yah nothing like some crappy weather to give me time for hobbies. I've noticed this trend that October and November are good months for m100 and me.
I have really been working hard on perfecting quad also, unfortunately at the expense of the bom. But I think I have a really good solution to the issues. I'll have to post a summary once I have things tested out. I just wish Oshpark could do better than 15 days from board order to boards in hand. On Tue, Nov 14, 2017 at 2:12 PM, Mike Stein <[email protected]> wrote: > Good stuff; sounds like you've been busy! > > m > > ----- Original Message ----- > *From:* Stephen Adolph <[email protected]> > *To:* Model 100 Discussion <[email protected]> > *Sent:* Monday, November 13, 2017 10:29 PM > *Subject:* Re: [M100] new project > > update- > I have gotten REXCPM working on my bench. I built the first unit with just > 1MB of SRAM, while it is capable of 2MB. > I am able to bank switch, read and write. That's pretty much it. I have > some additional verification to do still, and making sure that the SRAM is > protected during power cycles adequately. > > I'll probably build another and ship it to New Zealand so Phil can port > CP/M onto it, and create those much needed SRAM drives. > > ..Steve > > On Wed, Oct 25, 2017 at 5:40 PM, Stephen Adolph <[email protected]> > wrote: > >> I met up with Phil Avery recently in person, which was a real hoot. In >> the process I got a front row demo of a T102 running CPM. Very cool! Now, >> this T102 was special as it was equipped with a Remem - which provides very >> flexible flash/ram storage. Specifically, 4MB of flash and 2MB of SRAM. >> >> What's important here, is that that big pile of SRAM makes for 2 very >> fast RAM disks for CPM. >> >> Phil and I discussed the challenge of how to make CPM more obtainable. >> Remem was cool, but never easy to install and awful to build. Keeping the >> serial port free is also nice as it allows for the link to the outside >> world. >> >> So, where we landed was that an all-SRAM REX could make CPM more >> achievable, as it would provide not only ram in the critical 0000-7FFF >> memory space, but also supply ramdisk via bank switching in/out of the >> optrom bank. >> >> Large SRAM chips (meaning 1MB or bigger) tend to be 3.3V IE they need to >> be buffered to use them in M100-land. >> >> Anyhow, long story short, I am awaiting 3 "REXCPM" board now, which look >> a lot like REX except with a 2MB SRAM chip, extra buffer chips, and 3 wires >> that need hookup to the M100. Kinda like (exactly like) a mega-EXTRAM. >> >> Back in the day, there was a product called EXTRAM that put RAM in the >> optrom socket - 32kB. Then there was XR4, which was EXTRAM x 4 or 128kB in >> the optrom socket. XR4 used the IO/M signal to allow PORT based bank >> selection. Here, REX is instead listening for an unlock sequence on the >> address bus to enable bank selection. >> >> I think EXTRAM used 2 wires - Vnicad, /WR >> I think XR4 used 3 wires - Vnicad, IO/M and /WR. >> REXCPM plan is to use 3 wires - Vnicad, /WR and RAMRST. >> >> RAMRST may or may not be needed. That signal is intended to protect >> memory during power down. Perhaps the developer of XR4 found an >> alternative way to protect the memory. Anyhow if I can eliminate RAMRST I >> will. Anyone have any thoughts on the subject? >> >> In practice this would install the same way as REX2- >> In M100 - 3 wires over to the system bus socket >> in T102 - 3 wires over to an adjacent RAM chip >> in NEC - 3 wires over to a memory module. >> >> Losing power would wipe the card..so that's a big difference from REX. >> >> Having said that, SRAM does have advantages, and in principle one could >> have many of the same REX features working on REXCPM - memory backup, >> option roms etc. >> >> anyhow, that's the update. >> >> Steve >> >> >> [image: Inline image 1] >> >> >> >> >> >
