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No RAM past 64K on 5150, 64K-256K MB, fully popped mem, 1501476 10/27/82 BIOS

K

KLund1

Veteran Member
Joined
Jun 22, 2012
Messages
561
Location
Livermore, CA
Hi everyone, Thanks for all past help for this IBM nube.
I'm not getting any ram past 64K after a cold boot. I get no errors, no 201's, nothing. I only have a monochrome video card installed, no FDD. After boot, long pause with flashing cursor, then Basic comes up, it shows 62940 bytes free (= about 64K ??). The MB has all banks populated with the same numbered IC's. (TMS4164-20NL, AP8414)
Switch 1
1 on
2 off
3 off
4 off
5 off
6 off
7 off
8 on

switch 2
1 on
2 off
3 off
4 on
5 on
6,7,8 off

Jumper P4 is shorted M-C

Socket C28 is empty

Is my system running properly, or should there be something near 256000 bytes free??

Thanks
 
The 5150's cassette BASIC uses 64 KB of whatever RAM you have.
"It shows 62940 bytes free" is BASIC informing you of the amount of that 64 KB that is left for you to use in BASIC.
 
Following on from my previous email.
If you want to know much conventional RAM your 5150 motherboard is recognising, then type the following two lines into BASIC:

def seg = &h40
print peek(20)*256 + peek(19)

The figure that BASIC will show is in KB.

Based on your motherboard's configuration, you will be expecting to see "640" displayed.

But I have just now reviewed your switch settings, and the SW2 switches are incorrectly set. For a total of 640K, they need to be set per:
SW2-1: on
SW2-2: off
SW2-3: on
SW2-4: on
SW2-5: off
 
Unless he has a 384KB RAM card installed, he'd probably want it configured for 256KB - which I think it might be set to.
 
modem7 said:
The 5150's cassette BASIC uses 64 KB of whatever RAM you have.
"It shows 62940 bytes free" is BASIC informing you of the amount of that 64 KB that is left for you to use in BASIC.
Click to expand...
In case the thread starter needs some more info on that: the BASIC can only use a single segment of memory. A segment has 64 KB, so that's were the limit is coming from.
 
Thanks everyone,
So from all this I think my machine is working correctly.
Now to add and test this card http://www.vintage-computer.com/vcforum/showthread.php?46643-1982-STD-Memory-Expansion-IO-Card-ISA-8-Bit-IBM-PC-AT-XT-on-ebay

If this card does have extra usable memory, how much would this card add?
Then what would be the new switch settings on the MB so that the computer would recognize and do mem test on boot? I do understand that the switch settings on the card itself would have to set right. I am assuming they are, since this machine was fully functional in the long ago past.
Thanks again
 
KLund1 said:
Thanks everyone,
So from all this I think my machine is working correctly.
Now to add and test this card http://www.vintage-computer.com/vcforum/showthread.php?46643-1982-STD-Memory-Expansion-IO-Card-ISA-8-Bit-IBM-PC-AT-XT-on-ebay

If this card does have extra usable memory, how much would this card add?
Then what would be the new switch settings on the MB so that the computer would recognize and do mem test on boot? I do understand that the switch settings on the card itself would have to set right. I am assuming they are, since this machine was fully functional in the long ago past.
Thanks again
Click to expand...

Based on these assumptions:

- SW2 on 5150 set correctly (512KB setting)
- Memory card configured for a start point of 256KB
- Memory card uses 4164 (or equivalent) memory chips

It'd add 256KB of memory, giving you a total of 512KB.
 
I ran that little program and got back 256K. Thanks
When I install this card, I get a 5005 201 error. When I run that little program I get 640k.
SW2
1 on
2 off
3 on
4 on
5 off
6 off
7 off
8 on

SANY2964.jpg
Which IC do you think might be to offending critter? All the IC's look like 64 1bit, from 3 manufactures.
The board labels the sockets, looking at this picture, lower right as U28 up to C37, then U38 at the bottom of the next left column.
 
Last edited:
The card in the link earlier only had 256KB fitted, but yours has all six banks populated giving - 384KB (total of 640).

For the error code, I'd be looking at bit 0 and bit 3 in the second bank of memory on the ISA card but which ICs those are on your card I'm not sure.
Often they just need to be pushed in a little/reseated.
 
Hi, Thanks,
I reseated the whole row, same error. I'm not that familiar with these computer's conventions.
Second row in from the right
Starting at the bottom,
IC#2 bad?
IC#5 bad?
 
*** duplicate post***
Thanks,
I reseated all row 2, same error code.
I'm not that familiar with the conventions for this type of computer.
Starting at second row from the right.
starting at the bottom
IC#2 bad?
IC#5 bad?
 
KLund1 said:
When I install this card, I get a 5005 201 error. When I run that little program I get 640k.
Click to expand...
That is good. You are now only two chips away from a working set of 640K RAM.

SpidersWeb said:
For the error code, I'd be looking at bit 0 and bit 3 in the second bank of memory on the ISA card
Click to expand...
I'd be looking at bit 0 and bit 2.

KLund1 said:
Which IC do you think might be to offending critter? All the IC's look like 64 1bit, from 3 manufactures.
The board labels the sockets, looking at this picture, lower right as U28 up to C37, then U38 at the bottom of the next left column.
Click to expand...
The U numbers do not help us (unless a circuit diagram is found).

There is no single standard for how makers low out the RAM chips. The card's documentation, if it can be found, would show your card's layout.

On your card, the six columns will be the six banks of 64 KB, but is bank 0 on the far left, or on the far right! Some engineer who was designing the card may have tossed a coin to decide.
And is the parity chip at the top, or on the bottom!
You see where I am going.

Based on what I have seen on other cards, the eight most likely RAM layout scenarios are shown [here]. For each scenario, I have highlighted the two faulty chips.

What I suggest you do to identify the two faulty chips: In turn, with a power off/on in between, swap one of the red chips with its neighbour in an adjacent bank. If the '5005' in the 201 error changes, then you have identified a faulty chip (or rectified a poor connection).
 
modem7 said:
That is good. You are now only two chips away from a working set of 640K RAM.
Click to expand...
I have been lying again. After the chip problem in the card's bank 1 has been fixed, a reboot then may reveal a 201 error for bank 2, or bank 3, ...

modem7 said:
... swap one of the red chips with its neighbour in an adjacent bank.
Click to expand...
Because we know that bank 0 on the card is good (the RAM test passed through that bank), make the "adjacent bank" the bank 0 one rather than the bank 2 one.
 
I got this fixed finally. A it turns out this no name board has the same Mem layout as a AST SIXPACPLUS mem expansion board. I've also installed the RTC battery.
Thanks everyone for all your extensive help in my PC repair endeavors!!
Now both my 5150 and 5160 both boot without error, and run perfectly!!
Thanks again !!
KL
 
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