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Ok thanks - Let me try swapping that out for a 74LS. Will report back.

I have a strange issue with an XT-CF-Lite 4.1 that I recently built. Everything seems to work perfectly, except the write speed is ridiculously slow. I’ve tried different CF cards and different machines but same result. I’ve checked the four logic ICs in my TL866ii and they all test good. I’m...

RL has severely limited retro time recently but I’m hoping I can get back to this a bit more now. I assumed the parity errors were coming from a bad RAM chip, something like this. Did you try swapping the memory board with the working Orchid?

Amazing, this is exactly what I need. What a resource Minuszerodegrees is! IBM 5170 - The 'ground I/O CH RDY' Procedure Just trying to think how best to simulate IOCHRDY being grounded. My 82284 is socketed, so I could carefully lift ARDY (pin 1) out, but then how best to safely pull it high?

Great! I also watched your Youtube video, it certainly shows how picky these boards are.

A productive weekend! Got a proper setup going – IBM 5160 256kb IBM CGA card 16-bit Multi-I/O floppy controller Rancho RT1000B 8-bit SCSI card (no IRQ needed) Did a fresh install of the Orchid drivers on a DOS 3.3 partition and set each board to Port 300h and IRQ7 (to avoid any issues with the...

New memory controllers arrived - and both work perfectly, so both boards now pass the turbochk memory map test. This weekend I will do a full install of the drivers and see if either of them initialise completely. @Digitalman I'm thinking it might be possible to copy across a custom bios to the...

I will have two boards that should at least try to copy across the bios and start the 286... not sure yet what will happen from there! @per - great news on finding the board, thanks for checking the IRQ line. How can I test if my PALs are read-protected?

That 24MHz oscillator is there to drive the 80287 at the higher 8MHz clock speed through the 8284a. The 286 is driven off the 16MHz oscillator - so 8MHz speed after being divided down by 2. If you want the CPU to go faster you'll need to swap out the 16MHz for something faster but given the...

A wild goose chase and then some actual progress this weekend. To cut a long story short, I captured all of the TU-50 inputs pins and everything was the same between the boards, except pin 18 which is the signal coming from another comparator (SN74ALS521N). This is connected to the SW1 jumper...

Ok - Praying that you find it! The PAL chips, memory controller, cpu and gate array all came out the board while looking for the IRQ short. Then contact cleaner in the sockets before everything was reseated, so I think anything connection related can probably be ruled out for now. I've traced...

The mapping does hold through a warm boot, so apologies, that might have caused some issues. With the flaky board, what happens if you boot it and then just let it sit at the command prompt? Will it eventually crash, or it's only if you start to run certain programs? I think I've made some...

Apologies, I should probably have mentioned a couple of things. Firstly I use a SCSI setup, so I'd forgotten about the port clash with XTIDE. Nice job working around it! The other thing is the way that turbochk.com works. It does a very simple set of writes that (somehow) triggers the board to...

Many thanks for the pictures - very interesting. Your boards seem to be a slightly later revision, with the 286 in a plcc package, and one of the pals seems to have an update (labelled TU-21 vs TU-20 on my boards). Also, that pesky via is now gone! Pretty clear that was a factory issue on the...

That's great to hear! Having more boards to compare behaviour to will definitely be helpful. Are you able to attach some pictures of both boards, front and back? Also, I've read the boards are very picky about dos versions, as I think the driver messes directly with some data structures in...

Good point Per on the schematic, I will definitely switch to logical layout now I've got a handle on the routing. I've desoldered the Interrupt Controller from Board 2 but unfortunately the short remains, so somewhere the IRQ5 line and ground must still be touching. Closer inspection of the...

Ok, there have been some developments! I’m still working on tracing the ISA bus through the card (progress so far attached). As you suggested Per, it looks like it will end at the gate array after passing through some of the “TU-“ PAL chips. However, while buzzing out the non-working board...

Thanks Mike and Per. At the moment I'm not getting far enough for code to run on the 286. I think board 1 might be close, but it goes off track soon after the Orchid bios code starts running. However, I've set that board aside for now and am focusing on board 2 which does.. pretty much nothing...

I have two non-working PCturbo accelerator boards that I’ve been trying to revive. These boards are particularly interesting as they do not use a cable to connect to the CPU socket but are instead able to control the 8088 and use it for I/O. On startup the PCturbo board holds the 286 in reset...

https://forum.vcfed.org/index.php?threads/windows-3-0-for-inboard-386-pc.3319/ A lot of messing around in the wayback machine. Find the url in the old index (number 111 in this case).. then Google the thread name...