ProfitPress Mega CDROM2 Shareware Freeware (MSDOS)(1992)(Eng)

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Text File | 1991-04-12 | 10.9 KB | 225 lines

┌─────────────────────────────────────────────────────────────┐ │ Trademarked names are the property of the respective owners │ └─────────────────────────────────────────────────────────────┘ (c) Copyright 1991 F.M. de Monasterio Licensed Material - All rights reserved TIMEM version 1.00 ------------------ 1. SUMMARY TIMEM is a utility to measure memory access times over a range of memory as small as 1 kb or as large as 1 Mb. It is useful for the selection of an upper-memory block (UMB) for resident utilities capable of installing themselves in upper memory (via an XMS manager) and of selecting a lower limit for the UMB. ----------------- 2. GENERAL INFORMATION Several types of addressable memory are found in iAPX 80x86 CPUs. In all DOS-compatible machines, however, the first megabyte (1 Mb = 1,024 kb) of memory comprises the initial 640 kb of address space used by DOS, and the remaining 384 kb of address space used by hardware subsystems and by BIOS routines. The addressable megabyte is referred to as conventional memory and its 384-kb subspace as upper memory blocks (UMBs) or high-DOS memory. 0 kb 640 kb 1024 kb DOS UMB ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓ In the IBM AT and compatibles, which can support a physical address space larger than 1,024 kb, additional memory is located above the initial 1 Mb of space, up to a physical address space of 16 Mb in i286 and i386SX CPUs and 4 Gb in i386 CPUs. The additional addressable RAM is called extended memory and is subdivided into a high memory area, which is the initial 64 kb area immediately above the 1-Mb limit, i.e. from 1,024 kb to 1,088 kb, and the extended memory blocks (EMBs), located above the physical address at 1,088 kb. 1Mb 16Mb-4Gb Extended memory ▒▒▓░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ 0 kb Irrespective of the CPU, DOS runs in an 086-compatible mode known as real mode. In such a mode, where addressable memory is seen as consisting of a series of 64-kb segments, memory addresses are made up of two portions: a 16-bit SEGMENT, between 0 and 65,535 (or FFFFh in hexadecimal), and a 16- bit OFFSET, which is the distance in bytes (between 0 and FFFFh) from the address to the first byte of the segment. By changing segment:offset values, up to 1 Mb of memory can be addressed; given the inherent overlap of such a method of addressing, it is possible to point to a given locale in memory, such as the beginning of the second kilobyte of the UMB space (641 kb) by more than one segment:offset value, e.g. A400:0000h, A000:0400h, 9FFF:0410h, 9400:C400h, etc. This ambiguity can be resolved by using physical addresses, in which these two parts are combined to form a 20-bit address by multiplying the segment by 16 and by adding the offset to it. (The highest possible 20-bit number is 1,024 kb, which is why this is the maximum space of [086] conventional memory.) ----------------- 3. PROGRAM INFORMATION TIMEM measures access time to a range of conventional memory blocks, each of 1 kb length, starting at a user-specified, zero-offset segment between 0 and FFFFh, and ending at higher zero-offset segment either specified by the user or set automatically by the program. TIMEM is useful to measure access time in sufficient detail to select the best UMB base segment in which to install those resident programs capable of loading themselves into an upper memory block (UMB) via an XMS manager and of selecting a lower high-memory limit for the UMB segment. --------- Because of intrinsic variations, timings should be repeated several times to obtain a more representative evaluation. The results represent micro- seconds per kilobyte (µs/kb) for the particular metric used in this test, and are sent to the video display via DOS. This output can be redirected to a file or the printer through the DOS redirection command > or >> when executing the program. TIMEM uses the microcomputer's timer chip for these measurements. The IBM PC family uses an 8253 (or 8254) timer chip to tally system clock pulses, and for DMA memory-refresh operations, and speaker output. Access timing measurements do not affect the memory contents, but (because of the timer reprogramming) may introduce small inaccuracies in the system-clock pulse count maintained by the BIOS and used by DOS. These inaccuracies are not permanent and disappear when the CPU is rebooted; their occurrence can be minimized by synchronizing timing loops with the system clock pulses (see switch S below), although this results in a penalty in speed performance. TIMEM assumes the system timer is an 8253-compatible chip. If this is not the case (as in IBM PS/2s), switch P helps to avoid measurement errors in computers