Cant memory expand my OS2 A500

Antiriad · 01 October 2002, 22:03

Hello all,

I bought a 500 about five years ago and have always been bemused by it. Its a 512k model with the old brown C= logo, but it has OS2.0.

Now, can i assume that any A500s that came with OS2.0 were the A500+'s that had 1MB RAM and the new white C= badge?

Therefore, assuming that the reason it has this is a custom jobby, can this explain why the f***er continually Gurus itself for several minutes after its booted up? Its only calm when i have the A500HD+ connected which adds 4MB Fast Ram. Does OS2 require 1MB to run???

The second thing is that the b*****d wont accept any trapdoor upgrades that work perfectly well on my other A500. Could this be related?

Any ideas would be appreciated. My principle prob is that id like more chip ram on it, but i suspect thats not possible without some soldering on the motherboard.

Or buying a A500+ of course

01 October 2002, 22:08

Your a5oo's original kickrom is replaced by a 2.0 one

Miggy2TheMax · 02 October 2002, 05:32

sounds like its a stock 500 with 2.0 roms, like burseg says. Anyhow there could be a couple of reasons why the trapdoor expansion may not be working, I'd say the main reason would be because someone tried out a 1mb chip hack that went wrong.

So I'd say you are going to have to open up your 500 and first identify what motherboard revision you got. If rev 5 read up the article below refer to section : "vii. 1Mb of Motherboard Memory on the Rev. 5"

http://wuarchive.wustl.edu/~aminet/h...k/500hacks.txt

If rev 6 then your jumpers[1] are out of wack cos someone tried a hardware hack that went wrong and forgot to put the jumpers back in the original position. To have an idea where they were read up:

http://wuarchive.wustl.edu/~aminet/h...A5001MChip.lha

this file has doco on howto have 1mb chip on rev5 and rev6, but also shows a diagram of the original position the jumpers are in.

If all else fails another good troubleshooting reference to look at is:

http://wuarchive.wustl.edu/~aminet/h...k/Amigafix.txt

Please keep us posted on how things are going! Cheers.

[1] jumpers described in 500hacks.txt, refer to section "v. Is My Jumper On The Line ?".

Amiga1992 · 02 October 2002, 07:10

Could also be a 500+ with half meg fucked up... but your badge would say "500 Plus"

Miggy2TheMax · 02 October 2002, 07:46

Quote:

Originally posted by Akira
Could also be a 500+ with half meg fucked up... but your badge would say "500 Plus"

That would have to be one hell of a wierd 500 Plus

Would the hi-res denise work ok with 1/2mb chup ?

Antiriad · 02 October 2002, 15:02

Its a B52/ROCK LOBSTER

Rev5 board. And is definitely a original A500.
Its got 512k RAM according to the board, but its got 16 little mem chips on it.

But it HAS got a Fatter Agnus, even tho the board just says Fat Agnus. Its

CSG
8372a
318069-02

So...does this mean I *should* have 1MB Chip Ram? But dont?
It didnt come with a Ram board in the trapdoor originally...

With the Fatter Agnus and the OS2.0, this is definitely sounding like a custom jobbie. Any ideas what could have gone wrong then?

Thx for the links, ill read em thoroughly...

RetroMan · 02 October 2002, 15:25

@Antiriad

Nope, you have 16 chips * 32 KByte = 512KByte

The possibillity of having 1 MB Chip on the Mobo was given for Board Revision 8 and above (or was it 6

) ....

Anyway, you possibly can use a mem expansion in the trapdoor as Chip Mem with that Fat Agnus

Antiriad · 02 October 2002, 16:43

Well, all seems ok in some ways. The JP2 pads have been re-ordered so that the top two pads have merged and the track between the bottom two cut.

Equally the _EXRAM line has been cut. But...both areas were both quite dirty due to it being a DIY job. Im wondering whether this dirt may be mucking things up. Ive attempted to clean up.Something ive noted is that the break is around Pin 6, rather than Pin 4 as recomended for the 1MB Chip Ram hack in the A5001 doc.

So maybe i can assume that whoever did this only intended Fat Agnus installation not the 1MB Chip Ram hack? I was amused to read that it would appear that the A501 ram isnt FAST but Slow despite the fact it registers as such. (This is correct???)

The Fatter Agnus installation is successful i guess, as according to Show Config i have ECS Agnus and ECS Denise. Im right that if this was an original A500 it would be OCS wouldnt it? I can go to 32 colours in Low Res mode.

Still, this still begs the question of what is wrong amongst these things and what can i do? I still cant get it to recognise the mem expansion in the trapdoor.

