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  1. mdeverhart

    Major Score! 8600 with Sonnet CPU, 3DFX card, Etc

    According to this, you need 5V DIMMS (not 3.3V), so be careful: https://www.macgurus.com/products/motherboards/mbppc8600.php -- This computer requires either 5-volt, 64-bit, 168-pin fast-paged mode (FPM) 70ns DIMMs, in 2k or 4k refresh, or 5-volt, 64-bit, 168-pin Extended Data Out (EDO) 60ns DIMMs. As these machines typically ship with 32MB EDO DRAM (either a single 32MB DIMM in slot B4 or a pair of 16MB DIMMs in slots A4 & B4), MacGurus recommends the installation of EDO memory, despite the fact that no performance benefit accrues through its use. Note: MacGurus reccomends the use of 168-pin, 5v EDO 64-bit, 2k refresh, 60ns DIMMs in this machine. EDO DIMMs are engineered to higher tolerances, and are more compatible with G3 processor upgrades. The two types of RAM can be mixed in a machine. --
  2. mdeverhart

    Bringing my Apple Centris Back to life

    Assuming it doesn’t have a PPC upgrade card, it’ll need a startup disk with the 040 System Enabler if you’re using System 7.1. The System 7.5.3 installer disks are widely available and should boot without issue. My recollection is that you can boot from the CDROM drive if it’s one of Apple’s (either factory original or another compatible Apple OEM drive). Yes, the flashing ‘?’ disk means it can’t find a valid System Folder. Either the HD has died or the system has gotten corrupted somehow. I’m not sure why your original install disks are giving you that message. Is there a Disk Tools disk with your set, or a disk labeled “Install Me First” or something like that? You might need to boot from one of those, then eject that disk and proceed with installing from the other disks. The Disk Tools disk will also have the hard drive setup utilities that might be useful for checking out the HD. The main modern option, if the HD is dead, is the SCSI2SD. It uses a SD card and emulates a SCSI HD. There’s plenty of information on this site and on the web about setting one up for a vintage Mac. There are other options (using a U320 SCA SCSI with an adapter), but it seems like most folks go the SCSI2SD route.
  3. Happy to help @lowlytech. No need to feel silly, these systems are old and it can be hard to find good documentation online for them. I only remember from a LOT of time on System 7 machines back when they were new(-ish).
  4. My recollection is that system enablers are just dropped into the top level of the System Folder (where the Finder and System suitcase are).
  5. mdeverhart

    50 pin -> 80 pin SCSI?

    There was a brief discussion on another thread recently:
  6. mdeverhart

    SE/30 DiiMO accelerator cloning

    Thanks. I didn’t realize the forum SW allowed for arbitrary file attachments. I haven’t gotten to thinking about the clock buffering/shifts yet. Good times!
  7. mdeverhart

    Performa 476 Restoration

    I suppose it depends on if you want to use it for anything in particular, or if you just want to have a System 8.1 machine. I had 8.1 on a Centris 650 back in the day (can’t remember how much RAM it had), and it was... fine. It definitely wasn’t fast. I’m planning on putting 7.5.5 (probably) on my current Centris 650 whenever I get around to reloading it.
  8. mdeverhart

    SE/30 DiiMO accelerator cloning

    You’re absolutely right, Atmel does: https://www.microchip.com/design-centers/fpgas-and-plds/splds-cplds Altera discontinued theirs. Atmel got bought by Microsemi (before Microsemi got bought by Microchip), and Atmel’s FPGAs are listed on the Microsemi website. I didn’t realize that their CPLDs were on the Microchip site. I’ll need to dig through some data sheets and see if I can find a suitable device. I’ve had a little bit of time to look at this, but not a ton. Most of the logic is straightforward, but I’m trying to wrap my head around the feedback paths and the inversions/polarities on those paths. @Bolle What program did you use to dump the equations from the JED files? I’d like to try assembling and then disassembling some of my own logic to better understand some of those equations. Would you be willing to email me the JED files you extracted if I PM’d you my email address?
  9. mdeverhart

    LC Fan and Speaker Clicking

    It looks like there may be a significant amount of corrosion / cap goo under and around UB9, UB10, and UC9. If that’s the case (hard to tell from the pictures), you may need to remove those components and clean under them. I don’t have the schematics, so I’m not sure what those components do. I agree with your reading of the capacitor data sheet - those are all 100 uF, looks like 8 of them should be 10uF and only one 100uF: http://www.maccaps.com/MacCaps/Capacitor_Reference/Entries/1990/10/15_LC_I%2C_II%2C_III_Power_Supplies_2.html
  10. mdeverhart

    Dead 512k, rapid clicking?

    Nice, that’s good progress! Now you can at least start diagnosing the problems. Have you replaced the caps on the logic board yet? Can you read the code under the Sad Mac? If so, what is it?
  11. mdeverhart

    Mac Classic Oscillator needs to be jump started

    Glad you got it working!
  12. mdeverhart

    LC Fan and Speaker Clicking

    Sorry, but that’s not correct. You can go higher on the voltage rating if you want (e.g. use a 16V rated cap instead of a 10V rated one), but the capacitance value should match the original value. For power decoupling caps, the capacitance value is important for filtering out different frequencies, so you’ll often see a few large caps, a few medium caps, and a bunch of smaller value caps - the large caps filter the lower frequencies, the smaller the high frequencies. For in-circuit caps, the values are even more important, as they directly impact the operation of that part of a circuit. For example, a cap might be paired with a resistor to form an RC circuit, where the cap is designed to charge and discharge in a specific amount of time. Changing the cap value will change that time constant, which will cause that part of the circuit to operate poorly or not at all. If some of the 10uF caps have been incorrectly replaced with 100uF, I would highly recommend they be replaced with the proper values.
  13. mdeverhart

    Compact Mac Test Stand

    That is fantastic, good work! I can’t wait to see how it turns out.
  14. mdeverhart

    Just picked up a 512ke

    Sounds like a couple of serious scores! Congrats! (and I’m just a little jealous )
  15. mdeverhart

    Mac Classic Oscillator needs to be jump started

    Touching the probe to the crystal will add a small amount of capacitance to the circuit, which may be enough to jump start the oscillation. I would guess that either the crystal or the two capacitors next to it need to be replaced.