Conference hydra::amiga_v1

Re: .0

I don't know much about the A500 (most of my knowledge is about the B2000).
I'll kick in my $.02 and see if anyone can expand upon it or set me straight.

>1. I was suprised to find only four DRAM chips inside (OKI M514256-12)
>   Does this mean thses chips are 256k x 4 Bits ?
>   The schematics in the back op the Amiga 500 manual show 256k x 1bit
>   chips x 16 . 
>
>2. Does this mean the schematics in the manual are out of date with the
>   machine.  If so are there any other significant differences.

I wouldn't be surprised if the Commodore has changed the memory chips
since most manufactures left the 256k x 1 market.  I suspect you are
right.

I'd suspect that any changes would simply be there to decrease manufacturing
costs.  But then, there are those four empty sockets.

>3. There are four empty DRAM sockets in the machine . I pressume these take
>the machine to 1Mb chip memory when installed .

The B2000 comes with 1 meg of memory on the motherboard.  On early revisions
of the B2000, a jumper controls whether that memory was one meg of chip
memory or 512K chip/512K half-fast.  (Later revisions have removed the
jumper in order to have manufacturing costs.  After installing the new
graphics chips in the newer B2000s, you cut a trace on the mother board
to enable one meg of chip memory.)

I've always assumed that the A500 was similar, and the A501 512K/clock
upgrade module contained what would be the other 512K of chip memory
once the new graphics chips were installed.

Furthermore, Agnus "manages" all 1 meg of memory on the B2000 motherboard.
I thought it did the same for the A501 memory.  Thus, unless the new
Agnus services all 1.5 meg of memory, those four empty sockets are
going to conflict with the A501 memory.

Where there any empty sockets on the early rev A500s?  If not, it would
seem to indicate the A501 memory is supposed to be the other 512K of
the one meg chip memory.

I wonder if Commodore is going to go to 1 meg of memory on the motherboard
for A500s standard, and are going to discontinue the A501?  If so, your Amiga
500 may be some intermediate revision (until all the A501s are sold, probably).

>  From what I can understand
>   from this notes file the present graphic chips would not be able to access
>   this memory if it were installed .But if I installed it would it be of ANY
>   advantage ie. would it be used for storeing programs etc.

A B2000 can't boot if you set the jumper to make it have one meg chip ram.


>5. Do the third party memory boards for the amiga (I'm talking about the big
>   >1meg boards) use the agnes chip for RAS and CAS signals or do they 
>   generate their own. 

They are on their own.


>6. When you see memeory boards advertised and the say 1Mb . Do they "generally"
>   mean this brings the machine up to 1Mb or that the expansion contains 1Mb ?

I've seen very confusing ads about this.  Some of the third party A501
clones list the amount of memory in your system after you install it
(a one meg upgrade!), instead of telling you how much memory is on the
board (512k).  You have to read the ad carefully to discover which.

    To complement Randy's reply:
    
    Could tell us what is scribbled on the Fat Agnus? You may already
    have one that can address 1MB of ChipMemory. 
    
    And it will be either the internal upgrade (I'd go for that, 4 chips
    should be cheaper) or the A501, since even the "Obese" Agnus can
    only address one Meg.
    
    I'll try to get my hands on the upgrade notes at CBM Frankfurt (they
    are located just 800m away from here (FRN)). If I find out anything,
    I'll let you know.
    
    -	<CB>
    

    
    I'll open her up again over the weekend and have a look to see what
    the numers on fat Agnes are.
    
    The memory was inserted into U19,18,17 & 16 but not in U20,21,22
    or 23 .Just abouve this written on the board was 500K/1Mb ...
    
    Also , from what I remember there is a  modification to one of the
    two 74F244 memory bus driver chips. I think it is U35 , It has a
    little board with about three chips on it , inserted upside down
    where U35 should be , there is also a black "ECO" wire running
    from this board to the system board. 
    
    If I can get my hands on these chips i'll stick em in .They do seem
    a bit unusual though ,I got plenty 256k x 1 or could get 1Mb x 1
    but I've never seen 256k x 4 ...
    
    Steve..
    
    Thanx for the info.
     

    The 256*4 chips aren't that unusual, CBM used them for some time
    know. I suspect other manufacturers also use 'em, because they're
    just so practical. You can have smaller memory increments, it takes
    two 256*4 to get you 256KB, but you'll need 8 1Mb chips to get an
    eight bit wide bus.
    Anyway, they should be readily available.
    BTW, the chances that you might have an "Obese" Agnus are increasing,
    since I just learned the the 6.1 rev of the B2000 board comes with
    them already installed, but still configured for 512KB.
    
    Oh, and I forgot to warn you about any Mem boards >512KB inside
    the A500. Since these boards don't use the autoconfiguring protocol
    to register their memory with the system they have to use fixed
    addresses. These are just bound to collide with something like an
    A590 that you might wanna attach to your expansion bus in the future.
    
    -	<CB>
    

Re: .4

>You can have smaller memory increments, it takes two 256*4 to get
>you 256KB, but you'll need 8 1Mb chips to get an eight bit wide bus.

Actually, it is worse than that.  The Amiga has a 16 bit wide bus, so
if you use 1m x 1 chips, you must use 16 for a minimum configuration
of 2 megabytes.  (Way back in this notesfile I made some prediction that
Commodore would go to 1m x 1 chips in the future.  It sounded good
until someone pointed out the 16 bit wide bus to me.)

