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5150 Memory Errors with AST SixPack Plus Adapter assistance please

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eebuckeye

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I picked up a 5150 and have spent my night trying to figure out memory configurations.

When I first got the 5150 it had the AST SixPack Plus adapter installed with 1 bank and the computer reported 128k memory.

I removed the AST SixPack Plus and got a 1001 201 error when booting which I thought was odd. I checked SW1 on the motherboard and got the following:

- 3 on, 4 off 1001 201 49152 bytes
- 3 off, 4 off 1001 201 will not boot

It is a PC1 motherboard and all memory banks are full. With the AST SixPack Plus adapter installed I got 128k. The SixPack Plus was set to start at 64k (dip switches 1,2,3 are off)

I then tried the following AST dip switch configurations per the users manual:

- AST 4,5 off 6 on – bank 1 only active (bank 1 and 2 populated), no boot error, 131,072 bytes free
- AST 4,6 off, 5 on – bank 1-2 active with 2 banks memory, no boot error 131,072 bytes
- AST 4,6 off, 5 on – bank 1-2 active with 2 banks memory, no boot error 131,072 bytes (same as previous but swapped with different memory)
- AST 4, off, 5-6 on – bank 1-3 active with 3 banks memory, no boot error 131,072

I do not understand why I do not report at any time greater than 128k of memory. I do not receive boot errors when the AST is installed either.

I am using DOS 1.1 chkdsk to see the available memory.

Any suggestions please?

Thank you!
 
What does SW2 look like? IIRC, to run the system with only 64kB of RAM, SW2 would also need to be set to 64kB. I think you have it set to 128KB of RAM on SW2. This means that if SW1 is set to less than 64kB, the system will stop counting at the set level. If set to 64kB with SW1 but even more on SW2, the system will lock up as it tries to access non-existent memory.

With the Six Pack Plus and 3 filled banks, SW2 would need to be set to a higher value of 256kB to use all the memory.
 
Last edited:
SW2: 1,3,4 on - 2,5,6,7,8 off

I am confused on two items:

1) Why am I getting a memory error without the AST adapter installed?
2) Why does the memory never increase when I enable additional banks on the AST adapter? I do not receive memory errors.

I am using DOS 1.1 with chkdsk to check available memory.
Thanks!
 
http://www.minuszerodegrees.net/5150/ram/5150_ram_16_64_SW2.jpg indicates that you have SW2 set for 128kB. (And you have the earlier 544KB max BIOS.)

1) The memory error is a configuration issue. The system thinks there should be 128kB but there isn't without the AST card.

2) Need to update SW2 to the total memory of the AST card plus motherboard. The 5150 is a very limited design; it does not automatically detect added memory. Flipping switch 3 to off on SW2 should solve the problem if I am correct that the AST card has 3 banks of 64kB each.
 
Ah! That is great information!! Thank you!

The AST adapter has 6 banks of 64k so it looks like 448k would be my max and I would need to set SW2 to 1 - 1 - 0 I believe if I use all the AST banks?
 
I think that you have the correct settings.

If you do put that much memory in the system, I suggest switching to DOS 2 or 3 because very few DOS 1 applications would use more than 128 kB.

If you are sticking with early DOS applications, note that some had problems if the RAM exceeded 512kB so a second memory expansion card may not be helpful.

One other note since you have such an early PC, the included 8088 CPU may not work with an 8087 coprocessor. You won't need an 8087 unless you want to run IBM's APL for the PC.
 
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