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chiaki

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  1. micron produced actually 1Mx4 DRAM ICs without JEDEC testmode implemented. like mt4c4005 and "newer" produced DRAM also dont have the jedec testmode in the datasheet also found a detail description about the difference in the datasheet, maybe it help
  2. chiaki

    Dumb*]#* eBay sellers

    even apple doc say "remove screw if one present", are they even new shipped without?
  3. chiaki

    Dumb*]#* eBay sellers

    maybe the seller dont know how fragile old plastic is, looks like even the only screw on the LC missing too
  4. The IIcx (and SE30 too?) looks very similiar to the IIx schematics and have an PAL which control the Bank A/B RW-Line. Maybe its possible to modify the IIx with an custom logicarray to do the same.
  5. (relevant information from Apple Developer Technical Support April 1992 Document) 4 Mbit DRAMs in Revolt When the Macintosh II was originally designed, Apple engineers intended for it to accept large amounts of memory in the form of 4 MB and 16 MB DRAM SIMMs. That was in 1986, when 1 Mbit DRAM was difficult to find and the higher-density chips did not yet exist. The engineers anticipated the pinouts of the yet to be introduced 4 MB SIMMs and provided all the necessary hardware and address multiplexing to allow installation of these parts when they became available. Woe that Cupertino is not Camelot, James Brown is still on probation, and 4 MB SIMMs do not work as advertised in most cases. This is the story of the Revolt of the 4 MB DRAM SIMMs. Preliminary Notes Before diving into the problem with 4 Mbit DRAMs, there is some preliminary ground that must be covered. First, there are a couple ways to construct a 4 MB SIMM. Using old technology, it is possible to cram together 32 DRAM ICs of 1M x 1 density. Using new technology, it only takes eight 4M x 1 ICs, resulting in a much smaller, lower-power module. If a 4 MB SIMM is of the large, so-called composite type (that is, it is constructed of 32 1 Mbit ICs), then everything is fine except on the original Macintosh II. Please refer to page 7 of this Tech Note for more information on Macintosh II RAM. With the FDHD SuperDrive upgrade kit installed, the Macintosh II is on equal footing with the Macintosh IIx. That is, SIMMs made exclusively of the new 4 Mbit ICs still won’t work, regardless of whether you are using a Macintosh II or IIx; therefore, for the remainder of this discussion, Macintosh II is used to refer to not only the original Macintosh II, but also the IIx. Subsequent Macintosh models have revised ROMs that recognize 4 MB SIMMs. The 4 Mbit Problem DRAM ICs are now available in 4 Mbit density, but they come with a very nasty surprise. JEDEC, the committee overseeing the standardization of new solid-state devices, has added an additional built-in test mode to high-density DRAMs. The test mode is invoked by a sequence of electrical signals that was ignored by earlier-generation DRAM. The crux of the situation is this: under certain conditions, the Macintosh II unwittingly activates this new test mode and large amounts of memory become very forgetful. More Specifically . . . Those who are interested in the specific phenomenon occurring within the memory ICs should consult the detailed technical data supplied by the DRAM manufacturers. This Note only explains how the Macintosh II offends this new feature of the 4 Mbit DRAM, and hence, what might be done to work around the problem. The Macintosh II uses /CAS-before-/RAS refresh cycles to keep RAM up to date on its contents. For 1 Mbit DRAM, the state of the /W control line is ignored during this type of refresh cycle. No longer. DRAM of the 4 Mbit variety goes off into test mode if /W is asserted (low, so that the RAM thinks it is write-enabled) during a /CAS-before-/RAS refresh cycle. The problem with the Macintosh II is that /W is the same signal as the MPU R/W line, and if the MPU is writing to an I/O address or a NuBus™ card concurrently with a refresh cycle, all the conditions are right for a waltz into test mode. Unfortunately, this condition is not all that unusual, since video card accesses qualify Consolation for SIMM manufacturers: SIMMs constructed with an on-board PAL are not necessarily Macintosh II-specific. SIMMs constructed in this manner should work without modification in any usage calling for 4 MB SIMMs (except in the unlikely event that the new test mode is required). The Salvage Process All is not necessarily lost, and although