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Floppies_only
June 5th, 2010, 08:16 PM
Gang,

If anybody is interested, there is a _possibly_ good deal on an IBM PC/AT model 5170 on ebay right now (I don't know the seller). It has a memory expansion card that I'm guesstimating has 12 megabytes of memory on board, if the chips are 128k by 1 bit chips. I hadn't thought they made them in that size but I also thought the AT had a memory size limit of 16 megabytes, so it seems not to meke sense to have a memory card for an AT with 24 megs on it. It's being offered on ebay for a buy it now price of 69.99, and shipping for me would have been about fifty dollars more.

The battery is present and it appears that it hasn't leaked. I looked in my Technical Reference and it said the battery connector was a "4-pin, keyed, Berg strip". Pin 1 is ground, pin 4 is for +6 volts DC. I didn't look online to see how to tell which pin is which, but it might be possible to find out from one of the major parts houses or figure it out from the existing battery (the red wire is positive).

The computer looks nice for a used AT but the catch is that the seller doesn't have a monitor. He can't park the hard drive heads and the Guide To Operations manual says that data can be lost from the hard drive when moving the unit (apparantly even when you do park the heads). The problem this poses is that the driver for the RAM card (an AST model but I couldn't find the drivers for anything other than the sixpak) could have been damaged or could be damaged in shipment, making the computer a fancy 512K model with extra power draw.

If anybody has the drivers, knows how to get them, or is willing to gamble, here is the link to the auction page on ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110542311191

Oh, the computer also has two serial/parallel cards, what appears to be a network card, and another card with a nine pin female d-shell connector, like an MDA card but half-length instead.

Sean

Floppies_only
June 5th, 2010, 08:23 PM
...the Guide To Operations manual says that data can be lost from the hard drive when moving the unit (apparantly even when you do park the heads).

Oh, I figured it out. This can still happen, but the UPS guy has to throw the package on the ground harder :)

Sean

modem7
June 6th, 2010, 02:28 AM
The battery is present and it appears that it hasn't leaked. I looked in my Technical Reference and it said the battery connector was a "4-pin, keyed, Berg strip". Pin 1 is ground, pin 4 is for +6 volts DC. I didn't look online to see how to tell which pin is which, but it might be possible to find out from one of the major parts houses or figure it out from the existing battery (the red wire is positive).
I have added a 'battery' section to the IBM 5170 page at our wiki - http://wiki.vintage-computer.com/index.php/IBM_PC_AT_%285170%29


The problem this poses is that the driver for the RAM card (an AST model but I couldn't find the drivers for anything other than the sixpak) could have been damaged or could be damaged in shipment, making the computer a fancy 512K model with extra power draw.
The eBay photo shows that only 256K is fitted on the motherboard.

Note that there appear to be 2 RAM cards. The one known to be an AST is in slot 5. It has 16 switches at the top. The adjacent card, in slot 6, is the one with the daughter board bolted on.

Floppies_only
June 6th, 2010, 02:44 AM
The eBay photo shows that only 256K is fitted on the motherboard.

Note that there appear to be 2 RAM cards. The one known to be an AST is in slot 5. It has 16 switches at the top. The adjacent card, in slot 6, is the one with the daughter board bolted on.

You appear to have eagle eyes. I looked at those pictures for a long time.

I thought later ATs came with bigger chips on the motherboard so that they didn't have to double stack them to get 512k. Is it possible to use expanded memory in an AT which doesn't have the maximum amount on the mother board? How much memory would you estimate this one has?

Sean

modem7
June 6th, 2010, 04:28 AM
I thought later ATs came with bigger chips on the motherboard so that they didn't have to double stack them to get 512k.
The chip layout in photo #12 (the last one) proves that the motherboard is the original IBM type 1. So this is an early AT, one with piggyback (double stack) RAM chips on the motherboard. Photo #11 shows only the first 256KB bank populated (2 rows, of which 1 row can only just be seen).


Is it possible to use expanded memory in an AT which doesn't have the maximum amount on the mother board?
Yes, although increasing the base memory to 512K (or 640K) would be a good first step.


How much memory would you estimate this one has?
I'm not willing to estimate.
I will guess that the AST card in slot 5 is probably topping up the base memory from 256K to 512K (or to 640K), and that the card in slot 6 is providing a certain amount of extended memory.