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meega · 15 January 2009, 21:53

IF the simm is rated 60ns (or faster, unlikely to be the case) THEN you can use the 60ns setting, but there is no harm in running it slower (at 70ns speed). If the simm is rated 70ns then you ought to leave that jumper open, else you might well see errors. You should not use any simms rated slower than 70ns in a MkIV - so 80ns simms are no good.

If you have the SCSI kit and you have more ram in the second slot that the kit provides then you must use 70ns to ensure good timing, regardless of the speed of the fitted simms.

There is nothing wrong with closing the MapROM jumper, I run mine that way. The speed difference is not all that much in most circumstances and if you only have a small capacity simm then the extra 0.5MB of available ram might be more valuable than the slight OS boost.

15 January 2009, 21:53	#42
meega Registered User Join Date: Dec 2007 Location: Oooh what a feeling yeaaah dancing on the ceiling Posts: 314	IF the simm is rated 60ns (or faster, unlikely to be the case) THEN you can use the 60ns setting, but there is no harm in running it slower (at 70ns speed). If the simm is rated 70ns then you ought to leave that jumper open, else you might well see errors. You should not use any simms rated slower than 70ns in a MkIV - so 80ns simms are no good. If you have the SCSI kit and you have more ram in the second slot that the kit provides then you must use 70ns to ensure good timing, regardless of the speed of the fitted simms. There is nothing wrong with closing the MapROM jumper, I run mine that way. The speed difference is not all that much in most circumstances and if you only have a small capacity simm then the extra 0.5MB of available ram might be more valuable than the slight OS boost.