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Tube❄️Time

i've been reading the Amiga 1000 Assembly and Component Level Repair manual and found this interesting memory map diagram. notice what is stored from F00000-F7FFFF? it is marked "CART." could this have been for a game cartridge slot? the Comspec SCSI card puts its autostart ROM here.

16 comments
Jope replied to Tube❄️Time

@tubetime most likely it is a remnant of the old game console design, but it was also heavily used in os development for temporarily loading new ROM modules when testing, and also many expansions used it for their roms if they did not do autoconfigure.

Tube❄️Time replied to Tube❄️Time

here's the Comspec SCSI drive enclosure. it's a bit of a beast and supports two half height drives. Comspec was definitely Canadian; check out that mounting screw!

Aaron Sawdey, Ph.D. replied to Tube❄️Time

@tubetime Brings back many fond memories of ST-225Ns!

And the vias on that board are strangely attractive…

Tube❄️Time replied to Tube❄️Time

drive enclosure will not power up 😔

Tube❄️Time replied to Tube❄️Time

the controller is the UC3842. hmm.

Tube❄️Time replied to Tube❄️Time

the circuit is similar to the "typical application circuit" and it looks like there are two small electrolytic capacitors on the UC3842 VCC rail that have gone super leaky, preventing it from bootstrapping and powering up. it was a simple enough fix.

Tube❄️Time replied to Tube❄️Time

it's waiting for the HDD to spin up and initialize.

Tube❄️Time replied to Tube❄️Time

the yellow screen means it is trying to load the Kickstart off of a special drive partition.

Tube❄️Time replied to Tube❄️Time

oh that's not good, it blinks red 8 times. this means the drive failed the SCSI mode sense command for some reason. weird.

Chartreuse replied to Tube❄️Time

@tubetime Is that something special added by the controller interface? Or is the onboard boot room able to look for kickstart other than the floppy disk?

Tube❄️Time replied to Chartreuse

@ChartreuseK the onboard (non kickstart) ROM looks at F00000 and finds the controller ROM, which then takes over the boot process. i think this was originally for supporting game cartridges

Chartreuse replied to Tube❄️Time

@tubetime Ah okay, didn't know that was a thing it did. Certainly a nice feature to not need the kickstart disk to boot a hard disk

vxo replied to Tube❄️Time

@tubetime I've run into this in audio amplifiers too. They have a bootstrap pin which is connected to a RC network off a supply voltage - the cap charges up slowly once the power comes on and eventually lets the amp come out of inhibit. It's a power up thump avoidance thingy.

And yeah, when the cap fails short, the amp plays dead

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