VMEbus-RAM revision 1.1.2.2
1 1.1.2.2 jdolecek $NetBSD: VMEbus-RAM,v 1.1.2.2 2002/02/11 20:08:41 jdolecek Exp $ 2 1.1.2.2 jdolecek 3 1.1.2.2 jdolecek NetBSD/mvme68k: VMEbus RAM card configuration 4 1.1.2.2 jdolecek ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5 1.1.2.2 jdolecek 6 1.1.2.2 jdolecek NetBSD-mvme68k can be configured to support additional RAM boards 7 1.1.2.2 jdolecek accessed over the VMEbus. 8 1.1.2.2 jdolecek 9 1.1.2.2 jdolecek This file describes where to configure your VMEbus RAM and how to 10 1.1.2.2 jdolecek point the kernel in the direction of it. 11 1.1.2.2 jdolecek 12 1.1.2.2 jdolecek The MVME147 board has a fairly primitive VMEbus controller chip. The 13 1.1.2.2 jdolecek mapping of cpu address to VMEbus address is hardwired and so dictates 14 1.1.2.2 jdolecek what can be seen where by the 68030. From the cpu's perspective, A24 15 1.1.2.2 jdolecek space spans 0x00000000 to 0x00ffffff. However, onboard RAM also spans 16 1.1.2.2 jdolecek this space. With 8Mb of onboard RAM, only the top 8Mb of VMEbus A24 17 1.1.2.2 jdolecek space can be seen. With 16Mb onboard, there is no easy way to get at 18 1.1.2.2 jdolecek A24 space at all! 19 1.1.2.2 jdolecek 20 1.1.2.2 jdolecek The other MVME boards have a more sophisticated VMEbus controller 21 1.1.2.2 jdolecek which can remap segments of VMEbus address space anywhere in the CPU's 22 1.1.2.2 jdolecek address space. This document will assume the remap is `transparent', 23 1.1.2.2 jdolecek ie. no translation is taking place. The same restriction as MVME147 24 1.1.2.2 jdolecek applies to these boards in that, without translation, a region of 25 1.1.2.2 jdolecek VMEbus address space is masked by onboard RAM. The size of this region 26 1.1.2.2 jdolecek depends entirely on the size of onboard RAM. 27 1.1.2.2 jdolecek 28 1.1.2.2 jdolecek The best place for VMEbus RAM cards is somewhere in A32D32 VMEbus address 29 1.1.2.2 jdolecek space. Obviously, if your VMEbus RAM card doesn't respond to that space 30 1.1.2.2 jdolecek then you'll have to locate it elsewhere. Typically, you may find it 31 1.1.2.2 jdolecek responds to A24D16 only, in which case the CPU-relative address you need 32 1.1.2.2 jdolecek to specify below will be in the 16MB region starting at 0xZZZZZZZZ. 33 1.1.2.2 jdolecek 34 1.1.2.2 jdolecek For A32D32, choose an address which is resonably close to the end of the 35 1.1.2.2 jdolecek MVME board's RAM. That is, if you have 32MB of onboard RAM, set the 36 1.1.2.2 jdolecek VMEbus RAM board to appear at A32:02000000. 37 1.1.2.2 jdolecek 38 1.1.2.2 jdolecek This starting address needs to be written to the MVME board's NVRAM at 39 1.1.2.2 jdolecek address 0xfffe0764 for MVME147, and 0xff, as follows: 40 1.1.2.2 jdolecek 41 1.1.2.2 jdolecek 147Bug> mm fffe0764 ;L 42 1.1.2.2 jdolecek FFFE0764 00000000? 01000000 <cr> <--- you type 01000000 43 1.1.2.2 jdolecek FFFE0768 00000000? . <cr> 44 1.1.2.2 jdolecek 147Bug> 45 1.1.2.2 jdolecek 46 1.1.2.2 jdolecek Next, you need to configure the end address of VMEbus RAM. Assuming 47 1.1.2.2 jdolecek your RAM card is 8Mb in size, this would be 0x017fffff. You need to 48 1.1.2.2 jdolecek write this value to NVRAM address 0xfffe0768, as follows: 49 1.1.2.2 jdolecek 50 1.1.2.2 jdolecek 147Bug> mm fffe0768 ;L 51 1.1.2.2 jdolecek FFFE0768 00000000? 017fffff <cr> <--- you type 017fffff 52 1.1.2.2 jdolecek FFFE076c 00000000? . <cr> 53 1.1.2.2 jdolecek 147Bug> 54 1.1.2.2 jdolecek 55 1.1.2.2 jdolecek You could obviously combine the above two steps. 56 1.1.2.2 jdolecek 57 1.1.2.2 jdolecek If you have more than one VMEbus RAM card, you must configure them so 58 1.1.2.2 jdolecek that they appear physically contiguous in A32 address space. So, to add 59 1.1.2.2 jdolecek another 8Mb card in addition to the card above, it should be jumpered 60 1.1.2.2 jdolecek to start at 0x01800000. In this case, you would change NVRAM location 61 1.1.2.2 jdolecek 0xfffe0768 to be 0x01ffffff. 62 1.1.2.2 jdolecek 63 1.1.2.2 jdolecek If NVRAM location 0xfffe0764 is zero, the kernel assumes you only have 64 1.1.2.2 jdolecek onboard RAM and will not attempt to use any VMEbus RAM. 65 1.1.2.2 jdolecek 66 1.1.2.2 jdolecek 67 1.1.2.2 jdolecek Some extra notes on VMEbus RAM cards 68 1.1.2.2 jdolecek ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 69 1.1.2.2 jdolecek 70 1.1.2.2 jdolecek So... You've got your nice shiny VMEbus RAM card up and running with 71 1.1.2.2 jdolecek NetBSD, and you're wondering why your system runs slower than it did 72 1.1.2.2 jdolecek with less RAM! 73 1.1.2.2 jdolecek 74 1.1.2.2 jdolecek The simple answer is "Motorola got it wrong". (Or at least that's my 75 1.1.2.2 jdolecek opinion. If anyone can cure the following, let me know!) 76 1.1.2.2 jdolecek 77 1.1.2.2 jdolecek In their infinite wisdom, the designers of the MVME147 decided that 78 1.1.2.2 jdolecek they would disable the 68030's cache on *any* access to the VMEbus. 79 1.1.2.2 jdolecek The upshot is that the cache only works for onboard RAM, not VMEbus 80 1.1.2.2 jdolecek RAM, hence your system runs slower. As far as I can see, the only 81 1.1.2.2 jdolecek way to cure this is to physically cut a trace on the circuit board 82 1.1.2.2 jdolecek and use the MMU to control caching on a page-by-page basis... 83 1.1.2.2 jdolecek 84 1.1.2.2 jdolecek Anyhow, hopefully the above instructions have finally put to rest 85 1.1.2.2 jdolecek the most asked question about the mvme68k port. 86 1.1.2.2 jdolecek 87 1.1.2.2 jdolecek Cheers, 88 1.1.2.2 jdolecek Steve Woodford: scw (a] netbsd.org 89
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