Genuine IBM 5170 AT mobo with generic case needs TLC

[rmay635703]

My old IBM 5170 has sat missing 1 piggyback chip for a long time and has 2 others dislodged.

I am curious if I can substitute Siemens 41256-12's in my old AT mobo.

I am uncertain if the pinouts are the same as the old TI ZA1250Nls aren't spec'd anywhere.

I have a feeling that if the address pins, voltage and ground end up where they are supposed to be the board should use the chips but won't see them at full capacity, probably half.

Any ideas?

Also on an off topic this board appears to have 2 standard BIOS chips and one of the old window type chips, IS the AT board one of those that would tolerate a bios from a more modern AT board?

I have a 1989 AMI 286 bios plus in the old ODD EVEN 2 chip format that looks like it would fit right in, unless those are for basica.

I really don't know much about the true blue AT, like I do for the PC/XT's

Thanx
Ryan

http://www.vintage-computer.com/vcforum/newthread.php?do=newthread&f=22

 

[glitch]

I do have some of the double-stacked DRAMs, pulled from a mouse-crap-corroded 5170 motherboard, if you need them.

 

[modem7]

There's a lot of technical info on the 5170 at these forum's Wiki (the VCWiki): http://wiki.vintage-computer.com/index.php/IBM_PC_AT_(5170)

That document includes known replacements for the ZA1250NL.

The pinout of the ZA1250NL can be found in the schematic diagram of the early 5170 motherboard (type 1 motherboard).
That diagram can be found at http://members.dodo.com.au/~slappanel555/misc/schematic_5170_motherboard_type_1.pdf
The 36 ZA1250NLs are shown on sheets 8 and 9.

 

[rmay635703]

Hmm, I wonder what pin 8 does? Everything else is listed, now to find the pinout of 41256's (siemens)

If everything matches worth a go, only trouble is I don't have enough of the to fill both banks only 0 or 1 which could result in strangeness if the mobo interlaces the ram as I believe is alluded.

Thanx
Ryan

 

[mikey99]

Are those just double stacked 64k chips ? If so could you just stack two 64 K chips and lightly
solder each lead ?

 

[modem7]

Hmm, I wonder what pin 8 does?

Pin 8 is the VCC pin. Pin 16 is GND.

only trouble is I don't have enough of the to fill both banks only 0 or 1 which could result in strangeness if the mobo interlaces the ram as I believe is alluded.

Per the VCWiki article, population of only bank 0 is a valid option. Set the RAM jumper accordingly.

Are those just double stacked 64k chips ?

No. The two chips differ slightly.

 

[rmay635703]

Pin 8 is the VCC pin. Pin 16 is GND.

It appears the DI, WI & RAS all need to move Also RAS0 & RAS1 would need to be tied together

Per the VCWiki article, population of only bank 0 is a valid option. Set the RAM jumper accordingly.

But I want to have the full 512k and use both banks, I have one bank (complete of 128's) and would like to use a set of 256's as 128's for the other bank

No. The two chips differ slightly.

You could do that but the pins need to move to different locations which would be both cobbbled up and very challenging to make. AKA the RAS from one chip goes next to the RAS of another so there are two ras lines to address both chips