Uploaded October 2022 | Updated September 2026, 2 weeks ago
There is a lot of argument if the missing ROR instruction is a bug or not. Whatever it is, it was clearly intended to be there but was left out at the last minute, likely due to time constraints for the release for the CPU. Just a handful of months later an updated data sheet was released saying the instruction would be added into future versions of the chip. The ROM we wrote is able to identify (in a running system) if you have a CPU that has a non-functional ROR instruction.
--- Info
Possible TTL shift register
TI 1A5008
--- Video Links
ROM to test for the ROR bug on the Apple II:
github.com/misterblack1/6502_ror_bug_test
Pagetable ROR bug article:
pagetable.com/?p=406
A viewer @DaftdogUK discovered what this is! See Page 102:
archive.org/details/kilobaudmagazine-1979-09/page/n101/mode/2up
MOS 6502 by Chuck Peddle:
en.wikipedia.org/wiki/MOS_Technology_6502
SWTPC 6800:
en.wikipedia.org/wiki/SWTPC_6800
Frank's Channel (IZ8DWF)
youtube.com/c/iz8dwf/videos
Tech Time Traveller's Channel:
youtube.com/c/TechTimeTraveller/videos
The TV Typewriter (Shift register storage):
youtube.com/watch?v=b-bFV8fHekk
Link to dumped 256 byte ROM
github.com/misterblack1/6502_ror_bug_test/blob/main/6502-bootrom.bin
Adrian's Digital Basement Merch store:
my-store-c82bd2-2.creator-spring.com
Adrian's Digital Basement ][ (Second Channel)
youtube.com/channel/UCbtwi4wK1YXd9AyV_4UcE6g
Support the channel on Patreon:
patreon.com/adriansdigitalbasement
-- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/s.nl/it.A/id.1602/.f
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
rigolna.com/products/digital-oscilloscopes/1000z
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
amzn.to/2wG4tlP
aliexpress.com/item/33000308958.html
TS100 Soldering Iron:
amzn.to/2K36dJ5
ebay.com/itm/TS100-65W-MINI-Digital-OLED-Programmable-Soldering-Iron-Anti-static-Structure/113382669853
EEVBlog 121GW Multimeter:
eevblog.com/product/121gw
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
ebay.com/itm/USB-Logic-DSLogic-Basic-Analyzer-16Ch-100MHz-4Ch-400MHz-Xilinx-Spartan-6-FPGA/202543965672
Magnetic Screw Holder:
amzn.to/3b8LOhG
harborfreight.com/4-inch-magnetic-parts-tray-90566.html
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
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)
retrotink.com
Plato (Clone) Side Cutters: (order five)
ebay.com/itm/1-2-5-10PCS-Micro-Scissor-125mm-PLATO-170-Electronics-Cutter-Side-Cutting-Pliers/163458746184
Heat Sinks:
aliexpress.com/item/32537183709.html
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/misterblack1?tab=repositories
Commodore Computer Club / Vancouver, WA – Portland, OR – PDX Commodore Users Group
commodorecomputerclub.com
--- Instructional videos
My video on damage-free chip removal:
youtube.com/watch?v=XQVjwPsVFd8
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino
There is a lot of argument if the missing ROR instruction is a bug or not. Whatever it is, it was clearly intended to be there but was left out at the last minute, likely due to time constraints for the release for the CPU. Just a handful of months later an updated data sheet was released saying the instruction would be added into future versions of the chip. The ROM we wrote is able to identify (in a running system) if you have a CPU that has a non-functional ROR instruction.
--- Info
Possible TTL shift register
TI 1A5008
--- Video Links
ROM to test for the ROR bug on the Apple II:
github.com/misterblack1/6502_ror_bug_test
Pagetable ROR bug article:
pagetable.com/?p=406
A viewer @DaftdogUK discovered what this is! See Page 102:
archive.org/details/kilobaudmagazine-1979-09/page/n101/mode/2up
MOS 6502 by Chuck Peddle:
en.wikipedia.org/wiki/MOS_Technology_6502
SWTPC 6800:
en.wikipedia.org/wiki/SWTPC_6800
Frank's Channel (IZ8DWF)
youtube.com/c/iz8dwf/videos
Tech Time Traveller's Channel:
youtube.com/c/TechTimeTraveller/videos
The TV Typewriter (Shift register storage):
youtube.com/watch?v=b-bFV8fHekk
Link to dumped 256 byte ROM
github.com/misterblack1/6502_ror_bug_test/blob/main/6502-bootrom.bin
Adrian's Digital Basement Merch store:
my-store-c82bd2-2.creator-spring.com
Adrian's Digital Basement ][ (Second Channel)
youtube.com/channel/UCbtwi4wK1YXd9AyV_4UcE6g
Support the channel on Patreon:
patreon.com/adriansdigitalbasement
-- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/s.nl/it.A/id.1602/.f
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
rigolna.com/products/digital-oscilloscopes/1000z
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
amzn.to/2wG4tlP
aliexpress.com/item/33000308958.html
TS100 Soldering Iron:
amzn.to/2K36dJ5
ebay.com/itm/TS100-65W-MINI-Digital-OLED-Programmable-Soldering-Iron-Anti-static-Structure/113382669853
EEVBlog 121GW Multimeter:
eevblog.com/product/121gw
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
ebay.com/itm/USB-Logic-DSLogic-Basic-Analyzer-16Ch-100MHz-4Ch-400MHz-Xilinx-Spartan-6-FPGA/202543965672
Magnetic Screw Holder:
amzn.to/3b8LOhG
harborfreight.com/4-inch-magnetic-parts-tray-90566.html
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
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)
retrotink.com
Plato (Clone) Side Cutters: (order five)
ebay.com/itm/1-2-5-10PCS-Micro-Scissor-125mm-PLATO-170-Electronics-Cutter-Side-Cutting-Pliers/163458746184
Heat Sinks:
aliexpress.com/item/32537183709.html
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/misterblack1?tab=repositories
Commodore Computer Club / Vancouver, WA – Portland, OR – PDX Commodore Users Group
commodorecomputerclub.com
--- Instructional videos
My video on damage-free chip removal:
youtube.com/watch?v=XQVjwPsVFd8
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino
