Dissection time!

Ok, as I’m probably the last person on this planet fiddling around with the NumberSmasher i860, it was either “help yourself” or bust.

Given the fact that there’s an INMOS C012 on the card I tried my luck with the standard address of 0x150 and checked it with DOS’ crappy old ‘debug’. To my surprise I was able to talk to the C012, so it was very worth to investigate further.
So out went the good ol’ EPROM programmer and the EPROM of the card was dumped into a file.
I have 3 of those boards, two having a label on the EPROM saying “v1.1” and “BOOT_B2”. Both are identical… if you happen to own a NumberSmasher with a different label, get the dumpfile here for comparison.

That was easy, now the harder part: Disassembly. I had to revive my i860 machine language skills again, so it took me 2 days (on and off) to get a full understanding, what’s happening in there.
For those i860 assembly geeks among you, here‘s the fully commented code.

This “BIOS” is actually pretty simple. It’s just what I’d call a “PeekPokeStarter”. The main loop is waiting for a ‘command’ coming in by the way of the C012. This command can be either “0” or “1” as mentioned in the article on the previous page.

“0” means POKE (ie. write) and expects 4 bytes for the address and 4 bytes of data to be written (Both LSB first, Intel-style). So the full command reads: 0 00 00 00 20 78 56 34 12 or “write to address 0x20000000 the value 0x12345678”

So in consequence “1” means PEEK (ie. read) which just needs 4 bytes for the address to be read. The command would then be 1 00 00 00 20 or “read from 0x20000000”. The “BIOS” will then put 4 bytes to the C012 port at 0x150, which requires 4 reads from the PC side getting “78”, “56”, “34” and “12”.

Pretty simple, huh? But how can I start a program after it’s been painstakingly poked into the NumberSmashers RAM? Here’s the trick:

Poking to address 0x00000000 means start from the address given as data. E.g. “write to address 0x00000000 the value 0x20000000” is actually “start from 0x20000000”, or as command-chain: 0 00 00 00 00 00 00 00 20 – so beware of poking to 0!
Also, starting a program seems to disable the EPROM, so communication to the C012 is cut off if the running program isn’t handling this itself.

That’s about it. Nothing more in the “BIOS”… that’s why only 495 bytes(!) of the 8K EPROM are actually used. This simplicity leads to a very simple memory-map:

Base =  0xF8000000
C012-InData = [base] + 0x07
C012-OutData = [base] + 0x0F
C012-InStatus = [base] + 0x17
C012-OutStatus = [base] + 0x1F

Next task: Get a program running on the NumberSmasher.

[11/11/10] Great News…again! It was easier than expected… the first program running on the NumberSmasher-860! So read on in the next post…

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