 2016, 10:17 PM
Ill try set the dipswitch back and boot up again.

There didnt seem to be any pins on the ram blocks that was very bend - i took my time removing them.

Trixter
November 4th, 2016, 08:40 AM
To the original poster: Did you ever find the fault and repair your M24?