nemeth@gpu.utcs.utoronto.ca (Gabe Nemeth) (04/06/90)
Hi. I thought I'd bounce this idea off the net so here goes: I want to speed up the 68000 processor in my machine from 8 to 16 MHz but due to some custom chips etc., I can't just plop in a faster processor with a new clock (or add a 68030 :-(). I have added appropriate glue logic but this shifts the clock back and forth from 8 to 16 MHz depending on th bus state but this method only gives about a 12MHz performance. So - would it be possible to build a cache to hook a fast processor to a slower bus by using dual ported ram? The idea would be to have all data go through a ram that could be simultaneously addressed by both the cpu and the bus. That way data could accumulate in the ram until the system bus can use it. Processor reads from memory would simply wait for data to become available (slowing system throughput). I guess DMA would have to be done at the slower bus rate unless the ram was the same size as the maximum DMA block. Think this is worth trying? Any other ideas for making a simple 68000 cache system? Thanks in advance! /gabe
henry@utzoo.uucp (Henry Spencer) (04/06/90)
In article <1990Apr6.042829.8824@gpu.utcs.utoronto.ca> nemeth@gpu.utcs.utoronto.ca (Gabe Nemeth) writes: >I want to speed up the 68000 processor in my machine from 8 to 16 MHz >but due to some custom chips etc., I can't just plop in a faster processor >with a new clock (or add a 68030 :-()... Frankly, from your description I'd be wondering whether it *is* time to think about a 68020 or 030. Your plans are taking the 68000 farther and farther from direct control of the bus; it doesn't sound like it would be lots harder to just switch to one of the better processors. They are capable of running on the narrower bus, and apart from being faster in various other ways, have built-in caches. -- Apollo @ 8yrs: one small step.| Henry Spencer at U of Toronto Zoology Space station @ 8yrs: .| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
pophal@nicmad.UUCP (Gerry Pophal) (04/12/90)
In article <1990Apr6.042829.8824@gpu.utcs.utoronto.ca> nemeth@gpu.utcs.utoronto.ca (Gabe Nemeth) writes: >Hi. I thought I'd bounce this idea off the net so here goes: >I want to speed up the 68000 processor in my machine from 8 to 16 MHz >but due to some custom chips etc., I can't just plop in a faster processor >with a new clock (or add a 68030 :-(). I have added appropriate glue logic >Any other ideas for making a simple 68000 cache system? Check out the magazine EDN July 21, 1988 pages 84-87. It is a special issue of design ideas volume II. The article describes adapting a 68020 into 68000 systems. I have also seen instructions on converting an 8mhz 68000 mac into a 16mhz version. gp