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Text File | 1991-01-24 | 18KB | 346 lines

AMIGA (tm) TECHNICAL NOTE 29-Mar-86 Upgrading an AMIGA A1000 with a Motorola MC68010L8 by Thad Floryan For quite awhile now, I've been experimenting using an MC68010L8 in place of the MC68000 in my Amiga. The benefits of the MC68010 are great, but several "problems" with the MC68010 upgrade have held me back from recommending this simple enhancement to everyone. Now, the final quirk has been solved, and I am recommending the upgrade to everyone! This document has several parts, ALL of which must be read and understood by anyone wishing to perform the upgrade or contract for someone to perform the upgrade for you. Additionally, there are several files which accompany this technical note: CHOP.BAS CHOP.C DeciGEL DeciGEL.asm DeciGEL.make The several parts of this document are: I. The MC68010 hardware upgrade II. The MC68010 software upgrade III. Copy of Motorola's MC68000 Micro Minutes MM-444-02, entitled "Advantages of Upgrading an MC68000 to an MC68010". IV. Side notes V. Trademark notices -------------------------------------------------------------------------- ** DISCLAIMER ** The modification and details described in this technical note are provided "as is", without warranty of any kind, either expressed or implied, inclu- ding, but not limited to, the implied warranties of fitness for a particu- lar purpose. The entire risk as to the results and performance of the mo- dification is assumed by you. In no event will I, Thaddeus P. Floryan Jr, be liable for direct, indirect, incidental or consequential damages resul- ting from the use or application of this information. -------------------------------------------------------------------------- I. The MC68010 hardware upgrade The MC68010 is pin-for-pin compatible with the MC68000 installed in all Amiga Model A1000 PCs. The hardware upgrade consists of replacing the MC68000 with the MC68010. ** CAUTION ** The internals of the Amiga are sensitive to static and are fragile; working on a computer is not like working on your car. Also, opening the Amiga will void your warranty. It may be worth your peace of mind to contract an experienced technician for the hardware part of this upgrade. Common sense and a good mechanical aptitude are essential. Take your time and do not rush; restrain your excitement for later, after the MC68010 is installed. To open the Amiga, the five screws on the underside of the case must be removed. Releasing the cover can be tricky; examine the left side of the case near the power switch (front side corner) and also 10 inches further back along the seam and note the tabs: push in until they separate, then lift the cover up toward the right side of the case and release the tabs there. The metal RFI shield covers the entire PC board and must be removed to gain access to the MC68000. Remove all the screws along its edge, and also straighten out the tabs which protrude upwards through the shield, then lift and remove the shield; be sure to note where each screw is supposed to be located as there are several types of screws. The disk drive must also be removed since it sits over one edge of the MC68000. First unplug the two cables (power and signal) after noting the orientation so that they can be replaced correctly later. Now remove all screws fastening the disk drive and lift it up and out: NOTE that the wires to the LED are still fastened; these do not need to be removed if you turn the drive upside down and lay it on a thick book alongside the right side of the Amiga case. Pry the MC68000 out and replace it with a MC68010L8. Reverse all the previous steps to reassemble the Amiga; the tabs which protrude through the RFI shield need not be twisted back into place. Reconnect all the cables to the Amiga. Powerup the Amiga and boot with your usual Kickstart and Workbench disks. Verify that the system appears to be working as normal. Now, either from the Workbench or CLI, startup the CALCULATOR tool, and perform the operation: " 9 * 3 = ". There should be a software failure; this indicates the MC68010 is running correctly because the CALCULATOR supplied with V1.1 uses a "MOVE SR,ea" instruction which is invalid in user-mode with a MC68010. Reboot the Workbench and proceed now to section II, software upgrade. If you do not experience the symptoms as described above, there may be several reasons: 1. you re-installed the MC68000 instead of the MC68010, 2. the MC68010 is "dead", or 3. something else inside the Amiga has been damaged. At this point, you are on your own. My advice is to re-install the MC68000 and verify that your system works again; if it does, then your MC68010 chip may be bad. If your system still does not operate with the MC68000 back in, then you gotta heap of trouble. Re-read the DISCLAIMER above, and seek competent technical service. --------------------------------------------------------------------------- II. The MC68010 software upgrade Beginning with V1.1 of Kickstart and Workbench, Commodore-Amiga "officially" supports operation of the MC68000, MC68010 and MC68020 CPU chips in the Amiga Model A1000 per: "With the exception of the Calculator, software in the 1.1 release is compatible with the 68010 and 68020 processors. Application programmers wishing to take advantage of such products should be sure to use the Exec GetCC() function to get the processor condi- tion codes. (GetCC() handles the differences between the proces- sors such as the fact that "MOVE SR," is an invalid user mode operation in the 68010 and 68020.) In addition, programmers should be sure to NOT use