> I just got some very interesting results. > > I examined the bank 8 configuration register contents using the console. It > contained 0x0136, which suggests the cache is not valid. The base address > register contained 0x4000. > > So I booted VMS and modified my code to read the same locations. > Pleasingly the code read back the same values. Which I hope means my code > is correct. > > I then went back to the console to check the bank 0 configuration register > which gave me 0x0069, which indicates it is valid. So there is a good chance I > am reading the right things. > > This I think explains why I get the machine check. While in the console I > changed the bank 8 config register to 0x0137, and then I was able to read and > write to the address of the flashbus index register, but it didn't change the > LEDs when I wrote to the data register, and reading back the data register > gave me a value I didn't write. So there is still something not right, perhaps > the other values in the bank 8 config register, because I don't know what > they mean. However the base address seems correct as it's value is 0x4000 > (the raw value in the register), and this equates to > 0x1.000.0000 based on it being bits 19 upwards in the physical address space. > > I wonder if the SROM failing to read the DROM means that it does not set up > bank 8? >
It turns out that I only needed to flip the bit in the bank 8 config register and I can now access the flashbus. I can write to the LEDs, it turns out that writing a 0 turns the LED on, rather than off, which is why I thought it hadn't worked. I can now do test code for the NVRAM, I will start with repeated reads to see if I get different values on different occasions. Then I will save it and write patterns etc. It may be a checksum that is failing of course. Or the DROM itself, which I can't verify until I get the PLCC adapter for my PROM programmer and someone else to read their DROM. Thanks for all the help I have a way forward for a little while now. Although anyone with one of these machines who could read the DROM would be helpful. I will be able to supply a VMS program to read it, so need to remove it from the machine or to have a programmer. Regards Rob