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@simmiv : Great job on repairing your Compaq! Where did you get a replacement keyboard cable? Mine starts to disintegrate, and I'd need to replace it at some point. Also, FYI, I designed a replacement module for Compaq III battery. It has the advantage of using replaceable CR2477 battery...

I am wondering if people here would be interested in Micro 8088 kits? Possibly the following options: 1. Micro 8088 PCB + chipset - I already did this in the past, and it was some interest. $30 + shipping 2. Micro 8088 PCB + chipset + the pre-programmed Flash ROM and the MCU for the on-board...

You can try that. But in this case, obviously, you won't have the CF card support.

@Betamax80 I am not closely familiar with the PicoMEM board. Are you not seeing any PicoMEM BIOS output at all? Or you can't boot from it? The 8088 BIOS searches the upper memory (D0000-F8000) for BIOS extensions in ascending order. It might be possible that if you swap the addresses of XUB and...

Thank you! That's very useful. It looks that my analysis of the BIOS was correct :) Does it provide any information on how to turn on and off the Caps Lock and Num Lock LEDs? Also it says that the key 84 (num pad Enter) is reprogrammable. Any information on how to do that?

This probably needs to go to the 386/486-based Systems thread

That would be valuable. For my effort, at least the description of the keyboard interface and related schematic would be indispensable

Well, thanks for the help I guess ;) I did disassemble the POST part of the BIOS. Indeed, it appears that the system uses 8251 USART to communicate to the keyboard. The USART's data register is mapped to I/O port 60h, same as the keyboard port on IBM PC/XT and AT, but it allows a bi-directional...

The DMA controller on the PC and XT doesn't use RQ/GT protocol... Instead, when there's a DMA request, the wait logic generates wait states, isolates the CPU from the bus, and lets the DMA do its business. Some clones, particularly chipset based ones, such as FE2010A, PT8010AF, 82C100 do use...

ExPLIT got a bit of a puzzle for me... His colleague has an Ericsson PC, and they tried to run my 8088 BIOS on it. Everything seems to work fine, except of the keyboard. I partially disassembled the INT 9/IRQ1 interrupt handler, and apart from typical PC/XT interaction with the 8255 PPI I/O...

Regarding the interrupt controller type: It appears that some CMOS PICs (82C59 vs. NMOS 8259) generate spurious interrupts when interrupt inputs are floating / not connected anywhere. This doesn't seem to be a problem with some other CMOS PICs... The fix is pretty simple: solder pull-down...

I fixed the issue with the long delay when the PS/2 mouse is not connected a month ago. Please download the latest BIOS. See commit 8fd8cea

8087 co-processor will get hot. But probably not as hot to melt the case ;) There is not that much clearance in the case to install any kind of heatsink... the best I can think of is replacing the plastic door that accesses the CPU/FPU/BIOS with a piece of aluminum, so it will conduct the heat...

Well, I make the Monster FDC. Probably an overkill for what you need it for... If you can solder, you can get the PCB only, and solder a single FDC. If you can't solder... maybe I can do that for you. If you're interested, I can check what would be the price for the components/work.

So it appears that you have confirmed that your board uses the naive turbo switching method using F/C signal, so it suffers from all the issues I've described above. Regarding (4) wait states - it is hardware feature, but if the wait state generator is programmable, it would depend on the BIOS...

Technically it is not the 4.77 MHz clock what peripherals care about. Here is a bit of info about the 8284 and the clock generation in IBM PC, XT, and their clones: The 8284 supports two clock sources, a built-in oscillator, IBM PC and compatibles typically have a 14.31818 MHz quartz crystal...

Yeah, that sounds like a complicated solution ;) Technically, it might be easier to initialize XUB, read the configuration, set floppy/USB floppy emulation configuration, reset interrupt vectors, and then re-initialize XUB again ;)

That would work assuming you have a CF card. Perhaps might be a Book 8088 specific hack... Another potential issue that XUB (XT-IDE Universal BIOS) get initialized a bit later and it assumes (or might assume) that floppy disks configuration, e.g. number of drives, doesn't change after XUB...

It should be not that difficult to check for the FDC presence... probably something like sending a command to FDC, e.g., sense drive status, and checking the result. As far as the boot selection, ideally Book8088 would have a flash ROM or some kind of configuration storage, so that it would be...

A few questions and comments: Did you test your FDC in another system? Or you are assuming it is good since you don't see any new burned traces? When you reprogram your AT29C010A BIOS ROM, does it verify successfully in the programmer? (And then it fails to verify once you put it in Micro 8088...