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NetBSD/mvme68k Frequently Asked Questions

NetBSD/mvme68k Frequently Asked Questions

General Questions

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General Questions

How to handle a dead nvram battery (top)

They are not 'mvme' specific chips, in that there's nothing which needs to be pre-programmed to make them work with a 147. What you need to do, both with a new nvram, or one with a flat battery is to press the abort/reset buttons in the following order to force 147bug to re-initialise the nvram:

  • Press and hold abort

  • Press reset, while still holding abort

  • Release reset

  • 5 seconds later (or when 147bug prompt appears) release abort

You should now set the ethernet MAC address using the lsad command. The address is on a label on the inside of the front panel. Only the last five digits need to be entered. Next, use the mm command to set the 32-bit word at 0xfffe0764 to zero.

What are the jumpers on the backplane (top)

The jumpers on the backplane are for Bus Grant and Interrupt Acknowledge. Some VMEbus boards, like disk controllers, do their own VMEbus I/O instead of using DMA from the CPU. The I/O board requests control of the VMEbus, the arbiter on the CPU board releases control of the VMEbus, and then the arbiter on the CPU sends a Bus Grant signal down the backplane.

There are only 4 Bus Grant levels, and you can have several boards, on the same Bus Grant level. The Bus Grant signal daisy-chains down the backplane through each I/O board. If you have an empty slot you break the daisy-chain.

Backplane manufacturers put jumper pins next to the connectors so you can jumper across empty slots. Unfortunately the jumpers may be to the right or left of a slot depending on the manufacturer.

You may also find that some VMEbus boards don't pass on daisy-chain signals that they don't use. This means that you may have to leave jumpers on even when a board is in a slot.

If the boards are side-by-side without an empty slot between the CPU and the VMEbus boards you may not need any jumpers. That might be worth a try.

My newly installed MVME167 crashes on reboot (top)

This is most likely caused by the NetBSD kernel image loading over the top of 167Bug's workspace in DRAM. The fix is simple; remove jumper 'J1' near the top/front of the MVME167 board. This tells 167Bug to use another area of memory for its workspace.


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