Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!mailrus!iuvax!bsu-cs!mithomas From: mithomas@bsu-cs.bsu.edu (Michael Thomas Niehaus) Newsgroups: comp.sys.amiga Subject: Re: Commodore, Amiga, Apple, and MAC Message-ID: <10998@bsu-cs.bsu.edu> Date: 29 Mar 90 02:18:05 GMT References: <15003@snow-white.udel.EDU> <10363@cbmvax.commodore.com> Reply-To: mithomas@bsu-cs.UUCP (Michael Thomas Niehaus) Organization: CS Dept, Ball St U, Muncie, Indiana Lines: 108 > Actually, a normal, every-day 32k external cache has more to do with the Mac > MacIIx going fast than anything else. What Apple terms "custom chips" are > smiple gate arrays. They are, for instance, doing some kind of DMA transfer > for hard disk I/O, rather than the 8 bit programmed I/O they've used in the > past. Pretty much what we've been doing all along. While most of the > Mac IIfx does go faster than the 7.16MHz of the A2000, everything > I've seen so far indicates only the cache > is running a real 40MHz 68030 cycle. Here's some real info from the Apple spec sheets. My commentary is added in brackets: % 40Mhz 68030 microprocessor and 68882 floating-point coprocessor. The Macintosh IIfx runs up to 100 percent faster than the Macintosh IIci, and up to 300 percent faster than the Macintosh IIcx and Macintosh IIx computers. [ This processor runs most of the time at zero wait states by using the cache in conjunction with the 80ns memory. This memory is also specially designed to allow burst access, and simultaneous reads and writes, creating an additional performance boost. ] % Built-in 32K static RAM (SRAM) cache stores the processor's most frequently used instructions. [ This is required. Otherwise you would need somewhere in the neighborhood of 40ns memory to get 0 wait states out of the machine. ] % dedicated SCSI DMA (Small Computer Systems Interface/Direct Memory Access) channel which reduces the workload of the main processor and speeds performance of the SCSI bus. [ Actually, there is nothing special about this chip. It is a standard controller. It does effectively double the speed of SCSI on the Macs. Also, with the IIfx, this is the first time that DMA was supported by the operating system. ] % dedicated I/O processors increase system efficiency. [ These I/O processors are really 6502 processors, the same as used in the old Apple II line of computers. They handle the floppy drive, Apple Desktop Bus (mouse and keyboard), and serial ports (which includes Apple's LocalTalk networking). This takes quite a load off the CPU as well. ] % six NuBus expansion slots can Accommodate multiple video, communications, networking, and other expansion cards. [ Same as all of the other Mac II models. No changes in speed or capabilities. ] % Processor Direct Slot (PDS) allows direct access to the system bus. [ This is new to the 6-slot machine as well. It gives the possibility of adding cards that run at a much higher speed than NuBus. I'm sure that someone will think of a good application for this. ] % six built-in ports: two serial ports, two Apple Desktop Bus ports, stereo sound jack, and a DB-25 SCSI interface. [ No change here either. ] % 512K ROM on SIMM includes support for 32-bit QuickDraw and A/UX-supported functions such as: 32-bit addressing and virtual memory, which extends the computer's internal memory by transparently treating the hard disk as though it were RAM. [ Same as the IIci. ] Here is some more information from the Apple releases. All marketing mumbo-jumbo has been removed wherever possible. Q: How many new Application Specific Integrated Chips (ASICs) are on the Macintosh IIfx board? A: There are a total of seven new ASICs. Two are Peripheral Interface Control (PIC) Chips, which are dedicated to controlling low-level routines such as serial communication and floppy disk access. There is one Small Computer System Interface/Direct Memory Access (SCSI/DMA) chip, which controls the SCSI bus. There is one Operating System Support chip, which is a multipurpose ASIC, dedicated to managing interrupts from external sources so they are synchronized with the internal bus. There is one Bus Interface Unit 30 chip and a Bus Interface Unit 2 chip, which drive NuBus processes and bus synchronization, respectively. There is one Faster Memory Controller chip, which controls access from the cache, ROM, and RAM to the system's main processor. Additionally, there are four ASICs which also appeared in the Macintosh IIci design. Q: What sort of advantages does the Macintosh IIfx get from the Peripheral Interface Control (PIC) chips? A: The PIC chips are important to the overall performance of the Macintosh IIfx system, as they balance the increase in clockspeed to 40 MHz by ensuring that I/O processes keep pace with the processor's speed. Additionally, they free the main processor from processing low-level interrupts. As a result, the PIC chips provide high levels of dedicated and predictable performance for standard I/O routines. For example, network routing techniques on the Macintosh IIfx are completely transparent to users performing any number of Macintosh applications. In future versions of the Macintosh operating system, the Macintosh IIfx will take greater advantage of the PIC chips' capabilities. That should give you enough information to dwell on for a while. -Michael -- Michael Niehaus UUCP: !{iuvax,pur-ee}!bsu-cs!mithomas Apple Student Rep ARPA: mithomas@bsu-cs.bsu.edu Ball State University AppleLink: ST0374 (from UUCP: st0374@applelink.apple.com)