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AuthorTopic: A500 512KB Chip VS A500 1MB Chip  (Read 4565 times)

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Offline BLTCON0

Re: A500 512KB Chip VS A500 1MB Chip
« Reply #30 on: September 04, 2017, 08:32:06 AM »
@kirk_m
You need a DPDT switch (like the one you linked to).
DPDT = 1P [1T | 2T] + 2P [1T | 2T]

1P = pin 2 of JP2 then 1T = pin1 of JP2 and 2T = pin3 of JP2
2P = pin 2 of JP7A then 1T = pin1 of JP7A and 2T = unconnected

This way, the 1P1T + 2P1T setting will enable 512 chip + 512 ranger
and the 1P2T + 2P2T setting will enable 1 MB chip.
 

Offline kirk_m

Re: A500 512KB Chip VS A500 1MB Chip
« Reply #31 on: September 04, 2017, 07:37:51 PM »
Thanks!  Do you know if such a switch setup will work if I have a megachip installed on this a500?  Currently, I do, so there are really 2 megs of chip in there.
-/- A500 & ACA500 & ACA1233n -/- A500 Tower & VAMPiRE II 500+ -/- A2000 & BLiZZARD 2060 -/- A3000 & CYBERSTORM MKII 040 -/- A1200 & BLiZZARD 1230 MK IV -/- A1200 & BLiZZARD 1260 -/- A4000 & 3640 -/-
 

Offline BLTCON0

Re: A500 512KB Chip VS A500 1MB Chip
« Reply #32 on: September 04, 2017, 09:46:31 PM »
Quote from: kirk_m;830369
Thanks!  Do you know if such a switch setup will work if I have a megachip installed on this a500?  Currently, I do, so there are really 2 megs of chip in there.


I don't, never tried it, but it doesn't hurt to try. You could even use a 3PDT switch, with the 3rd pole for the megachip wire to Gary.

DPDT = 1P [1T | 2T] + 2P [1T | 2T] + 3P [1T | 2T]

1P = pin 2 of JP2 then 1T = pin1 of JP2 and 2T = pin3 of JP2
2P = pin 2 of JP7A then 1T = pin1 of JP7A and 2T = unconnected
3P = wire from Megachip then 1T = unconnected and 2T = Gary pin36

This way, the 1P1T + 2P1T + 3P1T setting would supposedly enable 512 chip + 512 ranger (with the remaining 1 MB ignored)
and the 1P2T + 2P2T + 3P2T setting would enable the full 2 MB chip RAM.
 

Offline Matt_H

Re: A500 512KB Chip VS A500 1MB Chip
« Reply #33 on: September 05, 2017, 04:38:48 PM »
Before playing with hardware switches to undo the 1MB Chip mod (which was an official Commodore upgrade), try Degrader for the very few programs that choke on 1MB+ of Chip RAM.
 

Offline Oldsmobile_Mike

Re: A500 512KB Chip VS A500 1MB Chip
« Reply #34 on: September 05, 2017, 05:08:19 PM »
Quote from: Matt_H;830377
Before playing with hardware switches to undo the 1MB Chip mod (which was an official Commodore upgrade), try Degrader for the very few programs that choke on 1MB+ of Chip RAM.

+1

IMHO no reason to "degrade" any system in this way in 2017.  But good luck with that, am kind of curious to know what will happen if you try it with the Megachip.  I guess in theory you could set it to 2MB/1MB/512K.  Interesting to try, I suppose?  ;)
Amiga 500: 2MB Chip|16MB Fast|30MHz 68030+68882|3.9|Indivision ECS|GVP A500HD+|Mechware card reader + 8GB CF|Cocolino|SCSI DVD-RAM
Amiga 2000: 2MB Chip|136MB Fast|50MHz 68060|3.9|Indivision ECS + GVP Spectrum|Mechware card reader + 8GB CF|AD516|X-Surf 100|RapidRoad|Cocolino|SCSI CD-RW
 Amiga videos and other misc. stuff at https://www.youtube.com/CompTechMike/videos
 

Offline BLTCON0

Re: A500 512KB Chip VS A500 1MB Chip
« Reply #35 on: September 05, 2017, 05:42:57 PM »
Quote from: Matt_H;830377
Before playing with hardware switches to undo the 1MB Chip mod (which was an official Commodore upgrade)

Even though Commodore made the instructions available, and made a PCB revision tailor-made for the upgrade (6A/7), they also made it very clear that at least for the A500 it would not be a supported configuration.
On the other hand, 2 MB chip RAM on the rev6A A500 using the 8372B Agnus in its "natural" mode (single bank of four 1Mx4 chips) clearly had their blessings.

That said there's nothing wrong of course with the 1 MB chip RAM mod, Commodore not supporting it was just a marketing decision.
 

Offline Matt_H

Re: A500 512KB Chip VS A500 1MB Chip
« Reply #36 on: September 07, 2017, 01:51:14 AM »
Quote from: BLTCON0;830379
Even though Commodore made the instructions available, and made a PCB revision tailor-made for the upgrade (6A/7), they also made it very clear that at least for the A500 it would not be a supported configuration.
On the other hand, 2 MB chip RAM on the rev6A A500 using the 8372B Agnus in its "natural" mode (single bank of four 1Mx4 chips) clearly had their blessings.

That said there's nothing wrong of course with the 1 MB chip RAM mod, Commodore not supporting it was just a marketing decision.


I suppose that depends on what the definition of "not supported" is. It was a *required* procedure in order to use the A570 and dealers would perform it under warranty.
 

Offline BLTCON0

Re: A500 512KB Chip VS A500 1MB Chip
« Reply #37 on: September 07, 2017, 08:40:48 AM »
I guess so... but as far as shipments go, I don't think they ever shipped a 1 MB chip RAM configured A500. This held true all the way up to the last rev8A A500s which shipped with the trapdoor still configured for $C000000 'ranger' RAM.
There is mention of this "policy" somewhere but I can't seem to locate the document anymore :-(