dbert@pogo.ai.mit.edu (Douglas Siebert) (03/14/91)
I read in the April MacUser about the difference between the RAM used in the IIfx and the RAM used in the rest of the Macs. It seems that there are seperate input and output lines "to reduce bottlenecking". I was wondering if anyone knew anything about this....does it increase access times? (i.e. would the access time of a IIfx with 70ns RAM be any different from the access time of a IIfx-clone (if there was such a thing) functionally identical except for using the type of SIMMs found in other Macs? Just curious... Also, anyone know if System 7.0 makes use of the IIfx's DMA capability? I would assume someone with a IIfx and a beta copy of 7.0 would know this. Thanks for anyone taking the time to reply! -- ________________________________________________________________________ Doug Siebert dbert@albert.ai.mit.edu MBA Student (2nd year) The University of Iowa
anders@verity.com (Anders Wallgren) (03/15/91)
In article <1991Mar14.024009.5193@mintaka.lcs.mit.edu>, dbert@pogo (Douglas Siebert) writes: > >Also, anyone know if System 7.0 makes use of the IIfx's DMA capability? I >would assume someone with a IIfx and a beta copy of 7.0 would know this. >Thanks for anyone taking the time to reply! No, but I'm pretty sure that A/UX does. anders
steveh@tasman.cc.utas.edu.au (Steven Howell) (03/24/91)
Well, the mac IIfx does use dual ported RAM, basically, it means it has two lines that data can be sent to the chip thru. There are a couple of diffrent types of this memory, and it does run faster via the ability to read and write more efficently, not via chemical speed levels ie 80ns 100ns etc. The main advantage of this type of memory, is the ability to read and write virtually simultaneously. An obvious example of how this could be used to increase speed would be in the video. Normally only one device could have access to the chip, meaning another would have to wait until the first was finished. But dual port memory can be serviced by two devices, and in a video situation this is ideal, as the video circuit can read the data to be displayed whilst at the same time, but and address behind, the processor can update the new data to be displayed next, all without the two devices needing multiplexed access lines. Basically saves time, and makes things simpler. Anyway, see how that helps you out. Steve h