Author Topic: Wanted - Re-Implementation of Retro RAM Expansion, 512 KB Min. / DKtronics  (Read 769 times)

0 Members and 1 Guest are viewing this topic.

Offline LambdaMikel

  • Supporter
  • 6128 Plus
  • *
  • Posts: 763
  • Country: us
    • Homepage
  • Liked: 354
... I know, there is XMem (works), ZMem, 4 MB Piotr / Zaxon.... and another 512 KB expansion from Piotr / Zaxon as well. I own them all. However, because I encountered numerous problems with these newer expansions (XMem being the exception, the only expansion that works like a charm on my 464!) I would really like to see a 100% compatible re-implementation of the existing DKtronics designs, with old RAM chips and GAL22V10 selection logic or the like to get accurate and reliable timing. There are numerous problems I think with the newer extensions unfortunately. Any pointers / existing project to get this project going?

Offline rpalmer

  • 464 Plus
  • *****
  • Posts: 495
  • Country: au
  • Liked: 331
LambdaMikel,I am still working on a memory expansion which uses simple ICs like the PAL chips and logic ICs rather than FPGA or similar.
It is currently in 2 parts the MMU and the memory module. The MMU has the PAL and logic gates while the memory module is simply just the RAM chips and maybe a decoder for address to SRAM chip select.

rpalmer

Offline LambdaMikel

  • Supporter
  • 6128 Plus
  • *
  • Posts: 763
  • Country: us
    • Homepage
  • Liked: 354
That'll be great  :)

Offline Vyper68

  • Supporter
  • CPC6128
  • *
  • Posts: 230
  • Country: gb
  • 8-Bit Forever! - You know it makes sense
    • index.php?action=treasury
  • Liked: 94
That'll be great  :)

I second that. I have wanted to get a RAM expansion for a while now some i can run so of the modern operating systems. There seems to be teething problems with a few which made me want to go "old Skool" and get a DK Tronics RAM Pak but they rarely surface. So a new 100% compatible version would be really welcome.
Paul Woakes - Genius & Programmer

Thank you for Mercenary Paul

Offline rpalmer

  • 464 Plus
  • *****
  • Posts: 495
  • Country: au
  • Liked: 331
attached is the first prototype MMU and memory module to expand the CPC.

The memory module can be up to 64MB (yes you read right 64 Megabytes and is no mistake).

I have to get the PCB re-done, since I missed the "EXTRAM_EN" signal to the memory bus. This meant the MMU would switch in the external memory all the time and lock up the CPC.

rpalmer

Offline rpalmer

  • 464 Plus
  • *****
  • Posts: 495
  • Country: au
  • Liked: 331
attached is how I manage to get 64MB from the MMU.

Offline GUNHED

  • 6128 Plus
  • ******
  • Posts: 587
  • Country: de
  • Reincarnation of TFM
  • Liked: 267
Great news. However, it would be an advantage to stay compatible to the 4 MB standard via &7Fxx...&78xx.  :) :)
« Last Edit: 20:04, 05 April 18 by GUNHED »
http://futureos.de --> Get the revolutionary FutureOS (Recent update: 2018.08.23)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Ver.: 2018.08.15)

Offline rpalmer

  • 464 Plus
  • *****
  • Posts: 495
  • Country: au
  • Liked: 331
GUNHED

It does stay compatible as it uses the address memory address twice to get more.

The 4MB expansion by people like Yarek use I/O address bit A10 to A8 to get the 4 MB address space (8 x 512K), I use only A9 to A8 to get 2MB (4 x 512K). I then use configuration zero to get 5 more bits of the memory bus and voila 32 x 2 MB.

So if people want to use just the one address for memory expansion, then the memory module can simply ignore the upper 5 bits of the memory bus and get just 2 megabytes.

rpalmer

Offline ComSoft6128

  • ..................................
  • Supporter
  • 6128 Plus
  • *
  • Posts: 642
  • Country: scotland
  • CPC THEN CPC NOW
    • index.php?action=treasury
  • Liked: 573
Is there any software that could use this?

Cheers,

Peter

Offline rpalmer

  • 464 Plus
  • *****
  • Posts: 495
  • Country: au
  • Liked: 331
For the standard 2 Mb the answer would be yes for what has been developed so far (obviously limited to 2 MB), but as for the higher capacity then it is no at the present as I have yet to get even the prototype finished (i have already got the new board on order from beta layout and if successful will source them from someone else at significant reduced cost). I have recently seen that JLC PCB (from a youtube video) has an offer for PCB production of 10 boards for $2 (US) and i don't know how long that will last of even if it just the first order only.

However, as more people see that having much larger capacity to work with is a bonus then we may see programs like SYMBOS, FutureOS and maybe others use it as they see fit.

