| Title: | AMIGA NOTES |
| Notice: | Join us in the *NEW* conference - HYDRA::AMIGA_V2 |
| Moderator: | HYDRA::MOORE |
| Created: | Sat Apr 26 1986 |
| Last Modified: | Wed Feb 05 1992 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 5378 |
| Total number of notes: | 38326 |
I am planning to build a memory expansion by my own , and as i found
out looking around through all the notes , it seems everybody is
only buing ready assembled ones.
When I'am looking at the A 500 drawings , it looks like Agnus will
only handle a total of 1 Meg.
Second , looking at German Magazines for cheap expansions , bare
bords etc. I found some , but not cheap .....
For Example Gigatron 2 Meg. Bare bord which fits into the A500 s
Memory extension slot costs 228 DM which is ca. 150 $.
but ..= you must use 1 Meg Chips and you can only use 1.8 Meg of
the bord for getting a total of 2.3 Meg.
Well , i saw the drawings and found out they put gary on an extension
socket with an integrated PAL to generate A9 to the Chips.
Looks ok . but 1 Meg Chips are very very expensive here in Germany
so I don't wanna loose 256K for use.
Having a couple of 256K 150nS Chips from older Projects available
, is there anybody which can offer me a drawing for Mem.Exp. using
256 K Rams???
Or any help to design it ?
Another thing is , yesterday evening i tryed to change the jumper
JP 2 on Ami Motherboard to change Memory expansion Ram Mapping
Adress from a23 #C00000 to A19 080000 , but system would not come
up ( white screen , Power led flashing ).
Reset to Original setting all ok.
The reason was , starting Mem.Ex with A19 should allow me to build
an easier decoder logic around agnus to select several Banks of
256K chips to get ( by the help of A20/21/22 ) a total of 4 Meg.
Any hints are very welcome.
Kind regards Ingo
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 2300.1 | JP 2 reserved for future product | LEVERS::PLOUFF | Semipro Semiologist | Wed Mar 01 1989 12:30 | 17 |
Re: changing the internal address decoding jumper.
> Another thing is , yesterday evening i tryed to change the jumper
> JP 2 on Ami Motherboard to change Memory expansion Ram Mapping
> Adress from a23 #C00000 to A19 080000 , but system would not come
> up ( white screen , Power led flashing ).
> Reset to Original setting all ok.
This problem was discussed on Usenet. If you change the jumper, then
the operating system thinks you have one megabyte of chip RAM, i.e. the
RAM used by the graphics chips. But the graphics chips in your machine
are most likely the version that can only address 512K. So memory will
be used in a way the hardware cannot handle, and the machine will
crash.
Moral: don't move the jumper until you install the new chip set
(not yet widely available, anyway).
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