Can someone tell me what the difference between a A500(+) Rev. 8A and 8A.1 motherboards is?
My take on this: It's just a configuration change (memory and/or Agnus).
My take on this: It's just a configuration change (memory and/or Agnus).
Difference A500(+) Rev. 8A and 8A.1
- Thread starter Zorro
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I think rev 8A is later mobo only for original Amiga 500 plus with ECS , battery installed ,kick 37.175 and 1 mb on board
Rev 8a1 there is only "plus" sign on mobo , chipset OCS , agnus ready for 2mb 8375 , kicktarst 1.3, no battery no RTC
8A1 is Amiga 500 plus ""READY ""
rev 8a1 is good mobo for cheap 2 mb chip upgrade :dry:
Rev 8a1 there is only "plus" sign on mobo , chipset OCS , agnus ready for 2mb 8375 , kicktarst 1.3, no battery no RTC
8A1 is Amiga 500 plus ""READY ""
rev 8a1 is good mobo for cheap 2 mb chip upgrade :dry:
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sure, that is not my intention but this is what i have. Moreover, maybe the most interesting one, I had an another A500+ and as far as i remember, it had OCS chipset with KS2.04... to cut a long story short, Commodore had sold lots of mixed products as 500 and A500+
Based on everything I've read ever, including the original manuals for the A500+, all A500+'s are ECS with fat agnus & super denise.
If you have one that is OCS, then it's likely a modified A500 (possibly in an A500+ case)
If you have one that is OCS, then it's likely a modified A500 (possibly in an A500+ case)
A theory I have is it may have to do with accepting the newer (Vbb) 318069 version of the 8375 2 Mb Agnus or the older (non Vbb) 390544 one.
A500+ boards typically shipped with the 390544 version. But very late ones came equipped with the 318069 version.
So one can have
1. A rev8A board with the 390544 Agnus (match)
2. A rev8A board with the 318069 version (mismatch)
3. A rev8A board with the 318069 version and a capacitor soldered between two Agnus pins on the underside of the board as a fix (match, sticker on the board should read 8A.1, PCB etching 8A)
4. A 'true' rev8A.1 board (i.e. the PCB itself has 8A.1 etched) which should directly provide for the 318069 Agnus and normally come equipped with it.
A500+ boards typically shipped with the 390544 version. But very late ones came equipped with the 318069 version.
So one can have
1. A rev8A board with the 390544 Agnus (match)
2. A rev8A board with the 318069 version (mismatch)
3. A rev8A board with the 318069 version and a capacitor soldered between two Agnus pins on the underside of the board as a fix (match, sticker on the board should read 8A.1, PCB etching 8A)
4. A 'true' rev8A.1 board (i.e. the PCB itself has 8A.1 etched) which should directly provide for the 318069 Agnus and normally come equipped with it.
Bastich
Active member
I recently got a full A500+ with an 8A1 board in it (no battery damage for once). It has a later model number (sliver sticker on the back) than my other 8A boards. Someone on the net mentioned that there may have been a slightly different Denise chip on some of the 8A1 boards. Is there any truth in this?
8a1 rev is only PLUS marked but there is OCS , 512 kb and no battery like in full Amiga 500 plus mobo
big positive for his mobo is AGNUS 8375 which support full 2mb chip , this board can easy upgrade to full Amiga 500 plus ! and you got nice board with no battery damage ! like often in Amiga 500 plus 8a
big positive for his mobo is AGNUS 8375 which support full 2mb chip , this board can easy upgrade to full Amiga 500 plus ! and you got nice board with no battery damage ! like often in Amiga 500 plus 8a
Layout change in the battery charging circuit. One can see D911/912 crossing another part on Rev8a but on Rev8a.1 board it was corrected.
Hi there, I have mentioned board, A500, rev8a. It has ks1.3, OCS and no battery...It has also the 8375 Fat agnus chip, with part number 390544-01 [C=CSG, 4791 20, no VBB printed].