not compatible with the IBM PC hardware standard. ----------------- 4. USAGE TIMEM [seg1[seg2]] [/switches] [;comments] seg1 The starting zero-offset segment in 4-digit hexadecimal notation ranging between 0 and FFFF. Default: Null argument = A000. seg2 The final zero-offset segment in 4-digit hexadecimal notation of memory range to be timed. The final segment must be higher than the initial one. Default: Null argument = (seg1+15 kb), invalid argument = FFFF. SWITCHES The switches are not case sensitive, may be given in any order, and must be preceded by any ASCII character between space ( ) and slash (/): /N NonStop listing of access timing data. Use this switch when the data will be send to a file via DOS redirection commands. /P Do not assume timer is an 8253-compatible chip (e.g., IBM PS/2). This switch may introduce a small error when timing a very large range of memory in a very slow CPU. /S Synchronize timing loops and the system clock pulses to decrease the possibility of introducing inaccuracies in the time count of DOS when timing a large memory range in a slow CPU. (Such small inaccuracies are temporary and disappear upon rebooting.) Since the clock pulses only every 55 ms, this switch slows down TIMEM. COMMENTS Comments may be added in the command line invoking the program after the desired switches. The comments, which may be useful in clarifying batch files, must be preceded by a semicolon (;), and are ignored by TIMEM. NOTE: Do not use DOS redirection (<>) and pipe (|) command characters in these comments since DOS will try to implement the implied redirection or pipe request. ------------------------------------------------------------------------------ REGISTRATION These programs and the documentations (the "Software") are the copyrighted property of FM de Monasterio (the "author"), who provides the Software and licenses its use. All rights are reserved. The Software is part of a user-supported, shareware package. If you do not wish to register the Software package, but would like to use this utility, please send to the address below a US$5.00 check marked "For Deposit Only" and payable to "PATIENT CARE FUND, CHILDREN'S HOSPITAL" of Washington, DC. Users who donate to such a fund may legally keep and use the utility under the limitations described below. FM de Monasterio P.O. Box 219 Cabin John, MD 20818-0219 DISTRIBUTION You may distribute this Software via magnetic and/or electronic means, but you are specifically prohibited from: - Charging fees or asking donations in exchange of or payment for copies of the Software. - Distributing this Software with commercial products without the written permission from the author. - Distributing this Software via a for-profit organization or group, either alone or with other Software. The unauthorized copying, decompiling or disassembling of this Software is prohibited; any other use of this Software is prohibited without a written permission in advance from the author. WARRANTY DISCLAIMER The author cannot and does not warrant that any function contained in the programs will meet your requirements, or that the operation will be error free. The entire risk as to the Software performance or quality, or both, is solely with the user and not the author. You assume responsibility for the selection of the program to achieve your intended results and for the installation, use, and results obtained from the Software. The author makes no warranty, either implied or expressed, including with- out limitation any warranty with respect to this Software documented here, its quality, performance, or fitness for a particular purpose. In no event shall the author be liable to you for damages, whether direct or indirect, incidental, special, or consequential arising out the use of or any defect in the Software, even if the author has been advised of the possibility of such damages, or for any claim by any other party. All other warranties of any kind, either express or implied,including but not limited to the implied warranties of merchantability and fitness for for as a particular purpose, are expressly excluded. LIMITATION OF REMEDIES The author's entire liability, and your exclusive remedy shall be: (1) the replacement of an original Software diskette not meeting the above Limited Warranty and which is returned to the author along with proof of purchase, or (2), if the author is unable to deliver a replacement diskette which is free of defects, you may terminate the License Agreement by returning this Software and the corresponding license fee will be returned. By using the Software, you acknowledge (1) to have read and understood all parts of this document and (2) to have agreed with and accepted all of its provisions without any reservation. -------------------------------------------------------------------------------- [END]