>BTW, the chances that you might have an "Obese" Agnus are increasing,
>since I just learned the the 6.1 rev of the B2000 board comes with
>them already installed, but still configured for 512KB.

I was watching "Computer Chronicles" last night on TV, and in their
news segment they reported:

	"Commodore has released a new Agnus chip for their Amiga line
	of computers.  The new chip corrects a problem [sic] with
	addressing graphics memory and allows one meg to be used
	just for graphics."

Jeeze, "corrects a problem."  Yeah, "Intel announced a new 80486
microprocessor that corrects a problem with the execution speed
of the 80386."

    
    
    The numbers on the Fat Agnus gate array are 
    
            MOS 8371
    		3488 21
    
    Any one know if this a new one with the 1MB address capability ?

    
    Also , over the weekend I got my home made A501 512k mem expansion
    working. The problem was I used these 2 sip modules that are 256k
    x 9 . I wired the data pins to arbitrary data pins on the connector
    which was no good because each byte has its own CAS line and when
    one was enabled it should use the upper or lower 8 bits but not
    bits from either . Anyway when I realised what I'd done and put
    it right it worked great .
    I tried it out by running Falcon and I could now use the
    black box option in the game and I got to hear the sounds that 
    only 1meg amiga owners get to hear ...
        
    Also I've found a source for the 256k x 4bit memory chips so I'll
    stick in four of them next weekend . If the Anus <del> <del> agnus
    chip adresses them and  I  can get 1meg chip mem ,well and good
    but if it  can't I'll settle for a 1meg internal upgrade .
    
    
    Steve..
    
    
    
    
    
    

    
      I'm thinking about getting a 2000.  I would like to upgrade the
    memory to 2 meg or more using some old 256K chips from the Rainbow
    memory boards.  Can this be done ?  What board will I need to buy?
    How many chips will be needed for each meg ?
    
    Thanks  Bob
    

>      I'm thinking about getting a 2000.  I would like to upgrade the
>        memory to 2 meg or more using some old 256K chips from the Rainbow
>    memory boards.  Can this be done ?  What board will I need to buy?
>    How many chips will be needed for each meg ?

 
    Well, I am in the process of doing this with my 1000.  I bought
    the chips from DECDirect (2 sets of 9 each) for about $57 per set.
    You'll need 16 chips.  As for board, I bought a Starboard II to
    put on the side.  I was a bit wary that it wouldn't work, but it
    all tested fine.  Unfortunately, it seem the Starboard itself is
    bad. I sent it back to Microbotics and they are looking at it.
    (Don't you hate those problems where everyone says, "It SHOULD work,
    I don't know why it doesn't.")

    You need chips that are rated at 150 ns (nano-sec) or faster (120
    ns, 100 ns...), the Rainbow only needed 200 ns devices, and these
    are useless.  Some did come with the right chips that you need,
    but I don't think that DECdirect ships those, and at $57/9.
                                                             
    Jean
    

    I bought a MEGAboard 2000 (made by ASDG) and sold thru Progressive
    Peripherals & Software. It was US$225 for a 0K board. I have populated
    it with 64x256 chips from Rainbows etc (these were all 120ns versions)
    and it works fine (well i have problems with it and my 2090A, but it
    seems to be a 68000 problem - i think note #2479). It runs the
    diagnostics and with the 2 floppies i don't have any problems. It can
    be populated with 512k (16 chips) or 1M (32 chips) or 2M (64 chips) and
    is jumper selectable. It is autoconfiguring. I thought about using the
    8-UP board, but Microbotics told me that noone makes an unpopulated
    SIMM module for the 256k chips, so i ruled it out. I mailordered it and
    it was at my door in 7 days (in Canada even). 
    
     mark

    
       Thanks,  Just the info I needed and wanted to hear.
    
    - Bob -
    

    Re: .6
    
    Sorry pal, you got an ole one.
    
    The obese Agnus is labeled 8372 etc....
    
    At least you know now for sure.
    
    -	<CB>
    

           <<< LNKUGL::DUA1:[NOTES$LIBRARY]APPLE_COMPUTERS.NOTE;2 >>>
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================================================================================
Note 668.11                   Memory compatibility                      11 of 11
DNEAST::GREVE_STEVE "If all else fails, take a nap." 26 lines  13-APR-1989 14:13
                        -< Thanks for the memories... >-
--------------------------------------------------------------------------------
    	Boy, I was just about to go into a serious "pout"!!!  I called
    our EPP and was told that all our rainbow 256k chip sets were gone!
     Drat... that was 9 chips for 56.11.... anyway.. the fellow there
    gave the the following info:
    
    Mocroprocessor Unlimited
    24000 So Peoria Ave
    Beggs, OK. 74421
    918-267-4961
    
    
    	I called these nice folks and they have Samsung and Hitachi
    256k by 1, dram, 150ns, cas before ras refresh for $58 a set (8).
     To have an order shipped to you the cost is $62.05 a set.   The
    hitachi part number I was given was HM50256p-15.  I guess I'll send
    away for a coupla sets and see how they work... anyone know if this
    part number is in the AE "OK to use" list???
    
    
    Steve