68040 40Mhz Upgrade on Milan

All things related to the Hades and Milan clones

Moderators: Mug UK, moondog/.tSCc., [ProToS], lp, Moderator Team

medmed
Retro freak
Retro freak
Posts: 16
Joined: Sat Apr 02, 2011 5:06 am
Location: France, Paris

68040 40Mhz Upgrade on Milan

Postby medmed » Sat Aug 03, 2013 9:47 pm

Hi,

I have a 68040 who can run at 40Mhz and a Milan with a 68040 clocked to 25Mhz.

I'm thinking to swap the original cpu by the 40Mhz but i've read the following warning from this link: http://www.der-ingo.de/en/milanhelp/hardware.html

If you want to run you Milan with more than 25 MHz properly, you'll need one very special chip, which is very hard to find. It is the chip 74ACT157 SO16, small version


I've searched what this IC do (found this link http://www.fairchildsemi.com/ds/74/74ACT157.pdf) but i already don't understand why we need this to change the clock of a cpu.

If someone can help me and sorry for my bad english.

Many thanks.
M.Medour - 1040STF, Mega STE + Spektrum card, Milan 040 + S3Video + ES1371.

rpineau
Captain Atari
Captain Atari
Posts: 489
Joined: Wed Jun 29, 2011 6:39 am
Location: California / USA
Contact:

Re: 68040 40Mhz Upgrade on Milan

Postby rpineau » Sat Aug 03, 2013 10:09 pm

It's a component response time issue. If you increase the frequency, the component need to react at least as fast as a clock cycle, sometimes faster.
The 74ACTxxx family as a response time of 7.5 to 9.5 ns.
If you can't find them I'll recommend the 74FCT157 as it has a response time of 4.3 ns at 5v which is even faster than the 74ACT157.
the 74FTC157 in SOIC-16 package is easy to find (mouser is a good source if you're in USA) and is cheap ( mouser has it for $1.72).

Regards,
Rodolphe
Falcon + AB040 + Eclipse PCI + ATI Rage VGA card + NE2000 Ethernec + HxC Floppy Emulator
MegaSTE 4MB + CosmosEx / 1040 STF for hardware dev
http://www.rti-zone.org/atari.php

medmed
Retro freak
Retro freak
Posts: 16
Joined: Sat Apr 02, 2011 5:06 am
Location: France, Paris

Re: 68040 40Mhz Upgrade on Milan

Postby medmed » Sun Aug 04, 2013 12:09 am

I hoped to make my milan more powerful without make the 060 adapter by just replacing the 040.

It seems that to make the milan most powerful we can't pass through.

I'll see with the shematics on the web and I think I'll reopen new topic to understand what I do :)

Thank you very much.
M.Medour - 1040STF, Mega STE + Spektrum card, Milan 040 + S3Video + ES1371.

Rustynutt
Captain Atari
Captain Atari
Posts: 201
Joined: Wed Mar 21, 2012 7:38 am
Location: Oregon
Contact:

Re: 68040 40Mhz Upgrade on Milan

Postby Rustynutt » Mon Oct 14, 2013 5:36 am

When working on the Milan, it is easy to forget to power off before swapping keyboard connector.
This scared me one night! Reading about other motherboards helped me trace down a problem I had when the keyboard stopped working.
From the keyboard connector to the control chip, there is a place where the trace where it makes a tight turn. The material is very very thin at that point, and swapping the keyboard out with power to the board can cause this to burn easily. Very small amperage, I repaired the trace, installing a fuze would be the best protection.

My Milan is boxed up ATM, if anyone has this problem, or wishes to put information into their note book, will take time to locate the circuit.

Good luck replacing the slower chips. This is a project I wish to do as well in the future. I have clocked my Milan at 33MHz, but no faster. It is much more stable at 25MHz, which is a waste of a good machine :).


Social Media

     

Return to “Hades / Milan”

Who is online

Users browsing this forum: No registered users and 1 guest