I would also like to point out that to get more than 8Mb would see costs rise dramatically since chips with higher capacity are more costly.
The current source for 2MB SRAM chips is about $35AUS per chip from E14 and to make 16MB would need 8 chips which cost about $280 just for the memory (ouch). The 8 MB module uses 1MB SRAM chips which are 5 EURO each (from reichelt) and so 8MB is just 40 EURO (about $60AUS).

rpalmer

Offline Vyper68

  • Supporter
  • CPC6128
  • *
  • Posts: 230
  • Country: gb
  • 8-Bit Forever! - You know it makes sense
    • index.php?action=treasury
  • Liked: 94
For the standard 2 Mb the answer would be yes for what has been developed so far (obviously limited to 2 MB), but as for the higher capacity then it is no at the present as I have yet to get even the prototype finished (i have already got the new board on order from beta layout and if successful will source them from someone else at significant reduced cost). I have recently seen that JLC PCB (from a youtube video) has an offer for PCB production of 10 boards for $2 (US) and i don't know how long that will last of even if it just the first order only.

However, as more people see that having much larger capacity to work with is a bonus then we may see programs like SYMBOS, FutureOS and maybe others use it as they see fit.

I would also like to point out that to get more than 8Mb would see costs rise dramatically since chips with higher capacity are more costly.
The current source for 2MB SRAM chips is about $35AUS per chip from E14 and to make 16MB would need 8 chips which cost about $280 just for the memory (ouch). The 8 MB module uses 1MB SRAM chips which are 5 EURO each (from reichelt) and so 8MB is just 40 EURO (about $60AUS).

rpalmer

Looks like 8MB is the sweet spot as far as production and peoples wallets are concerned and 8MB should be plenty big enough to be honest. When can i order one please  ;D
Paul Woakes - Genius & Programmer

Thank you for Mercenary Paul

Offline Chinnery

  • CPC664
  • ***
  • Posts: 106
  • Country: gb
  • Liked: 55
I have recently seen that JLC PCB (from a youtube video) has an offer for PCB production of 10 boards for $2 (US) and i don't know how long that will last of even if it just the first order only.
I have used them a few times, and it has always been $2 for 10 proto boards + shipping.
They did at one time offer free DHL shipping on your first order which I did a few times using different email/paypal/delivery addresses but I now stick with normal snail mail which makes the order around $10 for 10 boards.

Offline GUNHED

  • 6128 Plus
  • ******
  • Posts: 587
  • Country: de
  • Reincarnation of TFM
  • Liked: 267
GUNHED

It does stay compatible as it uses the address memory address twice to get more.

The 4MB expansion by people like Yarek use I/O address bit A10 to A8 to get the 4 MB address space (8 x 512K), I use only A9 to A8 to get 2MB (4 x 512K). I then use configuration zero to get 5 more bits of the memory bus and voila 32 x 2 MB.

So if people want to use just the one address for memory expansion, then the memory module can simply ignore the upper 5 bits of the memory bus and get just 2 megabytes.

rpalmer


Yes, that's what I got from you documents too. Thanks for the clarification. Well, of course it would be really nice to have all 4 MB compatible. But 2 MB compatible is for sure a great thing. And up to now few software needs more RAM anyway. I don't know it it would be hard to add an "switch" for 4 MB compatibility, but of course 2 MB is fine too :-)

http://futureos.de --> Get the revolutionary FutureOS (Recent update: 2018.08.23)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Ver.: 2018.08.15)

Offline GUNHED

  • 6128 Plus
  • ******
  • Posts: 587
  • Country: de
  • Reincarnation of TFM
  • Liked: 267
Is there any software that could use this?

Cheers,

Peter


A while ago Jarek released the first 4 MB expansion and there is a second now. I did some software supporting 4 MB: A 4 MB demo showing the intro of Captain Future. Two games (in development still).
A bit more software is using 1 MB RAM, f.e. Bad Apple from Shining. And relatively "lots" of software is using 512 KB.  :)


EDIT: About 20 years ago RAM7 and me talked about RAM expansions, back the day it was 2 MB and he had the great idea to use blocks of 512 KB.
Every block can be selected due to the high-byte: &7Fxx, &7Exx, ... &78xx. Every one can control 512 KB. So using highbytes from &78xx...&7Fxx gives 4 MB RAM.


Going lower that &78xx will produce compatibility problems. Some hardware (I got here) already makes problems when using 4 MB RAM, since some expansions are not fully decoded - sadly.

« Last Edit: 15:31, 06 April 18 by GUNHED »
http://futureos.de --> Get the revolutionary FutureOS (Recent update: 2018.08.23)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Ver.: 2018.08.15)