Excellently cool, bbraun! Thank you!
I don't seem to have permission to download those files. I see that the checksums match. Although file U2 and U3 are reversed, which is no matter, as long as I remember that the deinterleaver's U2 is my U3 and vice versa.
I want to run a Unix diff on them, although that shouldn't really tell me anything new. That is so cool.
So it was a big vs. little endian thing, I think.
And I learned that I have the chip ordering of U1, U2, U3, U4 wrong with respect to the ordering of the data bus. I know how that happened. I used a Beige G3 ROM with just two 32 bit wide chips on it to determine the data order. One of the chips was labeled High and one was labeled Low, and I assumed that referred to the most significant double-bytes, but it apparently referred to the least significant double-bytes.
So instead of Low containing 1 - 32, it contained 1 - 16 and 33 - 48. While High contains 17 - 32 and 49 - 64, where I thought it contained 33 - 64.
This caused me to mis-order the four chips on the conventional ROM.
It never affected me before now, because I've been using data read directly from the chips, and I know which chips the data came from. But now, I need to be able to relate the portions of full words, to their correct 16 bit segments in the ROM chips.
Will I need to install gcc to run the deinterleave program? How difficult will that be? I should be able to throw up or point to that PEx extraction, if you're willing to run your deinterleaver on that.
Then OlePigeon, comes the next part. Put the deinterleaved code on chips. Solder the chips to one of my modules (after desoldering the current occupants) and then off to James in the UK, or to JT more locally for testing. Once it's working, I'll make another one, so they both can have one.
The only thing left to worry about is whether the PEx uses the same byte ordering as the x500/x600. There's really no reason that the data lines on the ROM module can't be swapped in any order from machine model to machine model. But I don't see any way we could determine that without re-borrowing the PEx ROM module from the computer museum where James borrowed it in the first place. And even then, I think I'd have to desolder and read at least one of the chips on the module.
So, fingers crossed that the data lines are in the same order from X500/X600 to PEx. Hmmm. I have the Beige G3 data at home. I could boot it up, run CopyROM on it. And do the same deinterleaver comparison between the chip information and the copyrom extraction. If the Beige G3 (same generation as PEx) uses the same byte ordering as the X500/X600, then there's a very very good chance that the PEx does too.