This is miffing as i need RAM in the particular address - $80000 to $C00000 or something, which only this can give to get a lot of Whdload slaves to work as they whinge at my 512k Chip Ram, but ignore my 4MB Fast Ram on my A500HD+ and the 4MB on the A5000 accelerator board which reside at other addresses.

BippyM · 02 October 2002, 17:25

The cut track was done to use the trapdoor expansion as chip ram, I seem to remember reading about it in an old Amiga mag. Have a look on the web

Antiriad · 02 October 2002, 19:49

Took another look at the 500hacks.txt, it doesnt seem to me that you HAVE to cut the _EXTRAM track to install the Fatter Agnus, it is only when you want to use the trapdoor expansion as chip ram.

As such, my A500 has had a botch job done on it. But which bit? The JP2 pads look correct. As previosuly stated, im wondering whether the position of the track break could have anything to do with it.

Im not sure whether its the fact he broke the track too far down that it doesnt work. But wouldnt this just keep the Mem Board as (False) FastRam rather than not have it work at all?

Maybe i should cut away the track further up beside Pin 4 as the A5001 doc specifically states?

I have noticed that the board doesnt seem to go *quite* as far across in as on my other A500, by a mm or so but this could be my paranoid imaginaton.

LUKas007 · 03 October 2002, 01:06

Anyway... A2000 rulez

Miggy2TheMax · 03 October 2002, 02:44

LUKas007, in your dreams 500 rules 4ever, don't let anyone tell you any different.

RetroMan, You can have 1mb on board from Rev 6. 500's are poWaFull

Antiriad, sounds like your 500 is a handful. I thought to use the ECS denise you need 1mb chip,wb 2.0 and Fat Agnus. So if you only have 1/2mb chip you shouldn't be able to get any of the ECS modes.

The best way to fix these problems is to use a _spare_ 500 that you mix and match the chips across. My starting point would be to swap the ECS denise for the OCS one and see if you get rid of all those gurus with 1/2mb chip. If you don't get gurus atleast you have stabilised the system. Then you can try the mem expansion in the trapdoor again and see if you can do the mod to get 1mb chip.

The 501 expansion is never really fast ram as it hangs of the address space that is used by the custom chips. It really only has two modes of operation.

1. slow ram - shows up as fast ram, but runs as slow as chip ram.

2. chip ram - shows up as chip ram and runs (you guessed it) at speed of chip ram.

anyhow, hope this helps, please keep us posted on your 500 adventures. Cheers.

RetroMan · 03 October 2002, 02:56

Quote:

Originally posted by Miggy2TheMax
RetroMan, You can have 1mb on board from Rev 6. 500's are poWaFull

As I said, I wasn´t quite sure on this one

Antiriad · 03 October 2002, 21:52

Well.... i do have a spare plain A500, but id rather leave it unmolested for now. As such, ive put my OS2 A500 back together again. Ill scour Ebay for some spare OCS chips, unless anyone here has any? At least i have its guruing explained now - thats very much appreciated.

It actually does calm down from the constant guruing after a few minutes, but ive never actually tried any ECS modes once it has. Methinks it would then f**k up if i did...

But with the A500HD+ attached it works fine - which it always is cos of its now 2GB hard drive in it

. Denise ECS seems to be happy to have memory from elsewhere. It is annoying the trap mem doesnt work, i wish i could force the A5000 mem to the address $80000...

LUKas007 · 03 October 2002, 23:00

Well... I have spare Denise 8362 (OCS) , Paula , CIA, and Agnus 8375

28 December 2002, 09:29

Well, I don't know if this helps at all,
but from my experience an A500, jumpered for
1 MB Chip needs a 512K Trapdoor Expansion wich
is deactivated(!) so it must be switchable and be turned off!
If it is turned on, the Machine will show a slowly
flashing yellow screen, and if there is no expansion
installed, it will crash as soon as anything is written in memory
between $80000 and $FFFFF bcause there is no memory
to write to, but the machine is set up that it "thinks" there is.
So you could solder switches both to the Chipram jumper
and the Expansion on/off jumper to use the Expansion
alternating as chip or "fake" fastram Expansion.
(Thats what I did)

Hope to help a bit and not missing the Subject...

