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IBM 5150 Memory configuration

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MaTel

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Since yesterday I am a owner of a ibm 5150 PC. About the memory configuration i am a little bit confused.
The mainboard is a 64-256KB version. Bank 0 has soldered chips, bank 1 has socket chips, bank 2 and 3 have empty sockets. I think the mb has 128kb on board?
I want to insert an Diamond Flowers PBME-576 memory expansion with 512kb on board. Must I change the dip-switch-settings on the mainboard or are they only for the mainboard memory only?
 
It should say how much ram you have when it boots up. Also the switches must be set to the correct number, or the amount you wish it to use. I don't know the memory card, but I would guess it has to be set to continue memory addresses where the MB left off.
 
Switches 3 and 4 on SW1 are set to the number of RAM banks on the motherboard that are populated. So you would set 3=off, 4=on. Two banks of 64K is 128K. You would set your 512K memory expansion card to start at address 128K, thus occupying addresses 128K to 640K.

The SW2 switches are set to the total amount of RAM (motherboard + expansion cards), in this case, 640K (1=on, 2=off, 3=on, 4=on, 5=off).
 
I just remembered something. Being a 64K-256K motherboard, the ROM will be the third revision (U33 part number = 1501476). A peculiarity of that ROM is that is requires all four banks of RAM be populated.

So you may need to first populate all 4 motherboard banks (4 x 64K = 256K), then set switches 3 and 4 on SW1 to off, then configure your RAM card to provide 384K of RAM between addresses 256K and 640K, then set SW2 switches for 640K.
 
modem7 said:
I just remembered something. Being a 64K-256K motherboard, the ROM will be the third revision (U33 part number = 1501476). A peculiarity of that ROM is that is requires all four banks of RAM be populated.

So you may need to first populate all 4 motherboard banks (4 x 64K = 256K), then set switches 3 and 4 on SW1 to off, then configure your RAM card to provide 384K of RAM between addresses 256K and 640K, then set SW2 switches for 640K.
Click to expand...

No, the mainboard works fine if only Bank 0 and Bank 1 is populated and the rest comes from a memory expansion. U33 is populated with 1501476.
Is it normal that a IBM 5150 has no memory count on the display at startup?
 
I know this is an older post, but I want to make sure I understand something. From what is said here, does that mean that even the 64Kb 5150 is upgradable to 640Kb of memory?
 
bettablue said:
I know this is an older post, but I want to make sure I understand something. From what is said here, does that mean that even the 64Kb 5150 is upgradable to 640Kb of memory?
Click to expand...

Yes, but you need to update the ROMs. The 4/24/81 and 10/19/81 ROMs only recognize up to 544K of RAM. The 10/27/82 ROMs, which came on the 256-640K motherboard and was provided by IBM as an upgrade for the 16-64K motherboard, will recognize the full 640K.
 
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