From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <39414877.FA50B3DB@motorola.com> Date: Fri, 09 Jun 2000 14:41:43 -0500 From: "Richard Hendricks" MIME-Version: 1.0 To: "'linuxppc-embedded@lists.linuxppc.org'" Subject: Re: Running the 823 FADS board @ 72 MHZ References: <319E391E2049D311843500609457383D07FC48@exchange.vividimage.com> <39413DC8.C2BE7490@motorola.com> <394140BA.F2D0FD3B@ccrl.mot.com> Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Most PC100 memory has a Cl latency of 8ns. The MPC8xx family has a setup-time of 6ns. This gives a maximum frequency of 1/(8+6ns) = 71MHz. I have recently seen "PC100" memory with a Cl latency of 6ns, which gives you 83 MHz. After talking with the design team, they say the setup time is probably closer to 5.4ns in real-life, which gives 74MHz and 87MHz (theoretically, only looking at setup-time). This assumes, of course, no trace delays or excessive bus capacitance. I wouldn't productize a design that used its memory outside of spec. It is fun to play with though. Steve Rossi wrote: > > I've got a custom 823 board running on the bench at 80MHz 1:1 with PC100 SDRAM > with no problems but I had to re-program the UPM to do it. 50MHz is a sweet spot > (at least with my memories), but above 50MHz without re-programming the UPM > you're probably violating SDRAM timing somewhere. > > Steve > > Richard Hendricks wrote: > > > I do not know of any *development* board that is running the faster > > speed CPU's in 1:1 mode. I *do* know several customers are running > > their designs at 66 MHz 1:1. There is also at least 1 customer I > > know of running 75 Mhz 1:1 without problems. I wrote an application > > note describing how to do a high-speed SDRAM interface to the MPC823. > > Hint: PC66 will NOT work at 66 MHz. PC100 in most cases won't even > > work at 75 MHz. If you are interested in the app note, I recently > > published it on comp.sys.powerpc.tech > > > > Kirk Haderlie wrote: > > > > > > Are you aware of a development board that is running the faster speed CPU's? > > > We need the faster speed for our application. > > > > > > -----Original Message----- > > > From: Richard Hendricks [mailto:richard.hendricks@motorola.com] > > > Sent: Friday, June 09, 2000 9:44 AM > > > To: 'linuxppc-embedded@lists.linuxppc.org' > > > Subject: Re: Running the 823 FADS board @ 72 MHZ > > > > > > The FADS board are not designed to run at that speed. Just for kicks, > > > I've tried seeing how fast I can go without problems. At about 60 MHz > > > the SDRAM no longer works, and 68 MHz the DRAM starts not working. This > > > is with the default 50 MHz tables. With better tuning, it may be > > > possible > > > to go higher, but I doubt you could reach 72 MHz with the FADS. > > > > > > Kirk Haderlie wrote: > > > > > > > > We are trying to run the FADS board @ 72MHz and enjoying the infamous UPM > > > > tables. Has anyone successfully run the FADS board at this speed and if > > > so > > > > would you be willing to share your UPM tables. We are trying to set them > > > > up for the SDRAM and 60-ns EDO DRAM. > > > > > > > > Kirk Haderlie > > > > kirk@vividimage.com > > > > Vivid Image Engineering > > > > > > > > > > -- > > > MPC823 Applications Engineering Development > > > Get help from other MPC823 customers on the > > > comp.sys.powerpc.tech newsgroup! > > > > > > > -- > > MPC823 Applications Engineering Development > > Get help from other MPC823 customers on the > > comp.sys.powerpc.tech newsgroup! > > > > -- > ------------------------------------------------------- > Steven K. Rossi srossi@ccrl.mot.com > Staff Engineer > Multimedia Communications Research Laboratory > Motorola Labs > ------------------------------------------------------- -- MPC823 Applications Engineering Development Get help from other MPC823 customers on the comp.sys.powerpc.tech newsgroup! ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/