Messages in this thread | | | Date | Sat, 23 Nov 1996 13:35:03 +0200 (EET) | From | Kai M{kisara <> | Subject | Re: Bugs and wishes in memory management area |
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On Sat, 23 Nov 1996, Gerard Roudier wrote: ... > In my flameable opinion, a usable system nowaday needs more than 16 MB, or > at least 16 MB, regardless the O/S it is running. > I disagree. Mybe for software development and general computing but Linux is very nice for more special applications. Examples: - our airborne imaging spectrometer "host" computer doubling as "tape server" when it is in our office between flights (8 MB) - the laptop we use to navigate the flight lines (386 with 4 MB) - my personal laptop (8 MB, running nicely emacs with X, at least I prefer this over running Windows)
IMHO Linux should be useful to similar applications also in future.
... > On the other hand, being given that 128/16=8, 87% IOs will need to be > double-buffered. Doing DMA in that conditions is in my opinion pretty > stupid. > It is instructive to compute how much double buffering really slows down things. Let's assume a peripheral capable of 0.5 MB/s and memory to memory transfer rate of 20 MB/s. With double buffering for all transfers the rate is 0.488 MB/s (assuming double buffering is implemented properly). May be stupid but in many cases it is practical ;-)
Besides, I don't think the issue here is ISA DMA, it is >allocation of a largish chunk of memory that is contiguous in physical memory<. The ISA DMA is special only in that the chunk must be below 16 MB. These kinds of allocations are needed for peripherals that don't support scatter/gather (or don't support enough scatter/gather segments). One example might be a PCI video board that wants to transfer images to a memory buffer.
Kai
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