NMS8220 Discharge RAM memory faster at powercycle.

Hero (572)

24-01-2012, 08:30

Hello.

My internal DRAM doesn't really discharge very fast on my NMS8220. When loading a .rom file with "AB" still in the &h4000 and &h4001 adress and a powercycle it needs to be turned off for like 3 minutes or longer. I could remove the "AB" but for future experiments this could be annyoning.

I heared Jan of nowind talk about a capacitor hardware patch for this problem at nijmegen. Anyone a how to? I did a search first ;-)

Thanks!

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Van RetroTechie

Paragon (1563)

24-01-2012, 08:53

Even if you could find a hardware fix to reduce this problem, why make a hardware problem out of a silly software issue?

A hex editor (eg. DiskView 2) is your friend... For 'future experiments' there's emulators, Flash carts, and in a pinch you can always edit the "AB" back in (I used to overwrite just the "A" with a 0 byte, makes it easy to find that location in a .bin loader if necessary later).

Van Wlcracks

Hero (572)

24-01-2012, 09:32

... but for future experiments this could be annyoning.

and here comes a spoiler. A nms8220 doesnt have a diskdrive. I use caslink2 now through ipad.

Van Manuel

Ascended (19678)

24-01-2012, 21:17

Lol!

Van Wlcracks

Hero (572)

03-03-2017, 17:28

So anyone has figured this out how to fix this in hardware, in the past 5 years? I recon other systems have this problem too?
I have dusted off the 8220, now with philips diskdrive with sd card replacement drive (hxc), but sometimes you have to turn the msx off for 5 minutes until the ram has cleared.

Van Jipe

Paragon (1625)

03-03-2017, 18:13

for solving this problem in past i find many ROMS of games with 42 41 "BA" at start

Van sd_snatcher

Prophet (3675)

03-03-2017, 21:46

Tip: Execrom removes the AB signature by default. There's an option to preserve it when you need.

Van Wlcracks

Hero (572)

04-03-2017, 06:07

Thanks all but i was searching for a hardware solution.

Van Louthrax

Prophet (2496)

04-03-2017, 11:36

Wlcracks wrote:

Thanks all but i was searching for a hardware solution.

Replacing the RAM chips ? Unless there's some "residual current" when the MSX is powered off... (but I doubt that).

Van RetroTechie

Paragon (1563)

04-03-2017, 19:43

DRAM essentially is an array of tiny capacitors. So it isn't that strange some of that charge keeps hanging on. You might say your DRAM works too well in this case...

If you 'have' to have a hardware fix: how about a modified BIOS ROM that does a destructive RAM search at boot? MSX2+ does this, maybe there's some ROMs for Philips regular MSX2's out there that do the same? And the NMS8220 has some built-in firmware. If that's socketed, should be easy to add-in a ROM that nukes RAM-held "AB" signatures and such.

Van Louthrax

Prophet (2496)

04-03-2017, 20:05

RetroTechie wrote:

If you 'have' to have a hardware fix: how about a modified BIOS ROM that does a destructive RAM search at boot?

Wouldn't that be a software fix ?