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Second channel: I might have to give up on fixing this motherboard with RAM issues (Patreon)

Published:
2024-05-12 19:47:14
Imported:
2024-05

Content

Hello my patrons! The RAM issues continue on this second channel video with the PC XT clone motherboard which refuses to get fixed. In this second part, I really try to dig deep into what's going on with it to hopefully get to the bottom of what's happening with the random RAM errors.

In other news, I have two confirmed VCF dates so far this year:

VCF Southwest in Dallas - June 14-16, 2024

VCF Midwest in Chicago - September 7-8 2024

So if you are thinking of attending either, I will see you there! I will announce any other shows which I will be going to once the plans are firmed up.

Back to the motherboard, after you have watched this whole video, if you have any further thoughts on what might be happening, I'm all ears!

Thanks for all your support!

Direct link: https://www.youtube.com/watch?v=GMh5YUbLqLs

Files

I might have to give up on fixing this motherboard with RAM issues

The Meme continues! This broken PC XT clone motherboard with RAM problems continues to kick my butt. Can I finally get to the bottom of what's wrong with this motherboard? -- Video Links Broken Book8088 unboxing: https://www.youtube.com/watch?v=m3ETdhOuZ2w Book8088 Repair: https://www.youtube.com/watch?v=DAPCi-TQiy8 Turbo XT / Super XT BIOS: https://github.com/virtualxt/pcxtbios SuperSoft Diagnostic ROM: https://www.minuszerodegrees.net/supersoft_landmark/Supersoft%20Landmark%20ROM.htm Adrian's Digital Basement Merch store: https://my-store-c82bd2-2.creator-spring.com/ Support the channel on Patreon: https://www.patreon.com/adriansdigitalbasement Adrian's Digital Basement (Main Channel) https://www.youtube.com/channel/UCE5dIscvDxrb7CD5uiJJOiw My GitHub repository: https://github.com/misterblack1?tab=repositories -- Tools Deoxit D5: https://amzn.to/2VvOKy1 http://store.caig.com/s.nl/it.A/id.1602/.f O-Ring Pick Set: (I use these to lift chips off boards) https://amzn.to/3a9x54J Elenco Electronics LP-560 Logic Probe: https://amzn.to/2VrT5lW Hakko FR301 Desoldering Iron: https://amzn.to/2ye6xC0 Rigol DS1054Z Four Channel Oscilloscope: https://www.rigolna.com/products/digital-oscilloscopes/1000z/ Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier: https://amzn.to/3adRbuy TL866II Plus Chip Tester and EPROM programmer: (The MiniPro) https://amzn.to/2wG4tlP https://www.aliexpress.com/item/33000308958.html TS100 Soldering Iron: https://amzn.to/2K36dJ5 https://www.ebay.com/itm/TS100-65W-MINI-Digital-OLED-Programmable-Soldering-Iron-Anti-static-Structure/113382669853 EEVBlog 121GW Multimeter: https://www.eevblog.com/product/121gw/ DSLogic Basic Logic Analyzer: https://amzn.to/2RDSDQw https://www.ebay.com/itm/USB-Logic-DSLogic-Basic-Analyzer-16Ch-100MHz-4Ch-400MHz-Xilinx-Spartan-6-FPGA/202543965672 Magnetic Screw Holder: https://amzn.to/3b8LOhG https://www.harborfreight.com/4-inch-magnetic-parts-tray-90566.html Universal ZIP sockets: (clones, used on my ZIF-64 test machine) https://www.ebay.com/itm/14-16-18-20-24-28-32-40-pin-IC-Test-Universal-ZIF-Socket-Fs/303206721971 RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI) http://www.retrotink.com/ Plato (Clone) Side Cutters: (order five) https://www.ebay.com/itm/1-2-5-10PCS-Micro-Scissor-125mm-PLATO-170-Electronics-Cutter-Side-Cutting-Pliers/163458746184 Heat Sinks: https://www.aliexpress.com/item/32537183709.html Little squeezy bottles: (available elsewhere too) https://amzn.to/3b8LOOI --- Instructional videos My video on damage-free chip removal: https://www.youtube.com/watch?v=XQVjwPsVFd8 --- Music Intro music and other tracks by: Nathan Divino @itsnathandivino

Comments

Andy Hu

Hi Adrian. I can write a RAM march test ROM for the PC if you would like to collaborate.

Ron

Adrian, my guess is the selection logic for the memory banking. With no memory in the upper banks everything works because even if the upper banks were inappropriately selected they will not interfere. But as soon as there is real ram in the upper banks then simultaneous selection would generate RAM crosstalk. So either the upper banks are intermittently selected when they shouldn't be, or the lower bank is not being fully deselected when upper banks are active.

J and J's 8-bit Retro and Repair
>>138147083

Ron, I came to the same conclusion and just noticed your message. It is almost like either it is selecting banks at the wrong time or multiple banks at once, but we would expect to see conflicts on the RAM data bus on the scope if it were selecting multiple banks. It is quite possible there is a poor sync when bank selection is happening leading to some overlap. The DRAM refresh then could be selecting banks when refreshing, but CPU RAM access tries to get back to the bank it was looking at, but due to addressing slew it didn't switch in time. The DMA might not be affected, but as soon as the CPU tries to see its RAM it is accessing the wrong place for a fraction of time. Might not be noticeable on the scope if that were the case and it would look like gradual or random corruption of RAM.

Aurelius

When are they going to have a VCF in Toronto >:(