Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!TOPS20.RADC.AF.MIL!GUBBINS From: GUBBINS@TOPS20.RADC.AF.MIL (Gern) Newsgroups: comp.sys.zenith.z100 Subject: Re: Linking 2 PCs Message-ID: <12549266060.9.GUBBINS@TOPS20.RADC.AF.MIL> Date: 11 Dec 89 15:37:20 GMT References: Sender: daemon@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 25 So what's the problem of running a Z-100 at >10MHz? They can run very nicely at 10.7MHz. Standard new motherboard with ZDS factory 256K DRAM 8MHz or new motherboard with HA-108 chip upgrade. 150nsec 256K DRAMs work okay, but I feel better with 120nsec. Just replace the 8088-2 with a 8088-1 (10 MHz) and up the crystal to 32MHz, also replace all NEC ICs except the keyboard controller (and I don't trust that) with non-NEC brands if there are any in your machine. DO NOT USE a V20 CPU at any rating. The 10.7MHz Z-100 will now blow timming windows in the Z-100 RS-232 and floppy controller diagnostics - this is a fault of the diagnostic software using loops to time events that are now too short. All other diagnostics will run normally. I can make available at cost PC Boards for a baby-board assembly so you don't hack the Z-100 crystal on the motherboard. The device is a PCB, wire-wrap socket, resistor, crystal oscillator, two wires to a toggle switch on the rear panel. You get the 8MHz from the motherboard one way, throw the switch and get the speed from the oscillator the other way. You remove U236, stick it in the device and put the device in the socket that you removed U236 from. If you socket the oscillator, you can safely experment with system speed increases, using the motherboard 8MHz to fall back on. Cheers, Gern -------