Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2022-01-13, 23:50

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

On pin 18 on the SRAM IC it get 3,8 volt, when the machine is turned off. And when it is turned on I get 0,012 volt. The VCC voltage on the SRAM IC is only 3,66 volt - that seems to be to low, it should be 5 volt I have pulled pin 18 to ground, but it did not do the trick - If pin 18 is ~0v when …

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-12-30, 11:40

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hey Carsten! Bummer you're having this issue too, it was a wiley one! If you've got a multimeter, you can prove the same issue I was having - I only used the scope because I was already using it while checking the address lines. Just need to see if that pin stays HIGH (should be around 5v) or gets …

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-12-22, 08:20

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Just as an update, I ended up replacing both the RTC and SRAM ICs to no avail. After consulting the boffins on comp.sys.ibm.ps2.hardware as recommended, they led me down a good track. Was able to confirm the RTC functionality perfectly, but the SRAM was not returning anything. Digging and probing …

---

Re: Fun thread: Things you thought you knew but were soooo wrong..

Posted on 2021-12-02, 07:18

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

All AMD GPUs since Vega and all nVidia GPUs since Maxwell use tile based rendering. All current consoles also use tile based rendering. Also XBOX 360 had onchip eSRAM to assist in holding framebuffer data and applying MSAA through tiling and XBOX ONE had enough eSRAM to hold the framebuffer so tile …

---

Re: Fun thread: Things you thought you knew but were soooo wrong..

Posted on 2021-12-02, 06:17

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

appiah4 wrote on 2021-12-02, 06:12: Tile based rendering did take over though (15 years or so later) Oh really? I read that some mobile graphics chipsets were using tile based rendering, but wasn't aware of anything else? I haven't really kept up with 3d rendering techniques since probably mid …

---

Re: Fun thread: Things you thought you knew but were soooo wrong..

Posted on 2021-12-02, 00:20

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I was a firm believer that tile based rendering in my beloved PowerVR Kyro2 would take over and give 3dfx and nVidia a run for their money, riiiight up until the Geforce3/4 just z-buffer brute forced their way into the lead

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-29, 22:17

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

can you describe the corrosion damage a bit? That sounds like a probable cause. Does the bios settings stick with a warm boot? if it only doesn't survive a cold boot, it sounds like the battery circuitry is likely to blame. The corrosion was only on the floppy drive, caused by leaked SMD …

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-29, 10:52

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay I've had it sitting for a few days now without the battery, and I remade a bunch of copies of the reference disk just in case. Same thing. I've also switched to a CRT monitor from the LCD I was using above, and the 2401 error I had attributed to the LCD is still there too, so I guess there's …

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-25, 06:43

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

No luck on the belt and braces clear, unfortunately. Left it overnight with the jumper in and battery and power out, booted up this morning to a 161/163, went through the usual procedure and on reboot it went back to the 162/163 and configuration data error boot loop.

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-23, 23:02

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I haven't shorted the jumper, but the machine was sitting on a shelf for 4-5 years without a battery or power... but yeah I'll give that a try too. Throwing everything at the wall at the moment, hopefully something sticks!

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-23, 22:42

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yep sorry, should have mentioned voltages there were fine too. I was able to get into the ref disk system checkout and run tests, and it's definitely finding something wrong on the planar. Not quite sure what this error is though, I can't find a definitive guide to what the diagnostic test error …

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-23, 08:00

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay then, all traces are healthy, no corrosion anywhere on the planar. On the MC146818A itself and during power off, I'm seeing a constant 4V between Vss and Vdd, and 5V when powered on - both are well within the acceptable range for that IC.

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-22, 23:25

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hmm... the trace corrosion was on the floppy drive from the leaked electros, but I guess that is directly above the circuitry between the battery and the RTC. I couldn't see anything obviously damaged on the planar, but I guess I should measure between the VBAT at the RTC/CMOS directly to be …

---

Re: IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-22, 22:19

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As noted, I've replaced the battery with a brand new one, and even used a benchtop supply in place of the battery to be absolutely sure that's not the problem.

---

Re: IBM PS/2 Model 70 won't auto-configure, help?

Posted on 2021-11-22, 11:43

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As an update, I was ... somehow able to get into the reference disk configuration menu, went in and set the time/date and manually set and saved the configuration. On reboot, it was still showing a 162/163 error so I'm guessing there's something wrong with the CMOS/SRAM storage chips identified here …

---

IBM PS/2 Model 70 won't keep configuration, help?

Posted on 2021-11-22, 06:28

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hey folks, trying to recover a PS/2 Model 70-386 I acquired recently, there have been a lot of repair work so far (PSU was dead, floppy had leaked caps and corroded traces) but I've finally got it booting and reading diskettes! The problem I'm facing now though, is that when I put the 70/80 …

---

Re: Can't identify 30-pin SIMM, help?

Posted on 2021-09-29, 03:36

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

BitWrangler wrote on 2021-09-29, 03:32: 1 MB, parity, 60ns, strawberry cream centers... ... maybe I tapped my inner toddler for the last bit. My favourite 😉 I really need a machine to be able to test these in, but until then I'm just sorting sorting sorting. Thanks!

---

Can't identify 30-pin SIMM, help?

Posted on 2021-09-29, 03:16

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hey folks, going through a big ole bag of RAM I just got and I can identify most of these SIMMs but these are eluding me. I have three identical sticks and none of them have any useful markings or stickers, and the ICs don't seem to match any regular SRAM markings that I'm used to decoding (41400, …

---

Re: Trying to identify some CPUs

Posted on 2021-09-29, 03:12

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I got these CPUs and for reference, the top was indeed a 486 DX2-50 and the bottom was a 486 DX2-66. Case closed!

---

Re: Trying to identify some CPUs

Posted on 2021-09-10, 09:34

by

by silvervest

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The top one must be a 486 DX2, notice the 1992 copyright. That's the release year for that CPU. That's a good hint! It looks like the SX626 486 DX2-50 has a CPUID of 432, which is on the bottom markings of this one. The bottom of the SX807 looks very similar to this as well! Maybe the closest I'll …

---