Talk:Shadow RAM (Acorn)

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I'm pretty sure that what I've written is correct, given my experience with Acorn's memory model. However, I can't cite a reference as my books here (primarily, the Advanced User Guide) predate Shadow RAM. A good reference is probably the Master Series User Guide, but I no longer have, or have access to, a BBC Master. Ghiraddje 17:12, 27 May 2007 (UTC)[reply]

Master Shadow RAM[edit]

I asked BeebMaster about the article:

I think the general thrust of it is correct but, like you, I'm not sure about the final paragraph.

I think there may be some confusion between the Master shadow RAM and the private RAM. There's 32K of additional RAM in the Master 128 but only 20K of this is shadow RAM since 20K is the maximum screen size and the other 12K is "private RAM" which can be claimed by paged ROMs for buffering, mainly by filing system ROMs for file transfer operations.

Is this what you mean, Shakespeare? Do you agree? I'm not as familiar with the Master so I will defer this one for the moment (otherwise I'd have to look up a Master manual on the Web).

Please also note that the plural of "ROM" is "ROMs" (lowercase 's')! And you would be really advised to spell/grammar-check your typing!

Only 20K was ever "shadow ram". On the B+ the remaining 12K could be accessed by setting a large value (much larger than the highest valid "rom number") to map it into the "sideways rom" area of the memory map but wasn't used for anything by the system software. On the master the extra 12K was split up and put to work. A 4kB section mapped over the paged roms was used as operating system workspace. The other 8kB was mapped over the bottom half of the operating system and used for a mixture of more operating system workspace and workspace for sideways roms (especially filling systems). This allowed various extra OS features to be implemented and allowed "page" (the bottom of user memory) to remain at E00 with both DFS and ADFS roms enabled. http://maben.homeip.net/static/S100/BBC/BBC%20Bplus%20Service/B+ServManual.rtf http://www.8bs.com/submit/acornappspdf/037.pdf http://www.cloud9.co.uk/james/BBCMicro/Documentation/Master.html Plugwash (talk) 03:59, 24 May 2016 (UTC)[reply]