Introduction
I had to search/wait a long time, but at the end of January 2020 I was able to buy the first 5150 board. Also included was a Tandon TM100-2A without the IBM logo.
Currently I use this model with the ISA Floppy Disk and Serial Controller from Sergej Kiselev and the Lo-tech 1MB RAM board from Kevin R. Williams (texelec).
Basics
Please read this first: IBM 5150 - Basics, for 5150 beginners (minuszerodegrees.net).
Figures
In contrast to the 5160, the 5150 has a cassette interface (2nd DIN plug from above). Below is the relay for the cassette interface. You can hear it (slight crackling) when you copy files from/to the cassette recorder.
What stands out immediately? I changed the BIOS here once. Why? It's kind of annoying when you don't see anything at boot time and wait and wait.
I used the Super PC/Turbo XT BIOS v3.1 from Plasma (Jon Ρetrosky and Ya'akov Miles). Note: The cassette functions do NOT work with the Super PC BIOS! Since my GALEP-5 works fine with the Motorola MCM68764, I use this „old“ EPROM. Otherwise you have to use a 2764-27512 EPROM with adapter.
All banks (0-3 with parity) are completed with 4116 class RAM chips (200 ns). The mainboard works perfectly. Note: These 4116 RAM chips absolutely need -5V from the power supply! Therefore you can not test these chips with „normal“ RAM testers; they do not have -5V.
- 8+1 / MOSTEK MK4116N-3GP / 16 KByte (soldered)
- 8+1 / MOSTEK MK4116N-3GP / 16 KByte
- 8+1 / MOSTEK MK4116N-3GP / 16 KByte
- 8+1 / MOSTEK MK4116N-3GP / 16 KByte
The tantalum capacitors are also working perfectly so far; round about 40 years. Unlike the „64-256“, the „16-64“ has two tantalum capacitors at each bank. So the two boards can be easily distinguished, if you can not read the the appropriate label.
Update 18.01.2021: What is the saying? "Never touch a running system!" For this reason, I struggled for a long time whether to replace the 16V tantalum capacitors. But since I'm doing my current project with this board and often switch it on and off, I replaced all 17 capacitors today. This was no problem with my desoldering gun. Everything is fine. There is nothing more terrible than a tantalum capacitor exploding 50 cm in front of your face.
And this is how the whole test system looks like in the Landmark test (Supersoft ROM Post Diagnostics Version 1.2).
The U28 test failed because in this socket is no system BIOS, it is empty!
In another test setup I changed the IBM MDA graphics card against the IBM EGA card. Note: The IBM EGA card is actually useless for games, because it has only 64 KByte RAM. But for the standard EGA resolution 640x350 with 16 colors (4 bit) at least 128 KByte (exactly 112.000 byte) are needed. A RAM expansion to 128/192/256 KByte is only possible with the "Graphics Memory Expansion Card" (IBM part number 1501201).
ROM BIOS extension at C000 with 64 KByte video RAM and 16 KByte text display memory at B800. The other disadvantage of the IBM EGA card is that it has no parallel interface.