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IBM 5150 & 5161 reactivation

T

Techcollect

Member
Joined
Apr 24, 2012
Messages
10
Location
Germany
Hello all,

I just picked up a 5150/5151/5161 combination at a local estate and I'm working on getting this set reactivated.

The 5150 from late 1983 has a 16-64 kB mobo with 64 kB and the 10/27/82 BIOS, MDA, floppy controller and a 64-256 kB memory expansion card with 256 kB.

After a bit of cleaning and checking the settings of jumpers and switches, I fired it up, no POST errors, but the memory count only showed:

62940 Bytes free

Which is less than the 64 kB onboard.

I took all cards except MDA out, deactivated the floppies, set the switches to 64 kB only and the count went to:

61404 Bytes free

Again less than 64 kB.

Does BASIC use part of the RAM for something?

I then put the expansion card back, checked different jumper configurations (here some POST errors occured), but with proper settings (IBM_5150_Guide_to_Operations_6322510_APR84) and a working BASIC the count remains at 62940 Bytes.

I don't have a diagnostics floppy yet (5,25" drive not yet installed on the XP machine), but maybe someone out there has a clue...

Thank you.

Chris
 
Whoah. That message "Bytes Free" looks like the ROM BASIC sign-on message. The number is pretty much what one would expect. ROM BASIC keeps all of its data in one segment, so, with overhead, there's about 62K, give or take, available for programs.

But that has nothing to do with the amount of memory available to non-BASIC programs, such as DOS.
 
Ok, so it's pretty much the same as with my old Amstrad CPC464 - BASIC uses RAM space.

Any idea how to test the memory expansion card?

Is it usefull to remove RAM from the banks and check each bank separately - though no POST errors occur?

Or rather wait till I get my diagnostics and DOS boot disks?
 
Wait until you have a DOS boot disk, then typing mem will let you see the available memory.
Any available memory will be tested by the 5150 on startup.

I would not recommend moving chip memory unless it's actually necessary.
 
The "bytes free" in Cassette BASIC (or Disk BASIC, for that matter) will always show slightly less than 64K even if you have the full 640K installed, so it's really of no relevance, except maybe to show that you have at least 64K installed and recognized by the BIOS -- i.e. if only 32K is being recognized for some reason, then it'll show a few K less than 32K.
 
Thanks guys!

I forgot that the PC doesn't have the usual memory count...

I just checked with an old DOS 3.30 disk I remember lying around.

Unfortunately this version doesn't include the MEM command, but since 3.30 wouldn't load with only 64 kB and does with the expansion card installed I assume the card works.

So much for today.

Tomorrow I'll hook up the 5161.
 
Techcollect said:
I just checked with an old DOS 3.30 disk I remember lying around.

Unfortunately this version doesn't include the MEM command, but since 3.30 wouldn't load with only 64 kB and does with the expansion card installed I assume the card works.
Click to expand...

CHKDSK will tell you how much RAM you have installed (and how much is available with DOS loaded into memory).
 
Congrats on the find! Hopefully you didn't end up paying what the last set I saw go for on ebay... YEESH! :)

Don't forget... pictures! We like pictures! :)
 
Maverick1978 said:
Congrats on the find! Hopefully you didn't end up paying what the last set I saw go for on ebay... YEESH! :)

Don't forget... pictures! We like pictures! :)
Click to expand...

Thanks. Well, I guess it was a bargain. I paid less for the set than others bid for a working ST-412.

It was local pickup only in a rural part of Germany, hence why not too many people bid.

As for the pictures: I'm currently resizing some.
 
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