the upper 8 bits of a pointer for storing unrelated information, since the 68020 uses all 32 bits for addressing. = For those doing systems work, Exec maintains flags in the AttnFlags field of ExecBase which describe the type of processor in your machine. Exec's coldstart procedure will update certain library entry vectors as neccessry to maintain compatibility. If you write code that uses the Supervisor() function, keep in mind that your stack frame is processor dependent. Use the SuperState() function for processor independent supervisor mode entry. = V1.1 ROMWack will correctly display information for 68010/68020 address and bus errors. " OK, as you can see, simply by having installed the MC68010, you will be able to use most Amiga system software without any problems. But, the CALCULATOR and other programs loaded with libraries using "MOVE SR,ea" will cause your system to go to lunch with the Guru. This is the reason I haven't encouraged people to upgrade their Amigas until now; only a knowledgeable person would have been able to either live with the occasional problem, or rebuild the software to not use the "MOVE SR,ea" instructions. So what happened all of a sudden to change my mind? Simply that one clever person has developed a short and elegant software solution that prevents the "MOVE SR,ea" instructions from crashing your system. "How," you may ask, "is this done?". It's done by inserting a "wedge" that intercepts instruction privilege violations, examining the offending instruction for the presence of "MOVE SR,ea" and, if found, replacing that instruction in memory with a "MOVE CCR,ea" and resuming at the point of failure. Since the only valid use of the system status register (SR) in a user-mode program would be to get the condition codes, the assumption made by the "wedge" is a reasonable one. And, it works! I've been testing ALL the cases that failed previously with the MC68010 in the Amiga and they ALL perform correctly now. I have included 5 programs with this technical note: CHOP.BAS public domain, author: Anonymous CHOP.C public domain, author: J S Plegge DeciGEL public domain, author: Scott Turner DeciGEL.asm public domain, author: Scott Turner DeciGEL.make public domain, author: Scott Turner DeciGEL is the "wedge" program that needs to be placed in the "c" directory of your workbench disk; DeciGEL.asm is the Assembler source file, and the DeciGEL.make is an EXECUTE file that will recreate DeciGEL from DeciGEL.asm. If you don't have the Amiga Assembler, you can simply download DeciGEL and use it immediately. It is best to include a line in "s/startup-sequence" on your Workbench disk that will call DeciGEL. For example: echo "Workbench disk. Release 1.1" echo " " echo "Use Preferences tool to set date" echo " " DeciGEL . . The CHOP.BAS and CHOP.C programs are used if you download DeciGEL and use the progam directly, without rebuilding. The CHOP programs must be used to make SURE the DeciGEL program is exactly 168 bytes long. You can determine the size of DeciGEL on your system by using the CLI's LIST program. If the size is greater than 168 bytes, CHOP will allow you to truncate (or chop) the file to 168 bytes. CHOP.BAS operates with ABasiC (not AmigaBASIC), and CHOP.C is the source of a "C" program; use either one as appropriate for your needs. With the MC68010 installed and DeciGEL "wedged", your Amiga should operate anywheres from 4% to 50% faster depending on what you're doing. Note that the "Boing!" demo will not be faster since its timing is synchronized to the vertical framing of the monitor's clocking which is FIXED per NTSC TV standards! The biggest benefits of the MC68010 upgrade will occur with heavy number-crunching applications, such as spread sheets and Mandelbrot picture generations. Enjoy! -------------------------------------------------------------------------- III. M68000 MICRO MINUTES (c) Motorola MM-444-02 Advantages of Upgrading an MC68000 to an MC68010 There are several ways a system's performance can be upgraded. Some are software related, such as lowering operating system overhead, obtaining better quality language compilers, wisely designing application programs, and coding applications more efficiently. Others are hardware related, such as adding memory, improving I/O channel data rates, increasing mass storage speed and capacity, reducing memory access times, and upgrading the system processor's clock frequency. When considering an MC68000 system upgrade to higher performance, the obvious thought is to redesign for a higher frequency MC68000. For example, a current MC68000 system running at 10 MHz could be redesigned to run at 12.5 MHz, thereby increasing system throughput by 25%. The "obvious solu- tion", however, is not necessarily the most appropriate or cost-effective once several factors are taken into consideration and alternative solutions examined. The speed-up of a system clock will not be effective unless the system's memory access time is also improved. The performance of the MC68000 is strictly limited by the bus speed, and if no improvement in memory speeds are available, then an increase in system clock speed will lead to negligible improvement in the overall result. A 10 MHz processor running with no "wait states" utilizes a 400 nS bus cycle (4 clocks x 100 nS/clock). This same bus cycle timing, however, leads to a wait cycle on a 12.5 MHz processor (4 clocks x 80 nS/clock + 80 nS of idle time). Thus, the bus performance is exactly the same, but the faster processor is idled for one complete clock cycle. Since a decrease in the bus cycle time provides a directly proportional increase in