01 October 2002, 22:03	#1
Antiriad The Sacred Armour Of Join Date: Aug 2002 Location: Sussex, UK Age: 44 Posts: 1,141	Cant memory expand my OS2 A500 Hello all, I bought a 500 about five years ago and have always been bemused by it. Its a 512k model with the old brown C= logo, but it has OS2.0. Now, can i assume that any A500s that came with OS2.0 were the A500+'s that had 1MB RAM and the new white C= badge? Therefore, assuming that the reason it has this is a custom jobby, can this explain why the f*er continually Gurus itself for several minutes after its booted up? Its only calm when i have the A500HD+ connected which adds 4MB Fast Ram. Does OS2 require 1MB to run??? The second thing is that the b***d wont accept any trapdoor upgrades that work perfectly well on my other A500. Could this be related? Any ideas would be appreciated. My principle prob is that id like more chip ram on it, but i suspect thats not possible without some soldering on the motherboard. Or buying a A500+ of course

02 October 2002, 15:02	#6
Antiriad The Sacred Armour Of Join Date: Aug 2002 Location: Sussex, UK Age: 44 Posts: 1,141	Its a B52/ROCK LOBSTER Rev5 board. And is definitely a original A500. Its got 512k RAM according to the board, but its got 16 little mem chips on it. But it HAS got a Fatter Agnus, even tho the board just says Fat Agnus. Its CSG 8372a 318069-02 So...does this mean I should have 1MB Chip Ram? But dont? It didnt come with a Ram board in the trapdoor originally... With the Fatter Agnus and the OS2.0, this is definitely sounding like a custom jobbie. Any ideas what could have gone wrong then? Thx for the links, ill read em thoroughly... Last edited by Antiriad; 02 October 2002 at 15:14.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Scalos on OS2?	Amiga1992	support.Apps	3	06 February 2011 12:39
Memory expansion for A500	source	support.Hardware	2	10 August 2009 21:54
A500+ with 1,5 MB Chip Memory	mombasajoe	support.WinUAE	5	08 May 2008 10:40
What systems would you like to expand?	BinoX	Amiga scene	9	03 July 2007 08:58
execbase os2,3+	bobbybearing	Coders. General	3	04 August 2006 22:04

01 October 2002, 22:08	#2
oldpx Posts: n/a	Your a5oo's original kickrom is replaced by a 2.0 one

02 October 2002, 05:32	#3
Miggy2TheMax Junior Member Join Date: Jan 2002 Location: Australia Age: 45 Posts: 381	sounds like its a stock 500 with 2.0 roms, like burseg says. Anyhow there could be a couple of reasons why the trapdoor expansion may not be working, I'd say the main reason would be because someone tried out a 1mb chip hack that went wrong. So I'd say you are going to have to open up your 500 and first identify what motherboard revision you got. If rev 5 read up the article below refer to section : "vii. 1Mb of Motherboard Memory on the Rev. 5" http://wuarchive.wustl.edu/~aminet/h...k/500hacks.txt If rev 6 then your jumpers[1] are out of wack cos someone tried a hardware hack that went wrong and forgot to put the jumpers back in the original position. To have an idea where they were read up: http://wuarchive.wustl.edu/~aminet/h...A5001MChip.lha this file has doco on howto have 1mb chip on rev5 and rev6, but also shows a diagram of the original position the jumpers are in. If all else fails another good troubleshooting reference to look at is: http://wuarchive.wustl.edu/~aminet/h...k/Amigafix.txt Please keep us posted on how things are going! Cheers. [1] jumpers described in 500hacks.txt, refer to section "v. Is My Jumper On The Line ?".

02 October 2002, 07:10	#4
Amiga1992 Registered User Join Date: May 2001 Location: ? Posts: 19,645	Could also be a 500+ with half meg fucked up... but your badge would say "500 Plus"

02 October 2002, 15:25	#7
RetroMan Registered User Join Date: Aug 2001 Location: Germany Age: 51 Posts: 3,704	@Antiriad Nope, you have 16 chips * 32 KByte = 512KByte The possibillity of having 1 MB Chip on the Mobo was given for Board Revision 8 and above (or was it 6 ) .... Anyway, you possibly can use a mem expansion in the trapdoor as Chip Mem with that Fat Agnus

02 October 2002, 16:43	#8
Antiriad The Sacred Armour Of Join Date: Aug 2002 Location: Sussex, UK Age: 44 Posts: 1,141	Well, all seems ok in some ways. The JP2 pads have been re-ordered so that the top two pads have merged and the track between the bottom two cut. Equally the _EXRAM line has been cut. But...both areas were both quite dirty due to it being a DIY job. Im wondering whether this dirt may be mucking things up. Ive attempted to clean up.Something ive noted is that the break is around Pin 6, rather than Pin 4 as recomended for the 1MB Chip Ram hack in the A5001 doc. So maybe i can assume that whoever did this only intended Fat Agnus installation not the 1MB Chip Ram hack? I was amused to read that it would appear that the A501 ram isnt FAST but Slow despite the fact it registers as such. (This is correct???) The Fatter Agnus installation is successful i guess, as according to Show Config i have ECS Agnus and ECS Denise. Im right that if this was an original A500 it would be OCS wouldnt it? I can go to 32 colours in Low Res mode. Still, this still begs the question of what is wrong amongst these things and what can i do? I still cant get it to recognise the mem expansion in the trapdoor. This is miffing as i need RAM in the particular address - $80000 to $C00000 or something, which only this can give to get a lot of Whdload slaves to work as they whinge at my 512k Chip Ram, but ignore my 4MB Fast Ram on my A500HD+ and the 4MB on the A5000 accelerator board which reside at other addresses.

