ericmcg@pro-generic.cts.COM (Eric Mcgillicuddy) (11/22/89)
The power supply has a 12V line in addition to +-5V lines. I have a //c so I don't know if it comes to the slots, I assume it does. (STD cards support it so one assumes Apple does) Two resistors of equal value can be used as a voltage divider, one between ground and Vdd and the other between Vdd and +12V. The 65816 require 4mA/MHz, so 40mA are required for 10Mhz. The resistors shoould be fairly small around 150 ohms to supply the current. Also the power trace needs to be cut on the card. I take no responsibility for any damages that may result from implimenting this information. I personally do not think it is worth voiding the warranty for 15-20% increase in speed. BTW make sure you have a good fan, the heat dissipation morre than doubles at this speed and the chips is more susceptible to heat variations when 'pushed'.
sb@pro-generic.cts.COM (Stephen Brown) (11/27/89)
In-Reply-To: message from ames!ucsd!pro-generic.cts.com!ericmcg@apple.com I'm afraid that I wouldn't use a simple resistive divider to obtain my 6volts from the 12 volts. A solid state regulator (such as the 7806) has better line and load regulation. At 40 mA it would be dissipating around 1/4 watt... not too bad, and with a couple of tantalum capacitors, it would beat your resistive divider hands down. Of course, it would cost more, but you just can't afford to have voltage fluctuations in a CPU circuit. I don't (yet) have a TWGS, but I think it would be worth the increase in speed to go for a faster 65816. Sure, at some point the increase in speed becomes ridiculous... BUT I WANT RIDICULOUS! Sorry, just wasting bandwidth again.. Bad sb, bad sb. ------------------------------------------ ProLine: sb@pro-generic ARPA: crash!pnet01!pro-generic!sb@nosc.mil INET: sb@pro-generic.cts.com UUCP: crash!pnet01!pro-generic!sb ------------------------------------------ You don't flame on me, and I don't flame on you. UUCP: crash!pro-generic!sb ARPA: crash!pro-generic!sb@nosc.mil INET: sb@pro-generic.cts.com
ericmcg@pro-generic.cts.com (Eric Mcgillicuddy) (12/06/89)
In-Reply-To: message from sb@pro-generic.cts.COM Could someone explain how the TWGS works? Without giving away trade secrets does it cache memory and run at full speed when in the cache? Assuming this is correct, how large is the cache and can it be made larger? (I don't recall seeing any memory chips in the ads). Steve: The 12v is already regulated out of the power supply, so I would say go for the simple. Might not be the case for third party PS, but Apple's look good to me. (can also retain power for a bit, had a half second power outage and the computer didn't even flinch. Monitor faded and came back though)
pa1017@sdcc13.ucsd.edu (Nick Lenz) (12/08/89)
ericmcg@pro-generic.cts.com (Eric Mcgillicuddy) asked about the size
of the TWGS's cache.
Well, I think that the standard cache size is 8 K, but it IS
possible to increase the size, though it isn't necessarily easy.
Bill Heineman has his TWGS (already running at 13Mhz) modified so he
has a 32K cache. He said that it increases the speed quite a bit,
but it the chips needed for it are still relatively expensive. Also
he had to make his own circuit board for it. Maybe when the prices
of the chips come down, AE might offer an upgrade.
Nick Lenz
"How would you feel about life if
Nick Lenz
"How would you feel about life if Death
Internet: nlenz@ucsd.edu was your older sister?" -- _Sandman_
GEnie: N.LENZsb@pro-generic.cts.com (Stephen Brown) (12/18/89)
In-Reply-To: message from ericmcg@pro-generic.cts.com You favour getting the 65816's 6 volts from a resistive divider? This assumes that the current it draws is the same for all operations, and I don't know if this is safe to say. As the current drawn by the '816 changes, so will its supply voltage, unless the resistive divider is very robust (in terms of current) indeed. Since a 13 megahertz 65816 is going to be a pretty penny (does anyone know how much, in small quantity?), I'd probably spring for the two-buck regulator. UUCP: crash!pro-generic!sb ARPA: crash!pro-generic!sb@nosc.mil INET: sb@pro-generic.cts.com