na103's latest activity

The standard IBM PC and PCXT use the following addresses for the NPU addressing (in Hex format) 0F0 Clears Math Coprocessor Busy Signal...

Not my discovery but read in MSBIO1.ASM from line 82 on how MS thought about IBM :)

there is something strange that I don't understand.:unsure: IC E5, E6, E11 and E17 are present in the part list. However, they are not...

the motherboards rev A and B, vt100 are already present in the bisavers archive. PC100B memory extension is in my repo github and also...

What I found in the pile of paper - mostly multiple paper copies in mixed quality PC100 Motherboard 54-15486-01 PC100B Motherboard...

I did not read through the whole thread - but I got the impression that no complete circuit diagrams of the adapter exist ? Many years...

Hi Guenter, once again you save the day. thank you, thank you so much for these schematics. now I have a few nights to spend awake...

from what I've seen when a 100B memory is installed via the 8087 adapter on the Rainbow 100A, MEM PRES remains high. this means that the...

however this does not matter for RAMbow. I can eliminate E29 and manage the addressing with a GAL logic and a jumper to set when RAMbow...

it seems that before the multiplexer E27 the address lines (A16 - A19) were probably modified to overcome the memory gap problem by...

I have attached the Intel x86 and/or x88 minimum mode Hold and Hold Ack to RQ and GR conversion Circuit. This circuit some 3 rd party...

I have attached the enhanced intel 8087 Dos interrupt circuit that a lot of the 80X88/86 based Unix/Dos Box hybrids use. The clone board...

Right on a replacement for the old Rainbow 100 Memory with a future 8087 adapter on board is under redevelopment with 1M of DRAM...

I don't want to create false expectations, I'm working on it. at the moment I have modified the board with nine 1Mbit DRAM and removed...

Hi there -- OK, so yesterday I did some testing and poking around. I had built a little fixture to allow me to mess with the outputs of...