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For people with 2023.08 BlueSCSIv2 designs (see attached PDF schematic) which resistors need to be changed, and to what values, to avoid trouble when used on a 5120 or 5126 Macintosh Portable?

If we ignore the RAM card slowdown issues mentioned earlier in this thread and just focus on what you are describing when BlueSCSI v2 is used, what is the end result in terms of how BSv2 operates with the Portable? Does this cause BSv2 to lockup? Noticeably slow down? Or does it seem to operate...

Well, I did further testing this evening, at the stock clock speed of 33MHz with the 8MB universal ROM SIMM that @Jockelill helped to create, and I provided him some feedback. (Basically, it works to kill the painfully slow RAM checking at cold boot, but booting from ROM still has bugs that...

You can see that in my photo here... In the above photo, 88916 chip Pin-8 is the SYNC input, 3rd pad from the right. Pin-9 is Ground. Note how the GND from Pin-9 loops around the Pin-8 trace.

@YMK thank you for your kindness in replying, and I appreciate that observation. The answer is this... source: https://resources.ema-eda.com/home/2023-design-recommendations-for-pcb-impedance-control But let's ignore that for now and assume a fixed Zo impedance that never changes. How do...

As I mentioned earlier in this thread, there are TERMINATION RESISTORS used on the 2X_Q output of the 88916DW chip, which leads to PCLK on the 68040 CPU. So for example, when the CPU clock speed is 33MHz, PCLK will be twice that at 66MHz. And that is really the reason the 88916 chip is used --...

I am happy to report that I was able to boot into the following OS's, both from my internal spinning platter HDD and an externally connected BlueSCSI v1: System 7.1 System 7.5.5 System 7.6.1 OS 8.1 I then put the SD card into my BlueSCSI v2 and retested, and all was well with that. I am still...

I have been feeling absolutely terrible all month, and completely exhausted every day after work, which is why this has take so long. But I was able to solder in the 88916DW80 chip that @trag so graciously sent to me, and I am pleased to report that I get a bong and boot! Spicy is...

My question pertains to BlueSCSI v2 on the 5126 Backlit Macintosh Portable. A friend very kindly and generously mailed me a populated BlueSCSIv2 board which has a connector for use with the SCSI ribbon cable of a Macintosh Portable. (Sorry, no photo, as I left it at the office.) So unlike...

I obtained this schematic from someone else but will avoid naming them for now. I am very thankful to have obtained it; but honestly, it's not a very good scan. All the gray parts are very hard to read. But everything other than that is quite good, and you'll find it useful when diagnosing...

@Kai Robinson In answer to your comment about the SCSI clock, my LC575 motherboard already has a 0Ω resistor on at R120, with nothing at R106. The schematic below is for the LC575 and the gray parts are infuriatingly hard to read, but you can see that it says "Stuff R120 for 33/40MHz systems"...

I apologize for my delayed reply. I've been extremely busy lately, and on top of that, I've been feeling rather terrible all month. No time to visit the doctor until early March. :sick: It is also the reason I've not had a single moment of time to do any video work for my YouTube channel. I...

I would like to once again humbly thank @trag for having so kindly shipped me some MC88916DW80 and DW55 chips. They arrived today and I was able to put a few to the test in my test jig. I measured current consumption first. I found that a good DW55 draws 75mA while a DW80 draws only 67mA...

Here's my test using Spicy O'Clock, which allows me to satisfy the XC88916DW55 chip's minimum input frequency requirement. So basically, this is proving the chip is bad. I will provide another update when the chips from @trag arrive. Thanks again, @trag!

Thanks for the reminder, Kai. I also just remembered that I could use the output from Spicy O'Clock too. So I will give both of those a try and see what happens.

@trag I've been exchanging PMs with someone who asked me to do various tests. I made a couple videos of those tests, where I had the XC88916DW55 chip desoldered from the LC575 motherboard and placed inside an SMD to DIP socket for my breadboard. Even without any SYNC input, I get roughly a...

I thought long and hard about which VGA mod to do. Because I lacked experience, I deferred to the experts and did the standard VGA mod, which is a low voltage mod that puts less strain on the Analog Board. But if I were to do it again, I probably would have just swapped out the spinning hard...

I'm thrilled to see you have your Color Classic working nicely, Kenny. @Kay K.M.Mods kindly got me started with the Color Classic a few years ago, and I've been hooked since. The machine is almost like a drug. Before owning one, I didn't think much of the industrial design, but then after...

I removed the XC88916DW55 chip this evening. It's all ready for a replacement. And I do hope that is the fix. Even so, I won't know until I try a chip swap.

I've not heard back from Kai, so it could be he can't find his stash. I emailed you just now about acquiring some of your chips. My DW55 chip should theoretically only handle up to 55MHz on the 2X output. Meaning, there's also a 1X output. For example, if you run an 040 CPU at 25MHz (1x...