VMEbus-RAM revision 1.1.4.2
1 1.1.4.2 nathanw $NetBSD: VMEbus-RAM,v 1.1.4.2 2002/02/28 04:10:52 nathanw Exp $ 2 1.1.4.2 nathanw 3 1.1.4.2 nathanw NetBSD/mvme68k: VMEbus RAM card configuration 4 1.1.4.2 nathanw ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5 1.1.4.2 nathanw 6 1.1.4.2 nathanw NetBSD-mvme68k can be configured to support additional RAM boards 7 1.1.4.2 nathanw accessed over the VMEbus. 8 1.1.4.2 nathanw 9 1.1.4.2 nathanw This file describes where to configure your VMEbus RAM and how to 10 1.1.4.2 nathanw point the kernel in the direction of it. 11 1.1.4.2 nathanw 12 1.1.4.2 nathanw The MVME147 board has a fairly primitive VMEbus controller chip. The 13 1.1.4.2 nathanw mapping of cpu address to VMEbus address is hardwired and so dictates 14 1.1.4.2 nathanw what can be seen where by the 68030. From the cpu's perspective, A24 15 1.1.4.2 nathanw space spans 0x00000000 to 0x00ffffff. However, onboard RAM also spans 16 1.1.4.2 nathanw this space. With 8Mb of onboard RAM, only the top 8Mb of VMEbus A24 17 1.1.4.2 nathanw space can be seen. With 16Mb onboard, there is no easy way to get at 18 1.1.4.2 nathanw A24 space at all! 19 1.1.4.2 nathanw 20 1.1.4.2 nathanw The other MVME boards have a more sophisticated VMEbus controller 21 1.1.4.2 nathanw which can remap segments of VMEbus address space anywhere in the CPU's 22 1.1.4.2 nathanw address space. This document will assume the remap is `transparent', 23 1.1.4.2 nathanw ie. no translation is taking place. The same restriction as MVME147 24 1.1.4.2 nathanw applies to these boards in that, without translation, a region of 25 1.1.4.2 nathanw VMEbus address space is masked by onboard RAM. The size of this region 26 1.1.4.2 nathanw depends entirely on the size of onboard RAM. 27 1.1.4.2 nathanw 28 1.1.4.2 nathanw The best place for VMEbus RAM cards is somewhere in A32D32 VMEbus address 29 1.1.4.2 nathanw space. Obviously, if your VMEbus RAM card doesn't respond to that space 30 1.1.4.2 nathanw then you'll have to locate it elsewhere. Typically, you may find it 31 1.1.4.2 nathanw responds to A24D16 only, in which case the CPU-relative address you need 32 1.1.4.2 nathanw to specify below will be in the 16MB region starting at 0xZZZZZZZZ. 33 1.1.4.2 nathanw 34 1.1.4.2 nathanw For A32D32, choose an address which is resonably close to the end of the 35 1.1.4.2 nathanw MVME board's RAM. That is, if you have 32MB of onboard RAM, set the 36 1.1.4.2 nathanw VMEbus RAM board to appear at A32:02000000. 37 1.1.4.2 nathanw 38 1.1.4.2 nathanw This starting address needs to be written to the MVME board's NVRAM at 39 1.1.4.2 nathanw address 0xfffe0764 for MVME147, and 0xff, as follows: 40 1.1.4.2 nathanw 41 1.1.4.2 nathanw 147Bug> mm fffe0764 ;L 42 1.1.4.2 nathanw FFFE0764 00000000? 01000000 <cr> <--- you type 01000000 43 1.1.4.2 nathanw FFFE0768 00000000? . <cr> 44 1.1.4.2 nathanw 147Bug> 45 1.1.4.2 nathanw 46 1.1.4.2 nathanw Next, you need to configure the end address of VMEbus RAM. Assuming 47 1.1.4.2 nathanw your RAM card is 8Mb in size, this would be 0x017fffff. You need to 48 1.1.4.2 nathanw write this value to NVRAM address 0xfffe0768, as follows: 49 1.1.4.2 nathanw 50 1.1.4.2 nathanw 147Bug> mm fffe0768 ;L 51 1.1.4.2 nathanw FFFE0768 00000000? 017fffff <cr> <--- you type 017fffff 52 1.1.4.2 nathanw FFFE076c 00000000? . <cr> 53 1.1.4.2 nathanw 147Bug> 54 1.1.4.2 nathanw 55 1.1.4.2 nathanw You could obviously combine the above two steps. 56 1.1.4.2 nathanw 57 1.1.4.2 nathanw If you have more than one VMEbus RAM card, you must configure them so 58 1.1.4.2 nathanw that they appear physically contiguous in A32 address space. So, to add 59 1.1.4.2 nathanw another 8Mb card in addition to the card above, it should be jumpered 60 1.1.4.2 nathanw to start at 0x01800000. In this case, you would change NVRAM location 61 1.1.4.2 nathanw 0xfffe0768 to be 0x01ffffff. 62 1.1.4.2 nathanw 63 1.1.4.2 nathanw If NVRAM location 0xfffe0764 is zero, the kernel assumes you only have 64 1.1.4.2 nathanw onboard RAM and will not attempt to use any VMEbus RAM. 65 1.1.4.2 nathanw 66 1.1.4.2 nathanw 67 1.1.4.2 nathanw Some extra notes on VMEbus RAM cards 68 1.1.4.2 nathanw ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 69 1.1.4.2 nathanw 70 1.1.4.2 nathanw So... You've got your nice shiny VMEbus RAM card up and running with 71 1.1.4.2 nathanw NetBSD, and you're wondering why your system runs slower than it did 72 1.1.4.2 nathanw with less RAM! 73 1.1.4.2 nathanw 74 1.1.4.2 nathanw The simple answer is "Motorola got it wrong". (Or at least that's my 75 1.1.4.2 nathanw opinion. If anyone can cure the following, let me know!) 76 1.1.4.2 nathanw 77 1.1.4.2 nathanw In their infinite wisdom, the designers of the MVME147 decided that 78 1.1.4.2 nathanw they would disable the 68030's cache on *any* access to the VMEbus. 79 1.1.4.2 nathanw The upshot is that the cache only works for onboard RAM, not VMEbus 80 1.1.4.2 nathanw RAM, hence your system runs slower. As far as I can see, the only 81 1.1.4.2 nathanw way to cure this is to physically cut a trace on the circuit board 82 1.1.4.2 nathanw and use the MMU to control caching on a page-by-page basis... 83 1.1.4.2 nathanw 84 1.1.4.2 nathanw Anyhow, hopefully the above instructions have finally put to rest 85 1.1.4.2 nathanw the most asked question about the mvme68k port. 86 1.1.4.2 nathanw 87 1.1.4.2 nathanw Cheers, 88 1.1.4.2 nathanw Steve Woodford: scw (a] netbsd.org 89
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