On 17 Mar 2016 at 11:33, Marcel Kilgus wrote: > [email protected] wrote: > > Thanks for the nice essay. A few remarks: > > > > The "LOWRAM" mode of the Q40/Q60, where read access at $0 to $17FFF > > is mapped to shadow RAM, was mostly used for ROM emulation in the > > early days. The Q60 had to use two 16 bit EPROMs, because the design > > rule was strictly without SMD components. No space saving solution > > with Flash was possible at the time, since the 68060 needs memory > > always 32 bit wide physically, unlike a 68020. The ROM emulation > > saved me from having to UV-erase the EPROMs too often. > > I thought it was a handy tool and could maybe utilized more to > write-protect critical OS code, but so far it isn't and I'm not sure > why. Perhaps for debugging reasons, although I'm pretty sure QMON > actually makes use of sms_wbase to be able to write to low RAM. > > I guess there is no speed difference between this part of RAM and > the rest?
Yes, there's no difference. Only video RAM and non-volatile RAM differ in speed. By the way, on the Q68, FPGA-internal RAM is faster than SDRAM. So if SMSQ/E has a fixed area where speed matters, I could try to map internal RAM there. Peter _______________________________________________ QL-Users Mailing List
