söndag 22 juli 2018 skrev Paul Birkel <pbir...@gmail.com>: > 26 bits (or 13 bits) doesn't make any sense on a 16-bit machine; makes > more sense as a high-speed I/O buffer.
One can note that it is actually two different types of 1k chips. 16 chips are 94L415 and 10 chips are 93415. As far as I understand the L is the slower variant. This could mean that 16 bit data is in the L chips while the faster chips are used for a 10 bit cache tag. Maybe 8 address bits plus some valid bit and possibly a dirty bit? The switch is marked ON/OFF which could simply cache on/off. The handwritten label on the board says that it is not in use and should sit in slot 21. And of course those two I/O connectors don't belong on a cache. Those IO connectors are connected to two double height boards in 26 /27 AB. They are also made by ACT and contain a few TTL chips. So it pulls out some signals out of both Unibuses but 20 + 10 signals at most it not much of a complete bus so I wonder what kind of signals go there. > While odd to use slot 21 (Fastbus) for something other than memory I don't > know why a fast memory-mapped I/O channel couldn't go there. > Also note all of the signals employed on tabs C-D-E-F? > It may not even employ the Fastbus; just talk to Unibus B. > Unfortunately there's not much documentation for the MS11. > It seems likely that A-B isn't anything like the usual Unibus signals, and > who knows where the Fastbus signals are routed. > On my backplane D-E are essentially unused whereas A-B-F are busiest. > > I see the marking "copyrighted 1976", which is rather earlier than the ACT > / ABLE documentation online. > > From Bitsavers see the ABLE documents for the SCAT/45: > Able_Computer_Product_Summary.pdf - page 3 > Able_Computer_Product_Brochures_1982.pdf - pages 16-17 > > The PN 10003 doesn't seem to match anything documented from ACT, however > it's consistent with them. > The original QBus Univerter is PN 10001, and is dated 1976. There are some documentation to get with the machine so the manual for the board might turn up. > > What are the pair of DIP24 ICs on the lower-left? Fairchild 9308 Dual 4 bit latches. > > -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Paul > Anderson via cctalk > Sent: Saturday, July 21, 2018 6:54 PM > To: Mattis Lind; General Discussion: On-Topic and Off-Topic Posts > Subject: Re: Strange third party board in PDP-11/45 > > I think it's Applied Computer Technologies, and I think they made cache > and several other options. They were popular back in the day. I have a > bunch of their boards here. > > Paul > > On Sat, Jul 21, 2018 at 1:37 PM, Mattis Lind via cctalk < > cctalk@classiccmp.org> wrote: > > > This board was sitting in slot 21 of the backplane in a 11/45 > > > > https://i.imgur.com/ZYWZQCo.jpg > > > > What kind of board is this? > > > > It has 26 bipolar RAMS. Fairchild 93415 1kbit SRAM. > > > > The manufacturer might be ACT whatever that is. > > > > My guess is that it is some kind of cache board? It is connected to both > > unibuses in the machine. > > > > Better ideas? Documentation? > > > > /Mattis > > > >