Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!blkcat!Uucp From: Charlie.Mingo.Of.30039/4218@f421.n109.z1.FidoNet.Org (Charlie Mingo Of 30039/4218) Newsgroups: comp.sys.mac.hardware Subject: Re: 68040 for 68030 substitution (question) Message-ID: <676764015.1@blkcat.FidoNet> Date: 12 Jun 91 18:59:28 GMT Lines: 161 In article alanr@cecelia.media-lab.media.mit.edu (Alan Ruttenberg) writes: > I was wondering if a 68040 can be substituted for a 68030 in a > MacIIfx. I understand that the pinouts and the clock rate (40Mhz 030 > 25Mhz 040) are different. > > What I am curious about is what a minimal upgrade to a 040 would > entail. Can I buy a chip, and build a small adapter board? Or are > there many changes that would have to be made. To give you an idea of the problems involved, I'm attaching a memo downloaded from CompuServe, which outlines why DayStar won't be offering a 68040 accelerator until *after* Apple ships its own version, and patches the OS to support the 040. Note that I am only relaying this information, and am not offering it as my own views (although it looks persuasive). Comments, questions and (especially) flames should be directed to "73777.2453@compuserve.com"; I will ignore any flames sent to me. ----------------------------------------------------------------------------- The 68040 on the Macintosh [Originally from: Steve Tuttle [DayStar] 73777,2453 From Internet --> 73777.2453@compuserve.com Reposted without permission] March 25, 1991 (c) DayStar Digital, Inc. 1.0 Overview The Motorola 68040 processor is a major step forward in processing power. When compared to a 25 MHz 68030/68882, a 25 MHz 68040 offers double the integer performance and three times the speed in floating point calculations, as shown in Table 1. But a 25 MHz 68040 is only slightly faster than a 40 MHz 68030 (Mac IIfx). Table 1 Performance Relative to a 25 MHz 68030/68882 Ref: Motorola Type 25 MHz 68030 40 MHz 68030 25 MHz 68040 -------------------------------------------------------------- Integer 1.0 1.6 2.1 FPU 1.0 1.6 3.3 Integer calculations, which drive Mac operating system (OS) performance and all applications show gains of 30%. The real strength of the 68040 lies in the speed of floating point calculations, but these have little or no benefit for the typical graphics user. Only applications in the scientific and CAD markets use the floating point unit (FPU). In several years the 68040 will be running at 40 MHz. This processor will provide the much needed power in the DTP, graphics, pre-press and scientific markets. Software compatibility will be a major problem on 68040 accelerators as well as Apple's new 68040 machine. Apple will have to make major patches to the Mac OS to handle problems with memory management and exception handling. In addition, the math code within applications will have to be rewritten to directly leverage the benefits of the 68040's FPU. For these reasons, DayStar has decided to wait to introduce its 68040 accelerator until after the introduction of Apple's 68040 machine. Apple is best suited make the necessary OS changes as well as drive changes in third party applications, INITs and cdevs. 2.0 Lessons From the Past Each new generation of processor from Motorola has incorporated new features and capabilities, many of which are not compatible with the current generation. The Mac OS, by its very nature, directly addresses the hardware. To the extent that the hardware changes, the OS must be patched. The greater the change in the architecture of the processor, the greater the number and sophistication of the patches. 2.1 The First Accelerators The first Mac Plus and SE accelerators utilized a 68020 with a 32-bit bus as compared the 16-bit bus on the Mac SE's 68000 processor. That and its faster clock speed (16 MHz vs. 8 MHz) caused many aggravating incompatibilities with parts of the Mac OS, various applications, and many INITs. It was not until the Mac II was introduced with its own 16 MHz 68020 did Apple and the developer community completely solve the problems. 2.2 The Mac II Accelerators Problems started over again when Apple introduced the 16 MHz 68030 Mac IIx. Surprisingly, the 68030 is nearly identical to the 68020 except for the addition of the 256 byte internal data cache and the memory management unit (MMU). Yet there were numerous incompatibilities with various parts of the Mac OS, third party INITs and applications. Many cdevs and INITs accomplish their special task by making changes to the OS or directly addressing the hardware (necessary to accomplish a special task that Apple did not provide, nevertheless, a violation of Apple guidelines). Applications that closely followed developer guidelines generally worked well on the 68030 conversion. There were several key applications that had problems working with the internal cache. At the same time DayStar introduced its 33 MHz 68030 accelerators. Once again, it (and others) exposed yet another set of problems with applications, INITs and cdevs that had clock timing dependencies and problems working with an external memory cache. Even Apple's floppy driver code would not run properly at speeds above 16 MHz. DayStar (and others) invested significant time patching the floppy driver code. For the 25 MHz Mac IIci, Apple had to completely rewrite their floppy driver code to eliminate these timing dependencies. From a software standpoint, conversion from the 68020 world to the 68030 was about as easy as one could ever ask for. Yet it was very frustrating for the end-user. While most problems were encountered with INITs and cdevs, users were not willing to eliminate them as they had become an essential part of their "tool kit". Some early buyers found the experience very frustrating - they did not have the time (or skills) to fiddle around trying to debug their machine. The same experience was once again repeated when Apple introduced their 32-bit clean ROMs on the Mac IIci and Mac IIfx. With over a year of warning from Apple to the developer community, there were still many applications, INITs and cdevs that had significant problems, driving the users crazy. 3.0 Performance The 68040 incorporates several innovative design features that boost performance over a 68030/68882 combination running at the same clock speed. Gains are realized in both integer and FPU performance. Integer performance drives the Mac OS and virtually all applications. Mac OS, graphics, DTP and pre-press applications make little or no use of the FPU, as shown in Table 2. FPU performance is of benefit only for a subset of functions within CAD and scientific applications. Spreadsheets only use the FPU for spreadsheet recalculations. Table 2 Benefit of 50 MHz FPU on IIci Accelerator Ref: DayStar Platform Mac IIci Accel IIci Accel IIci Accel IIci Processor 68030 68030 68030 FPU Clock 25 MHz 50 MHz 50 MHz % Gain FPU Yes No Yes Yes ----------------------------------------------------------------------- Word Scroll 8.9 6.5 6.5 0% RenderMan Render 98.0 82.0 56.0 46% Excel Cut&Paste 9.1 5.5 5.5 0% Excel Scroll 10.3 10.0 0.0 0% Excel Recalc. 10.4 6.6 5.6 17% Quark Xprs Fit in wind 5.4 3.4 3.4 0% Quark Xprs Scroll 24.2 16.9 16.9 0% FreeHand Fit wind 21.8 11.9 11.9 0% FreeHand Duplicate 34.5 18.7 18.7 0% FleMkr Pro Sort 56.3 42.2 42.2 0% Swivel 3D Change View 17.4 8.1 8.1 0% Swivel 3D Tween 73.1 32.6 32.6 0% Claris Cad Fit in wind 6.5 4.6 4.2 8% Photo Shop Rotate 4.8 3.6 3.6 0% Photo Shop Resample 36.6 19.7 19.7 0% Photo Shop Gausian Blr 19.3 12.0 12.0 0% --------------------------------------------------------------------- Total Time (sec) 436.53 284.18 256.79 11% Shown in Table 2 is a Mac IIci accelerator with and without a 50 MHz 68882 FPU. Doubling the speed of the FPU has no benefit in many applications, even within CAD applications. Based on the evidence in * Origin: The Clone: Macintosh Things - 301-946-8677 (1:109/421)