Title:			UPDATEMEMC
Author:			Marko Lukat (Marko.Lukat@E-Technik.TU-Chemnitz.DE)
Version:		0.26
Title From:		Documentation
Author From:		Documentation
Version From:		Documentation
Supplier:		Marko Lukat (Marko.Lukat@E-Technik.TU-Chemnitz.DE)
Date:			02/07/95
Keywords:		Memory management software
Shareware:		No
Machine:		Archimedes
Operating system:	RISCOS
Memory requirements:	
Peripherals needed:	MEMC (ie. pre-Risc PC machines)
Other s/ware needed:	
Directory:		micros/arch/riscos/d152
Date mounted/updated:	28/09/95
File names:		updatememc.zip
Unarchived files:	3
Unarchived size:	4 kbytes
Omissions:		
See also:		

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Acquiring the package:

Download the archive file(s) and extract using SparkPlug 2
(see the "tools_help" file in micros/arch/riscos/tools for further info).


Description:

Machines with MEMC1 (VL86C110) control their DRAM refresh through
the SWI "OS_UpdateMEMC". After power on it's set to DURING VIDEO
FLYBACK ONLY. During screen blanking it'll change to CONTINUOUS.
But before Service_ScreenRestored is delivered it's reset to its
original value ... but it isn't! The MEMC refresh state is set to NONE.

Sometimes sound and video DMA will be switched off to get more
speed during vital actions (!ChangeFSI, !GZip). This time the CPU
is the only one which performs memory access. And that's not enough
for a worst case refresh ...

UpdateMEMC installs itself in the module area, and listens out for
every "OS_UpdateMEMC" call. When one goes off, bit 8 will be forced
to 1 (in R0 and R1) i.e. there is no chance to run without refresh.