I have recently bought an A500+ trapdoor expansion from this thread [https://www.amibay.com/showthread.php?90976-Amiga-500-A500-1MB-trapdoor-memory]for this mobo, but it was not detected, what could be wrong?
Will upload photos of the A500 board just in case.
Thanks for viewing..
I have recently bought an A500+ trapdoor expansion from this thread [https://www.amibay.com/showthread.php?90976-Amiga-500-A500-1MB-trapdoor-memory]for this mobo, but it was not detected, what could be wrong?
Will upload photos of the A500 board just in case.
Thanks for viewing..
@DesktopDynamite
You may have the A500+ motherboard (rev8A) but in your case it has been configured as a plain A500.
As it is, your motherboard takes regular 512 KB trapdoor expansions as designed for the standard A500, and maps them to $C00000 (ranger RAM).
The expansion you bought is meant for the full A500+ motherboard, so your rev8A must be upgraded to full A500+ specs (another 512 KB of RAM onboard plus a missing chip and related modifications). That way you'll have a full 2 MB of chip RAM.
If you don't want to do such an extensive modification, you could try connecting Gary pin #32 to ground and see if this gives you at least an extra 512 KB as Fast (ranger) RAM.
Or maybe just changing the JP2 jumper setting could give you an extra 512 KB of chip RAM.
But without upconverting the board to full A500+ specs (*), you certainly won't be able to utilise the full 1 MB of the expansion.
(*) The real time clock circuitry may be omitted from such an upconversion as it has nothing to do with RAM.
You may have the A500+ motherboard (rev8A) but in your case it has been configured as a plain A500.
As it is, your motherboard takes regular 512 KB trapdoor expansions as designed for the standard A500, and maps them to $C00000 (ranger RAM).
The expansion you bought is meant for the full A500+ motherboard, so your rev8A must be upgraded to full A500+ specs (another 512 KB of RAM onboard plus a missing chip and related modifications). That way you'll have a full 2 MB of chip RAM.
If you don't want to do such an extensive modification, you could try connecting Gary pin #32 to ground and see if this gives you at least an extra 512 KB as Fast (ranger) RAM.
Or maybe just changing the JP2 jumper setting could give you an extra 512 KB of chip RAM.
But without upconverting the board to full A500+ specs (*), you certainly won't be able to utilise the full 1 MB of the expansion.
(*) The real time clock circuitry may be omitted from such an upconversion as it has nothing to do with RAM.
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Just a question: converting the A500+ motherboard (rev8A) configured as a plain A500 into a full full A500+ specs but ometting the the time clock circuitry, and using the new ram expansion od 512Kb/1Mb of chip ram with the battery, the clock will function as expected?
https://www.amibay.com/showthread.php?90920-New-A501-Style-1MB-512MB-Trapdoor-RAM-expansions-for-A500-A500-w-Clock
https://www.amibay.com/showthread.php?90920-New-A501-Style-1MB-512MB-Trapdoor-RAM-expansions-for-A500-A500-w-Clock
Thelemorf
New member
IF JP9 is closed the Rev8A and A.1 boards will work with external RTC
Hi folks,
does anybody knows where can i read about the necessary steps to upgrade 8A to real 8A+? It is quite interesteng, cause i picked up one A500 with non-working drive, after dismantling it turned out that she had an A500+ 8A board inside, 390544 Agnus and 8362R8 DENISE without battery installed. However, 4 RAM chips and U32 are unpopulated..?
UPDATE:
found an old Kipper's post about this mod:
http://eab.abime.net/showthread.php?t=77705
does anybody knows where can i read about the necessary steps to upgrade 8A to real 8A+? It is quite interesteng, cause i picked up one A500 with non-working drive, after dismantling it turned out that she had an A500+ 8A board inside, 390544 Agnus and 8362R8 DENISE without battery installed. However, 4 RAM chips and U32 are unpopulated..?
UPDATE:
found an old Kipper's post about this mod:
http://eab.abime.net/showthread.php?t=77705
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Thelemorf
New member
Just check out the differences in the photos on http://www.bigbookofamigahardware.com/
