Omega Read ME Updated 1/7/2003 ============= Notes ===== 1. Omega hardware has an emulated IOMD, in the 7500FE variant, ie with both keyboard and mouse using PS/2. Therefore algorithms that rely on the IOMD ident version register to identify the CPU will get the wrong answer. IOMD is NOT part of the cpu. The CPU has its own ident register, which of course will correctly identify that it is a StrongARM. 2. Mode Setting. The video bandwidth is normally set at 960,000 Kbytes/sec, although the memory limit is technically 1064,000 Kbytes/sec, it leaves nothing for the CPU... There is NO VRAM as such, so in ...Predesk.Configure.!Run, use the following settings: /.BandLimit 960000 76000 152000 960000 Current system does not support black/white video modes. A default mode file is provided in the resource filing system at "Resources:$.MicroDigital.Video.ModeDefs" to allow other modes to be selected when the desktop boot has not happened. Use of TV frequency monitors is still technically possible but should not be encouraged. Modes selected with colour numbers are converted into the equivalent size, frequency and colour depth (except 1bpp modes are set at 2bpp), and are then looked up in the mode definition file. If a suitable definition is not found then an error is generated (Display application suppresses the error). At power-up, mode 28 is selected initially. Video can be generated equally well from anywhere within SDRAM, but obviously the frame buffer must be contiguous in the physical map. 3. SDRAM Omega supports up to 1GB of PC133 SDRAM, either in registered or unbuffered forms. Initialisation of the SDRAM is done by the MicroDigital Prekernel code prior to starting Risc OS, so the various IOMD registers that set speeds etc for FP/EDO RAM, are actually mapped into SRAM and do *nothing*. The hardware should cope with any PC133 SDRAM DIMM, subject to there being a maximum of about 17 chips to drive in total: for this purpose registered DIMMs count as "1 chip" per DIMM. Each DIMM has one or two banks, usually on one or two sides respectively. The hardware supports mixed registered with unbuffered, but the current PreKernel does not reliably identify this configuration. For compatibility with existing Risc OS ROM images, the first 64MB of each bank of memory is mapped into the same place in physical memory as a Risc PC, ie starting at :- &100 00000, &140 00000, &180 00000, &1C0 00000. To access all 1GB, the SDRAM is also mapped in four banks of 256MB at:- &400 00000, &500 00000, &600 00000, &700 00000. There is a new release of Risc OS in progress to support 1GB properly. 4. Power-off Because Risc OS 4.03 does not generate a Shutdown confirm dialog following the SWI "TaskManager_Shutdown", Omega starts a shutdown sequence from the power button interrupt by issueing a ctrl-shift-F12 (only within the desktop). If the Service Call "Service_ShutDownComplete" is sent out, then the power will be turned off immediately. We are in discussions with Select developers about better support in the TaskManager.