the situation is ugly, there is still a way to use 4 Mbit DRAM ICs to construct 4 MB SIMMs that work in the Macintosh II. A solution lies in the addition of a ninth IC to the SIMM. Programmed with suitable logic, a high-speed (-D or -E suffix) PAL on the SIMM itself can recognize and intercept /CAS-before-/RAS refresh cycles and set /W appropriately before any damage is done. More or less, the PAL becomes an intelligent buffer between the MPU read/write line and the DRAM write-enable lines. When the PAL senses a refresh cycle commencing, it holds /W high, ensuring that the ICs are not corrupted by the potentially dangerous processor-generated R/W signal. What’s the Point? You have overcome all the problems discussed in this section and have working 4 Mbit SIMMs installed in your Macintosh. You probably have at least 20 MB of RAM. What can you do with all of it? Create lots of huge 32-bit PICTs and edit them all simultaneously? Model and animate Bay Area weather patterns in Mathematica™? Yes! But, you have to use the appropriate system software to address this memory. Also, if you’re running in 32-bit addressing mode, the applications that you desire to use need to be 32-bit clean. For more information on 32-bit cleanliness and addressing, please see Technical Notes #212 and #213. Under System 7.0, applications can finally access additional physical memory over and above 8 MB. As mentioned previously in this Tech Note, the 32-bit addressing mode of System 7 requires either a Macintosh with 32-bit clean ROMs (listing is on page 2), or else the 32-bit software solution provided by the MODE32 system extension. A/UX is an alternative that can use up to 256K of RAM on Macintosh computers that support A/UX. Many manufacturers of large SIMMs also offer RAM disks. This is a volatile form of storage, but can certainly be useful for I/O intensive operations. Other Permutations The problem with 4 Mbit DRAM is not limited to 4 MB SIMMs. It is the 4 Mbit density of the individual RAM ICs that causes problems with certain machines. There exist 1 MB SIMMs constructed of only two 1M x 4 (4 Mbit) ICs. These do not work in a Macintosh II or IIx, any more than 4 MB SIMMs constructed of eight 4M x 1 ICs. A few machines, namely the Macintosh Plus, Macintosh SE, and Macintosh Classic, depend on video accesses to refresh all of their DRAM. As the video circuitry accesses sequential locations through the video frame buffer, it simultaneously refreshes row after row of memory, eventually refreshing all 512 rows. Memory at the 4 Mbit density, however, is arranged as 1024 rows and there are not sufficient video accesses to refresh all 1024 rows. Chunks of memory simply go blank. Thus for a different reason, 4 Mbit DRAM parts are also not compatible with these older Macintosh hardware designs. Executive Summary Owners of the Macintosh Plus, SE, Classic, II, or IIx are all likely to have problems with any 1MB SIMM carrying only two ICs, or any 4 MB SIMM carrying only 8 ICs. Any SIMM constructed in one of these ways likely uses 4 Mbit density DRAM ICs and does not account for problems with the 4 Mbit test mode nor the video refresh strategy of older Macintosh designs.
  6. im still try to figure out what exactly those special PAL memory do, i found only this information: also i figured out my IIx does not work with 1MB SIMM with three ICs (2x 1Mx4 + 1x 1Mx1 for Parity) Only with eight/nine (e.g. 1Mx1 DRAM)
  7. have a Quantum GO16S021 Rev 02-H (with apple firmware from 1992?) in my powerbook 165 which worked some time ago sometimes and now is completely death (not even attempt to spin up). after read out the rom (socketed PLCC) its just garbage. maybe anyone can help me with a romdump? the sticker of version is E2860, but maybe it not must be the same version.
  8. I got a Powerbook 165 but without power supply I tried 9V 1A and it works little bit, but its not reliable (floppy access goes into a reboot). Have anyone tried a 12V (2A) power supply?
  9. I got a Powerbook 520 with 4MB Memorycard, but 8MB Memory is not enough for me I attached pictures from the card, has anybody a clue what memory and what resistor i must solder?
  10. My Quadra 840av dont boot from any SCSI-Devices at boot. When i boot the Mac OS 7.5 floppy, the apple drive setup tool say that the harddisk doesnt contain any valid partitions, and it cant format it. I test it on the internal and external SCSI-Bus, with ZIP100 and my 2Gb Harddisk from the Quadra 700 (my Quadra 700 can read and boot from the DIsk)
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