This post is addressed to users of Ersatz-11. Many of you are aware that my addiction is running software for the PDP-11 architecture under the RT-11 operating system. While those of you who use RSX-11 or RSTS/E may also be interested, I am not sure how to port the PDP-11 portion of the software to a user environment under RSX-11 or RSTS/E. Specifically, explicit access to the IOPAGE Registers is required. RT-11 allows access either via the Current Data space if the user is able to run using an unmapped monitor or as a privileged job under a mapped monitor. In addition, if the user is running as a Virtual Job using VBGEXE under a mapped monitor, it is possible to use the .Poke EMT request to make the IOPAGE Registers available via the Previous Data space. If it is possible under RSX-11 or RSTS/E to meet that requirement, then the enhancements specified in this post can also be used under these two operating systems. About 5 years ago, John Wilson made available a plugin named EMEM.DLL which allowed an RT-11 user to explicitly access the memory of the PC via four IOPAGE Registers. Early in September of 2008, John made the final changes to allow EMEM32.DLL to perform the same explicit access of PC memory under V5.2 of E11. While John's version makes only 8 MB of such memory available, it is possible to use WatCom to assemble the source code and link the OBJ file with many enhancements, including any memory size that the operating system (in this case DOS or some version of Windows) and hardware on the PC supports. With the current systems being run under Windows XP, I am confident that 1 GB of memory can be used. My interest is to use an enhanced EMEM32.DLL when sieving for Prime Numbers as one example where very large work RAM will substantially improve the speed of an algorithm. The present 4 IOPAGE Registers are used in the following manner: Mov @#CSR+0,R0 ;Fetch word at address CSR+04/CSR+06 Mov @#CSR+2,R0 ;Fetch word as above, auto-increment word address Mov @#CSR+4,R0 ;Fetch low 16 bits of address Mov @#CSR+6,R0 ;Fetch high 16 bits of address Increasing the number of IOPAGE Registers will facilitate access to Byte, Word, Double Word and Quad Word values. Also included will be the ability to Add, Subtract and Multiply (initially only unsigned) 16 bit, 32 bit and 64 bit values. The other set of changes which are exclusively for RT-11 are the enhancement of the HD(X).SYS device driver. Initial tests using HD(X).SYS have provided the confidence that I/O throughput is approximately double that for the MSCP or DU(X).SYS device driver. While the initial version of HD(X).SYS which John has made available supports only 32 MB devices, adding a DU: type translation table will allow support for up to 2 TB devices. It should be possible to modify the simple device drivers for RK05s under RSX-11 and RSTS/E to support the HD: device under E11. However, I can't help with this myself. If anyone is interested, please respond with suggestions and questions. If no one responds, I will proceed to enhance HD(X).SYS and EMEM32 after which I will send any hobby user a copy if requested. If any commercial user of Ersatz-11 is interested, I will first contact John Wilson to be sure that such use is allowed. Sincerely yours, Jerome Fine