02 October 2002, 17:25	#9
BippyM Global Moderator Join Date: Nov 2001 Location: Derby, UK Age: 48 Posts: 9,355	The cut track was done to use the trapdoor expansion as chip ram, I seem to remember reading about it in an old Amiga mag. Have a look on the web

02 October 2002, 19:49	#10
Antiriad The Sacred Armour Of Join Date: Aug 2002 Location: Sussex, UK Age: 44 Posts: 1,141	Took another look at the 500hacks.txt, it doesnt seem to me that you HAVE to cut the _EXTRAM track to install the Fatter Agnus, it is only when you want to use the trapdoor expansion as chip ram. As such, my A500 has had a botch job done on it. But which bit? The JP2 pads look correct. As previosuly stated, im wondering whether the position of the track break could have anything to do with it. Im not sure whether its the fact he broke the track too far down that it doesnt work. But wouldnt this just keep the Mem Board as (False) FastRam rather than not have it work at all? Maybe i should cut away the track further up beside Pin 4 as the A5001 doc specifically states? I have noticed that the board doesnt seem to go quite as far across in as on my other A500, by a mm or so but this could be my paranoid imaginaton.

03 October 2002, 01:06	#11
LUKas007 Registered User Join Date: May 2002 Location: England Age: 45 Posts: 159	Anyway... A2000 rulez

03 October 2002, 02:44	#12
Miggy2TheMax Junior Member Join Date: Jan 2002 Location: Australia Age: 45 Posts: 381	LUKas007, in your dreams 500 rules 4ever, don't let anyone tell you any different. RetroMan, You can have 1mb on board from Rev 6. 500's are poWaFull Antiriad, sounds like your 500 is a handful. I thought to use the ECS denise you need 1mb chip,wb 2.0 and Fat Agnus. So if you only have 1/2mb chip you shouldn't be able to get any of the ECS modes. The best way to fix these problems is to use a _spare_ 500 that you mix and match the chips across. My starting point would be to swap the ECS denise for the OCS one and see if you get rid of all those gurus with 1/2mb chip. If you don't get gurus atleast you have stabilised the system. Then you can try the mem expansion in the trapdoor again and see if you can do the mod to get 1mb chip. The 501 expansion is never really fast ram as it hangs of the address space that is used by the custom chips. It really only has two modes of operation. 1. slow ram - shows up as fast ram, but runs as slow as chip ram. 2. chip ram - shows up as chip ram and runs (you guessed it) at speed of chip ram. anyhow, hope this helps, please keep us posted on your 500 adventures. Cheers.

03 October 2002, 21:52	#14
Antiriad The Sacred Armour Of Join Date: Aug 2002 Location: Sussex, UK Age: 44 Posts: 1,141	Well.... i do have a spare plain A500, but id rather leave it unmolested for now. As such, ive put my OS2 A500 back together again. Ill scour Ebay for some spare OCS chips, unless anyone here has any? At least i have its guruing explained now - thats very much appreciated. It actually does calm down from the constant guruing after a few minutes, but ive never actually tried any ECS modes once it has. Methinks it would then f**k up if i did... But with the A500HD+ attached it works fine - which it always is cos of its now 2GB hard drive in it . Denise ECS seems to be happy to have memory from elsewhere. It is annoying the trap mem doesnt work, i wish i could force the A5000 mem to the address $80000...

03 October 2002, 23:00	#15
LUKas007 Registered User Join Date: May 2002 Location: England Age: 45 Posts: 159	Well... I have spare Denise 8362 (OCS) , Paula , CIA, and Agnus 8375

28 December 2002, 09:29	#16
G.S. Posts: n/a	Well, I don't know if this helps at all, but from my experience an A500, jumpered for 1 MB Chip needs a 512K Trapdoor Expansion wich is deactivated(!) so it must be switchable and be turned off! If it is turned on, the Machine will show a slowly flashing yellow screen, and if there is no expansion installed, it will crash as soon as anything is written in memory between $80000 and $FFFFF bcause there is no memory to write to, but the machine is set up that it "thinks" there is. So you could solder switches both to the Chipram jumper and the Expansion on/off jumper to use the Expansion alternating as chip or "fake" fastram Expansion. (Thats what I did) Hope to help a bit and not missing the Subject...

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)