processor throughput (until, of course, the memory cycle becomes faster than the fastest processor bus cycle), the 12.5 MHz processor has no relative performance advantage over the 10 MHz system. The bottom line, then, is that in order to be effective, a higher speed processor must run with fewer or the same number of "wait states". This normally requires a redesign of the memory subsystem to improve the memory access time. Referring to the MC68000 Data Manual (ADI-814-R4), the memory access re- quirements for the various speed processors can be examined. The effective memory access time (Taccs) of the MC68000 to a memory array (from assertion of Address Strobe [-AS] to data valid) is: Taccs = Tch + 2Tcyc - Tchs1 - Tdic1 + (n * Tcyc) where: Tch is the clock high time (system dependent) Tcyc is the clock period of the processor clock Tchs1 is the delay time from the rising edge of the clock to the assertion of address strobe Tdic1 is the data input set-up time prior to the falling edge of the clock n is the number of wait cycles in the system Assuming a symmetric clock (50% duty cycle), the memory speed required for a no "wait-state" bus cycle for a 19 Mhz MC68000 processor is 185 nS (50 + 200 - 55 -10 + 0). This bus speed can be easily realized with readily available 150 nS dynamic RAMs and careful system design. However, with the same assumptions, the memory speed required for a no "wait-state" bus cycle on a 12.5 Mhz processor is reduced to 135 nS (40 + 160 - 55 - 10 + 0) which presents an obvious problem to the cost-conscious system designer -- lack of cost-effective, large capacity 100 nS RAMs! Memory access times are not the only difficulty encountered with the faster clock speeds. In a similar vein, the design of an efficient 12.5 MHz system is more difficult than that of a 10 MHz system, since more careful attention must be paid to the physical design of the board in order to account for the higher frequency signals present, and the increased sensitivity to transient phenomena. A "painless" alternative means to EFFECTIVELY increase system performance is to upgrade to the MC68010 processor. The MC68010 at equal clock fre- quencies will run from 8% to 50% faster than an MC68000 without any user code changes. The speed-ups are due to several microcode enhancements: many 32-bit operations, conditional branches, multiply, divide and other miscellaneous instructions run faster. Systems which use memory management can have dramatic improvements with slight operating system changes utilizing a few new MC68010 instructions such as "Move to/from Address Space" (MOVES). Systems may see a significant improvement if they heavily utilize multiply, divide and looping operations. Loops run from 23% to 80% faster once the microcode sets up the automatic "loop mode". Such loops benefit particular functions such as block moves, character matching and general string manipulation operations, and multiple-precision binary and packed BCD arithmetic. The new MC68010 multiply is 14 clocks faster, and the divide is 32 clocks faster than the MC68000. Programs utilizing (or with the potential of utilizing) such operations can obtain an increase in perfor- mance easily exceeding 10%. An additional "plus" of the MC68010 is the provision of a clear path for the upgrade of current operating systems to full virtual operating systems utilizing the sophisticated virtual memory processing capabilities of the MC68010 (which is the same virtual environment offered by the 32-bit MC68020). Since the MC68010 is pin-for-pin compatible with the MC68000, *NO* hardware redesign is necessary. Only very minor software changes may have to be made depending on operating system conventions. The MC68010 differs from the MC68000 in that: 1) a generic "vector word" has been added to the MC68010 stack frame; and 2) the MC68000's "MOVE SR,ea" has been made a privileged operation. Easy software solutions for these two minor differences are: 1) any routines which build exception stacks (e.g. those which dispatch a routine via an RTE instruction) are modified to account for the four word stack frame (the MC68000 uses a three word stack frame); and 2) an exception handler is added to provide for privilege violations generated by the execution of the "MOVE SR,ea" instructions in the USER state (local Motorola representatives can supply a debugged handler to suit the requirements of any OS). Major operating systems have been ported from the MC68000 to the MC68010 in less than a single day, reflecting the trivial changes required in the super- visory level code. The bottom line is, by upgrading an MC68000 system to an MC68010 system, an increase in system performance is obtained which is equal to that which a system redesign from 10 MHz to 12.5 MHz would provide, but with signifi- cantly less design cost and effort. The "speed-only" upgrade could only achieve, at best, a 25% system improvement, and only if the system memory access time is significantly improved. The MC68010 upgrade offers from 8% to 50% improvement. Note that the speed gained by changing to the MC68010 is achieved with NO change in memory speeds, NO board redesign, and NO higher speed parts installed in the system as would be required to upgrade a system to a 12.5 MHz part. --------------------------------------------------------------------------- SIDE NOTES: (1) Commodore-Amiga has provided for the four word stack frame in Exec. (2) the DeciGEL program is the privilege violation exception handler. --------------------------------------------------------------------------- Amiga is a registered trademark of Commodore Business Machines, Inc.