#vintagecomputing — Public Fediverse posts
Live and recent posts from across the Fediverse tagged #vintagecomputing, aggregated by home.social.
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#retrocomputing #vintagecomputing #ibm1620
The 1620 had 60-some-odd triggers (or "latches", nowadays "flip-flops".)
My first #python design was a dictionary of `TriggerState` objects. The idea was to use a slightly richer API than what `bool` objects offered.
`TRIGGER["COMP"].on()`, instead of `TRIGGER["COMP"] = True`.
`timeit` says an enum and a set is faster. `TRIGGER.add(Trg.COMP)` takes about ½ the time.
Now that the unit test suite passes, refactoring is in order.
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Clippy even ended up here on a PowerBook in Mac OS on Excel, it probably helped that Microsoft invested a ton of money into Apple to keep it from floundering. Strange how the world works.
#tech #vintagecomputing #retrocomputing #it #vintagetech #excel #clippy -
Commodore 1702 Repair Stumps Adrian’s Digital Basement
#Commodore1702 #Commodore64 #AdriansDigitalBasement #CRTRepair #RetroComputing #VintageComputing #Commodore #RetroTech
https://theoasisbbs.com/commodore-1702-repair-stumps-adrians-digital-basement/?fsp_sid=14937 -
Nuanced state changes in the True/Complement Switch and the Memory Address Register (MAR).
The T/C Switch is the units position of the Digit/Branch register.(How to minimize cost and maximize confusion: reuse registers for different nefarious purposes.)
A "Complement + Carry In" happens in two places.
1. Complement. Update the T/C Switch.
2. Add 1. Some transient state in a path from T/C Switch to MAR.
Need. More. Coffee.
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I thought I'd sorted this out. Add and Subtract seem to work.
Compare is failing. It's a special Subtract that doesn't save a result.
How hard can it be?
But... Maybe I haven't really manufactured the right unit test cases for Add and Subtract to demonstrate this 9's complement-with-carry-in feature.
So. Much. Thinking.
Need. More. Coffee.
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#retrocomputing #vintagecomputing #ibm1620
Today's brain cramp: Figure 13-7, which "explains" how the ADD table works (Yes, the 1620 had a memory lookup for addition; CADET: Can't Add Doesn't Even Try.)
I need a refresher on how 9's (and 10's) complement arithmetic works.
(I nearly failed this course in college 50 years ago: I didn't get it then, and I certainly can't recollect what I didn't get in the first place.)
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Related to the post about USB-SCSI adapters (https://fosstodon.org/@sxa/117418002783874212) I have a few - now ancient - IBM PS/2 model 95s which used SCSI drives. Some with Pentium 60 CPUs, some 486. Most aren't fully starting up at the moment (looking for reference disks or are passworded) but one did.
Apparently it's got Solaris 2 6 on it. Is clearly forgotten (a) that Solaris had MCA support and (b) that I'd installed it on one of these!
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Related to the post about USB-SCSI adapters I have a few - now ancient - IBM PS/2 model 95s which used SCSI drives. Some with Pentium 60 CPUs, some 486. Most aren't fully starting up at the moment (looking for reference disks or are passworded) but one did.
Apparently it's got Solaris 2 6 on it. Is clearly forgotten (a) that Solaris had MCA support and (b) that I'd installed it on one of these!
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Related to the post about USB-SCSI adapters I have a few - now ancient - IBM PS/2 model 95s which used SCSI drives. Some with Pentium 60 CPUs, some 486 (I never got one with the "Holy Grail" of a P90). Most aren't starting up at the moment (looking for reference disks or are passworded) but one did.
Apparently it's got Solaris 2 6 on it. Is clearly forgotten (a) that Solaris had MCA support and (b) that I'd installed it on one of these!
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Scriptee development blog part 25 is alive (forgot to post last night). This one discusses the RUN command implementation. I had trouble with this early on and set it aside.
