[理工] 100交大OS+計組

[Transfat (Transfat)]

[100交大計組] 11(b)
Before DMA transfer. DMA controller must notify processor by supplying identity of the device,operation, memory addrss, number of bytes to  transfer,etc.
我知道DMA在傳data之前要先去跟CPU問說可不可以傳，我想問這題錯在DMA是都不會去提供這些資訊嗎還是？

[100交大OS] 05.

Consider a tiny paging system has 16KB physical memory, and the frame size is 1KB. Let the logical address have 16 bits. The page table uses single-level direct index. Which one of the following is not correct?
(c)There are 16 entries in the page table
(e)The page table requires 320 bits , including the vaild-invaild bits.

竟然卡住了，這題應該假設page size=frame size去算（吧）,所以page offset=10,page index+tag=16-10=6
frame number=4 bits(因為有16個frame),想問(c)和(e)是？

謝大家

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推 yupog2003: OS(5)，page index有6個bits，所以page table有2^6=64
→ yupog2003: 個entry
→ yupog2003: physical memory內有16KB/1KB=16個frame，所以PPN需要
→ yupog2003: 4個bits，加上valid-invalid bit，一個entry需5個bits
→ yupog2003: page table就需要64*5=320bits
推 yupog2003: 100-11(b)應該是processor去notify DMA controller?
→ kyuudonut: 龍書是寫CPU設定device controller, 後者在設定DMA
→ kyuudonut: 我覺得有點奇怪就是
→ Transfat: 阿我想起來了，這些東西是CPU去設定device controller,
→ Transfat: Device controller再下command給DMA
→ yupog2003: 我看到龍書的一段話：
→ yupog2003: To initiate a DMA transfer, the host writes a DMA
→ yupog2003: command block into memory.This block contains...
→ yupog2003: (就是那些東西).The CPU writes the address of this
→ yupog2003: command block to the DMA controller,then goes on
→ yupog2003: with other work.
→ yupog2003: 這邊的host應該就是device controller的意思？
→ yupog2003: 不過直接看龍書給的圖的確是T大和k大那樣說的沒錯
→ yupog2003: 不過這裡又寫CPU writes the address of this command
→ yupog2003: block to DMA controller，感覺又有點像CPU在做的
→ yupog2003: 張凡的書是直接寫：處理器對DMAC進行設定，包括提供...
→ yupog2003: (就是那些東西)，這樣感覺有點差異，不過都不會是DMA去
→ yupog2003: notify CPU就是了
推 kyuudonut: 對阿 我覺得超怪的 龍書有兩種寫法 但應該還是要看
→ kyuudonut: 實作啦 @@
→ yupog2003: 也許那段話是包含在圖的第三個步驟也說不定XD
→ yupog2003: 感覺我好鑽牛角尖...