Alpha Systems 256K upgrade 1200XL

[rockdoc2010]

So I was dusting off a unit for sale and came upon a 1200 that has the alpha systems 256K memory upgrade installed.

I am sure it is probably a Rambo knock-off and I don't care.

 

My question is why the self test don't see more than 3 16K bars?

 

Is There a basic peek that I can try to determine my memory?

 

Thank You!

 

[TGB1718]

Self test will only test stock memory, it has no knowledge of any expansion RAM.

 

To test the extra RAM (if it's a RAMBO), you would need to

POKE a value at $4000,

PEEK PORTB and save it,

POKE PORTB with a suitable value to enable an 8K windows at address $4000 to $7fff (bits 2 and 4 must be '0' and bit 1 must be 1)

POKE a different value into $4000,

PEEK the value back, make sure its the same value so you know it's RAM

restore PORTB and PEEK $4000 and see the result you previously stored there.

 

You can then do this for each bank

 

I believe these values will work:-

 

List of free banks (index=regvalue):

 

4=$E3   5=$E7   6=$EB   7=$EF
8=$C3   9=$C7  10=$CB  11=$CF
12=$A3  13=$A7  14=$AB  15=$AF
16=$83 17=$87 18=$8B 19=$8F

 

Don't worry about the index number, for a 1200XL you can subtract 4,

I got these values from a 130XE, so banks 0 to 3 are the extra memory in the 130XE.

You just use the Hex numbers into PORTB

[adam242]

SimCheck is your friend.

[_The Doctor__]

XRAM, etc as well