so far off topic - capatob - saratov2 computer Russsian pdp8?

[allison]

On 01/07/2019 07:25 PM, ben via cctalk wrote:
> On 1/7/2019 8:20 AM, allison via cctalk wrote:
> snip...
>> made though more likely 74F, AS, or LS variant and of course CMOS 74ACT
>> (and cmos friends) as I just bought a bunch.  Dip is getting harder to
>> get but
>> the various SMT packages are easy.  Prices for 10 or more of a part are
>> cheap to cheaper from primary suppliers.  The second tier suppliers are
>> often several times that.
>
> I got ebay... The bottom of the heap.
>
>> I figure most of what I did back then is years before many here were
>> born.
>>
>> However I have enough NOS TTL 74LS, 74AS, 74F series to build several
>> machines.
>
> I have been playing around with a early 70's TTL computer design
> and 74LS181's are too slow by 30 ns. Using a BLACK BOX model for core
> memory, I can get a 1.2us memory cycle using a 4.912 MHz raw clock
> but I need a few 74Hxx's in there. Proms are 256x4 60 ns and 32x8 50 ns.
>
> Do you have your 74Hxx spares? Eastern Europe still  has a few on ebay
> with reasonable shipping for 100% American Russian parts.
>
No use for 74H parts though I have a bunch.

the 74LS are slow  you are paying for lower power with speed.  tHe 74181
and 74S181 were far faster.

Proms are small and slow, last time I used them was for the address
decode used on the Northstar* MDS-A controller.

I built the last big machine with ram back 1980 and was in the 1us
instruction
cycle time for single cycle instructions without pipelines.  Core was never
considered.  Trick is throw hardware at it.  Adding adders to the address
calculation rather than reuse the ALU saves a lot of time and wires.   Not
like it was for manufacture or anything like that.  More of an exercise.

I still want to make a stretched 8, PDP8 ISA with 16 bits and faster.
No good reason save for it wold be fun.
>> I'm still building, current project is a very compact Z80 CP/M system
>> using CF
>> for disk. Mine uses all Zilog CMOS for very low power.  Its a variant of
>> the
>> Grant Searle Z80 with memory management added to utilize all of the
>> 124k ram and eeprom.  If you want go look there.
>
> What do you use all that memory for?
>
CP/M the allocation block store for each drive and deblocking buffers
for performance
can be large plus its easy to hide part of the Bios in banked ram. 
Background processes
are easier when you have lots of ram for that.  Most of the larger aps
like C compilers
and such run better with more than 48K, 56k is easy, and 60k is doable
with the
right memory map.

For EEprom its more than boot, the system is in EEprom (about 8K) and
with 32K
or more things like romdisks and utilities are easily parked there.

I've been building nonstandard CP/M systems since 79.  In all cases he
aps think
it is standard CP/M but the bios and such have been tuned even CP/M Bdos
it self.
Though I often use ZRdos or ZSdos as they are very good.  Not much you
cant do
to it.

Allison
>>
>
> The Chinese elves have been busy, My 5V 15 amp $20 power supply arrived
> in the mail today. I have power to spare for my BUS and blinking lights.
>
So long as you load it at least 10% it will be good.

> Ben.
>
>